Обработка дерева от влаги: Лучшая защита древесины от влаги и гниения — общая информация

антисептики, морилки, лаки и другие вещества с защитными свойствами

Один из популярных вариантов отделки поверхностей деревянного дома или дачи – обшивка тонкими дощечками, известными под названием вагонка. В результате комнаты приобретают уютный вид, позволяющий расслабиться в здоровом, экологически безопасном окружении.

Обеспечить сохранность интерьера в неизменном виде на протяжении длительного времени помогает пропитка для вагонки внутри дома, которую можно приобрести в специализированных магазинах и нанести в соответствии с указаниями производителей. Есть и другие средства, которыми можно покрыть дерево.

Не забудь поделиться с друзьями!

Содержание статьи

Зачем использовать пропитку?

У некоторых владельцев возникают сомнения в необходимости пропитки вагонки из дерева внутри загородного строения. Если дощечки не покрыть, через некоторое время на них будут заметны изменения. При слабой вентиляции на вагонке появится синева, в результате интенсивного солнечного освещения она может стать темно-серой.

Синева объясняется действием микроорганизмов, от которых можно будет избавиться с помощью активных окислителей, например хлора. Процедура не очень легко выполнима и сопровождается выделением неприятного запаха.

Посеревший от солнца налет можно снять механической шлифовкой вагонки, но положительного эффекта хватит ненадолго. Целесообразнее проводить обработку сразу после окончания отделки, чтобы потом не иметь проблем.

К тому же покрытие преображает древесину, делает интерьер особенным. Вагонка, покрытая водостойкой пропиткой, может дольше прослужить даже в нерегулярно отапливаемом, сыром помещении.

Виды составов

Чем покрывать вагонку внутри дома – легко решаемый вопрос, потому что в продаже имеется множество средств для разных климатических зон и типов строений.

Композитные пропитки предназначены для выполнения нескольких функций, главными из которых являются следующие:

• понижение горючести,
• защита от микробов,
• улучшение внешнего вида,
• повышение механической прочности.

Существуют средства, предназначенные в первую очередь для защиты вагонки, и составы, созданные для декоративного эффекта. Многие препараты в равной мере успешно выполняют несколько функций.

Чем лучше обработать?

В продаже имеется большое количество средств для обработки древесных материалов. Информация о наиболее популярных препаратах поможет легче выбирать покупку потенциальным покупателям.

Антипирены

Вагонку, расположенную внутри дома рядом с нагревающимися устройствами, нужно защитить от возможного воспламенения. С этой целью используют антипиреновые пропитки, самостоятельно нанести которые непросто.

Гораздо удобнее купить вагонку для дачи, заранее пропитанную противопожарными веществами. В помещениях с концентрацией влаги, не превышающей 70 %, вагонку можно покрыть растворами с умеренной устойчивостью. Внутри дома нанесенный состав сохранится надолго, стоит он гораздо меньше, чем атмосферостойкий раствор.

Антисептики

Сильным фактором риска порчи древесины является микробиологическое воздействие. От него избавляются с помощью антисептиков. Антимикробные растворы, которыми можно пропитывать древесину, справляются с биологическими загрязнениями, предотвращают появление новых очагов плесени и гниения. У антисептиков бывает резкий запах, который долго не выветривается, и на это надо обращать внимание при покупке, изучив отзывы о товаре.

Препараты с большей стоимостью, чем обычные дезинфицирующие вещества, могут не только защищать от микроорганизмов, но и одновременно улучшать эстетическое впечатление, увеличивать способность к отталкиванию молекул воды.

Морилки

Специальные жидкости на основе воды, спирта или органических растворителей, которые проникают вглубь древесины, создают определенный цвет или оттенок, называют морилками. У термина есть иностранный синоним – бейц. Растворы не защищают, а только тонируют дерево, хотя существуют особые виды дорогих морилок с выраженным защитным действием.

Обратите внимание! В любом случае после нанесения на вагонку внутри дачи морилки сверху ее нужно покрыть лаком. Иначе дерево не сохранит первозданный вид.

Иногда на древесных дощечках имеются темные пятна, появление которых остается загадкой. Обработать такие места можно отбеливателем, хорошо подобрав концентрацию и время выдержки. Можно потренироваться на отходах вагонки, посмотреть, на сколько тонов происходит осветление древесной основы, и сделать соответствующие выводы.

Лаки

Хорошее защитное действие по отношению к вагонке внутри дачи или жилого дома оказывают лаки. Ими же можно покрыть вагонку для достижения декоративного эффекта. Лаковые составы на основе акрилов хорошо украшают поверхность, создают на ней биологический барьер.

В связи с минимальной аллергенностью внутри помещения имеет смысл использовать аквалак. Он дольше сохнет, чем растворы в органических жидкостях, но обладает большей безопасностью для здоровья. Аквалаками можно создавать полностью или слегка матовую, а также глянцевую поверхность.

Если к растворам добавить колер, получится окрашенное средство с желаемым оттенком. Снаружи такой состав долго не удержится, поэтому не рекомендован для уличного применения. Лаки на основе воды создают барьер для проникновения пара, исключая загрязнение открытых пор.

Обратите внимание! В некоторых модификациях аквалака присутствуют добавки антимикробного действия, что значительно улучшает сохранность вагонки внутри дома.

В другие композиции введены вещества, нивелирующие влияние УФ-лучей. Такими составами имеет смысл покрыть стены, освещаемые солнцем в течение большей части дня.

Огромной стойкостью обладают алкидные лаковые растворы, после высыхания которых покрытие может сохраняться на протяжении 10 лет. Обычно внутри деревянного дома, дачи такими составами рекомендуют покрывать полы. Любителям постоянных цветовых решений комнат можно наносить алкидные лаки на стены. Если желание изменить интерьер возникает раньше, можно сверху распределить лак другого цвета.

Краски

Для покрытия вагонки внутри дачи может применяться огромная группа разнообразных красок для дерева.

«Ветераном» рынка являются масляные краски всех цветов и оттенков, которые держатся на сухой поверхности более 7 лет. По истечении срока красочный слой может обесцвечиваться и отслаиваться, тогда покраску придется повторить. Улучшает закрепление пигментов на древесине предварительная обработка основы олифой. Высыхающие растительные масла покрывают все поры полимерной пленкой, которая ухудшает паропроницаемость, зато улучшает качество покрытия.

Обратите внимание! Масляные краски – самый дешевый материал для покрытия вагонки, имеющий недостатки.

Из-за закупоривания естественных пор дерева ухудшается микроклимат внутри помещения. При покраске происходит активное испарение растворителя, имеющего неприятный запах. Пары органической жидкости вредны для здоровья, поэтому покраску можно проводить только летом при открытых окнах и дверях.

Акрилатные краски тоже сделаны на резко пахнущей основе, покраску нужно проводить осторожно, при тщательном проветривании комнат. Наносится акрилатная краска быстрее и легче, чем масляные составы, образует упругое, эластичное покрытие, которое держится долго и прочно. Стены внутри дачи, покрашенные акрилатами, хорошо переносят зимние холода даже при отсутствии отопления длительное время.

Масла и воски

Помимо олифы, которую делают из высыхающих масел, для покрытия вагонки внутри дачи применяют другие масляные составы, хорошо поглощаемые древесиной. Они формируют матовую или блестящую поверхность при аккуратном втирании и последующей полировке. Подобную химическую структуру имеют воски, отличие заключается в замене глицерина сложного эфира на высший одноатомный спирт.

Воски обладают очень большой стойкостью, образуют блестящую ровную поверхность при правильном распределении и нанесении на вагонку. Восковые покрытия могут сохраняться десятилетиями в случаях отсутствия больших механических нагрузок. Восковая лазурь продается в состоянии, готовом к применению. Твердые воски перед нанесением нужно размягчить расплавлением на водяной бане. Чтобы воск распределился равномерно, вагонку следует предварительно загрунтовать.

Хороший результат получится, если покрыть доски смесью воска с маслами, сочетающими достоинства обоих компонентов.

Особенности нанесения пропиток

Существует несколько видов вагонки, они отличаются количеством и формой стыков на образующейся поверхности. В зависимости от этого понадобится разное количество усилий для ее подготовки.

В любом случае, прежде чем покрыть вагонку любым средством, надо внимательно просмотреть все дощечки. При наличии темных пятен проводят локальное осветление отбеливателем. Затем всю поверхность можно слегка промыть разбавленным раствором соды, дождаться полного испарения воды. Только после этого можно обрабатывать дерево грунтом и основным составом либо сразу пропиткой.

Трещины замазывают шпатлевками для дерева, все тщательно зачищают наждачной бумагой.

Для более эффективного закрепления декоративного слоя древесину подвергают грунтовке. Очень внимательно нужно распределять грунтовочную массу в швах. Для нанесения грунта по основной части площади можно пользоваться краскопультом, в местах стыка лучше грунтовать кистью.

Каждое средство имеет свои особенности нанесения, которые обязательно описаны в рекомендациях производителя. Сопроводительные документы нужно хорошо изучить, подготовить составы в соответствии с указаниями. Все средства наносят в несколько этапов; каждая следующая стадия может выполняться только после высыхания поверхности, при этом завершающий слой должен быть самым тонким. Выполнение этих правил поможет получить надежное и красивое покрытие.

90000 Moisture properties of wood | Wood Products 90001 90002 Wood is a hygroscopic, meaning it is a material that absorbs water. Water gets into wood in three ways: as a fluid through the cell lumens through capillary tension, as vapour through the cell lumens, and as molecular diffusion through the cell walls. The moisture content of wood means the relationship between the mass of water in it and the mass of the timber without the water. (For example, if a piece of wood weighing 100 kg contains 50 kg of water, the moisture percentage is then 100%).The moisture content of newly sawn wood is usually 40-200%. In normal use the moisture content of wood varies between 8% and 25% by weight, depending on the relative humidity of the air. 90003 90002 The equilibrium moisture content of wood is a state corresponding to the air temperature and relative moisture, in which the moisture content of the wood remains steady. It should be noted about the equilibrium moisture content of wood that it is determined by the relative humidity of the air, not its absolute humidity.Relative air humidity is the ratio of the amount of water in the air to the maximum amount of water that the air could hold at the prevailing air temperature. Pre-dried timber reaches its equilibrium moisture content in a couple of weeks. The saturation point of wood grain means the ratio of moisture in the wood when the cell walls are saturated with water, but no free water appears in the cell lumina. As it dries, wood begins to contract, when its moisture content falls below saturation point.Correspondingly, as wood gets wet, expansion ends at the saturation point. In the main Finnish tree species, saturation point at +20 C is about 30%. Wood’s ability to absorb and release moisture (moisture capacity) can be used as a structural benefit, for example by using wood-based thermal insulation in construction, which balances the movement of moisture in the structures. 90003 90002 Wood contracts and expands in different ways in the radial and tangential directions of the growth rings and in the direction of the grain.This phenomenon goes by the name anisotropy. As it dries, wood shrinks from being completely wet to absolutely dry, in the tangential direction by an average of 8%, in the radial direction by about 4% and in the direction of the grain by only 0.2-0.4%. Heartwood is always drier than surface wood, which makes wood drying challenging. Anisotropy and the internal tensions of wood are also caused by the warping of the wood as it dries. The moisture dynamics of wood must always be taken into account in construction.The moisture dynamics may cause, for example, the frame of a building to sink in the middle. Furthermore, the great shrinkage of wood in the tangential direction causes large-sized timber to crack. Wood usually cracks in the place where the distance from the surface to the core is shortest. 90003 90002 As the density of wood increases, the shrinkage and expansion caused by moisture usually increase. As wood dries, its strength properties improve. For example, the compression and bending strength of wood increase by about two-fold as wood dries from fresh to 12-15%.The tensile strength of wood is at its greatest in the 6-12% moisture content range. As wood dries, its strength properties improve significantly when the moisture content falls below the saturation point of the grain. In the dimensioning of wooden structures, too, the moisture content of wood must be taken into account, because it affects the strength of the wood. 90003 90002 Wood begins to suffer damage if its moisture content remains at over 20% for long periods of time. The relative humidity of the surrounding air is then usually about 80-90% or more.Wood begins to go mouldy within a few months if the relative humidity of its surrounding air remains at more than 80% during this time. The 70% relative humidity of air can be considered as a critical value. When the relative humidity of the air exceeds 90%, wood begins to rot. A prerequisite for the moulding and decaying of wood, however, is for the temperature to be between +0 and + 40 C. Although in sub-zero temperatures the relative humidity of air may be more than 85% for long periods, wood does not suffer damage, because the temperature is insufficient for fungus and decay to develop.In order to thrive, fungal spores and rot fungus also need oxygen and nutrients, of which there are usually plenty both in the wood and in the surrounding air. 90003 90002 Fungus can not penetrate deeper than the surface of the wood, so it is not harmful from a point of view of the strength of the wood. The spores spread by the fungus are, however, harmful to health, because they can give people different allergic reactions and mild symptoms of poisoning, such as a continually runny nose, dizziness and headaches.Because of this, the occurrence of mould must always be taken seriously. The weathering of wood is often mistakenly compared to it going mouldy. The weathering of wood is pigmentation caused by blue stain, which also reaches deeper into the structure of the wood. Blue stain spreads as spores or as mycelial growth and is particularly prevalent in CO2-storing conifers. Blue stain can not develop at a temperature of less than +5 C. Weathering does not essentially affect the strength of wood. 90003 90002 90015 The dependence of the moisture content of wood products on temperature and the relative humidity of the air 90016 90003 90002 Example of the application (red dotted line) 90003 90002 — Source data: 90003 90002 — indoor air temperature + 22 C 90003 90002 — relative humidity of indoor air RH 50% 90003 90002 The table shows that the moisture content of wood is about 9.5% in the case based on the source data 90003 90002 90003 .90000 What Are Acceptable Moisture Levels in Wood? 90001 90002 Understanding Moisture Content in Wood 90003 90004 How Does Moisture Affect Wood? 90005 90006 90007 Everyone who works with wood needs to understand how wood interacts with moisture in the environment. Whether you’re a woodworker making cabinets, a wood flooring professional installing hardwood floors, or if you use wood in construction, 90008 wood moisture content (MC) 90009 should be always on your mind.90010 90006 Wood is hygroscopic. It gains or loses water moisture as the relative humidity (RH) of the surrounding air changes. 90010 90006 These varying humidity levels of the surrounding air cause wood to not only gain or lose water moisture but to expand or shrink as well. As the humidity increases, the MC increases, causing the wood to expand. As the humidity decreases, the MC decreases, causing the wood to shrink. When the wood neither gains nor loses moisture, we say that the wood has reached its equilibrium moisture content (EMC).90010 90006 According to Dr. Eugene Wengert, professor and specialist in wood processing at the University of Wisconsin-Madison’s Department of Forestry, wood should be dried to a water MC that’s within two percentage points of the EMC where the wood is going to be used. 90010 90006 Before we explain what this means, let’s make sure we have our definitions down. 90010 90019 90020 MC = the wood’s moisture content 90021 90020 The EMC (equilibrium moisture content) of the location where the wood is at the moment or the location of where the wood is going to be used = the MC that the wood will eventually attain if it’s placed in that location.90021 90024 90006 If this is confusing, do not worry. The chart below will clear things up. Notice that the EMC of the in-use location is the 90008 same 90009 as the MC: 90010 90029 90030 90031 90032 Humidity of the in-use 90033 location 90033 90035 90032 EMC of the in-use location 90035 90032 Corresponding MC the wood will attain at this location 90035 90040 90041 90042 90031 90044 19-25% 90045 90044 5% 90045 90044 5% 90045 90040 90031 90044 26-32% 90045 90044 6% 90045 90044 6% 90045 90040 90031 90044 33-39% 90045 90044 7% 90045 90044 7% 90045 90040 90031 90044 40-46% 90045 90044 8% 90045 90044 8% 90045 90040 90031 90044 47-52% 90045 90044 9% 90045 90044 9% 90045 90040 90083 90084 90006 So, using this chart, we know that in an area of ​​the country where the RH inside a home or office is anywhere from 26-32%, both the EMC of the in-use location and the wood moisture content kept in that location will be 6%.90010 90006 This means that wood intended for interior use in this location should not only be dried to around 6% but should be kept at this moisture content both before and during the manufacturing process. 90010 90006 So, the wood must always be allowed to acclimate or come into balance with the RH of the end-use location. Failure to do this will result in warping, cracking, and other problems after the construction of the wood product. 90010 90002 How Do You Remove Moisture From Wood? 90003 90004 Kiln Drying 90005 90006 Freshly cut wood has a lot of moisture in it.Eventually, this internal moisture will evaporate by itself. However, kiln drying is used to speed up the process. Some of the unfinished wood you see on the market has been kiln-dried to reduce its water moisture content to around 8% so that it will not suffer from moisture-related defects like warping and buckling. However, many building materials may have been dried down to about 15% moisture content. 90010 90006 But, that’s not the end of the story … 90010 90006 Wood moisture content is always varying.It’s never constant. Wood — freshly cut or kiln-dried — is always interacting with environmental moisture. Therefore, just because the wood is kiln-dried does not mean it has lost the ability to absorb moisture. It will continue to absorb and release moisture until it comes into balance with the surrounding air. 90010 90002 What are Acceptable Moisture Levels in Wood? 90003 90006 The acceptable moisture levels of wood and lumber are in the range of 6% to 8% for interior and 9% to 14% for exterior wood or for building envelope components within constructed assemblies.The acceptable moisture content in wood depends on two factors: 90010 90019 90020 The wood’s final use. 90021 90020 The average RH of the environment where the wood will be used. 90021 90024 90006 These two factors make it difficult to say anything specific about acceptable wood moisture content. It’s more important to understand that the wood is kiln-dried down to a certain bell-shaped 90008 range 90009 of MCs. There will be statistical outliers on both the low and the high end and you’ll want to catch these by using a quality moisture meter.90010 90002 How to Measure Moisture Content in Wood? 90003 90006 There are two main ways of measuring wood moisture content: oven-dry testing and moisture meter testing. Let’s go over the basics of each … 90010 90004 1. Oven Dry Testing 90005 90006 Oven dry testing is the oldest method for measuring the moisture content of wood. The process is time-consuming but produces accurate results if followed correctly. Here’s how it works … 90010 90006 The wood sample being tested is dried in a special oven or kiln and its weight periodically checked.Once the wood sample’s weight stops changing, its weight is compared to what it was before the drying process began. This weight difference is then used to calculate the wood’s original moisture content. 90010 90006 While oven-dry testing, if followed correctly, offers accurate results, there are a few drawbacks: 90010 90019 90020 90008 It takes a long time 90009 — We’re talking about hours. The oven drying process must be done slowly or the wood could burn and the test results will be worthless.90021 90020 90008 It will render the wood unusable 90009 — It often happens that oven drying over dries the wood to the point where it’s unusable. 90021 90020 90008 It requires a special oven or kiln 90009 — Most hobbyists who work with wood do not have an oven that’s capable of producing accurate results. 90021 90024 90006 These three drawbacks mean that oven-dry testing usually is not the option of choice for hobbyists who work with wood. 90010 90004 2. Moisture Meter Testing 90005 90006 The fastest way to test the moisture content of wood is to use a moisture meter.There are two main types of wood moisture meters, pin-type and pinless. 90010 90147 Pin-type Wood Moisture Meters 90148 90006 Pin-type meters use penetrating electrodes and measure the wood’s moisture content using electrical resistance. Since water conducts electricity and wood does not, the dryness of the wood can be determined by the amount of resistance to an electrical current. Dryer wood produces more resistance than wetter wood. 90010 90147 Pinless Wood Moisture Meters 90148 90006 Pinless meters are non-penetrating and read the moisture content via a non-damaging electromagnetic sensor that scans the wood.Because pinless meters scan the wood’s surface and cover a larger area than pin-type meters, they provide a more thorough picture of the wood’s moisture content. 90010 90006 Pinless meters also do not leave damaging pinholes on the wood’s surface. This makes pinless moisture meters perfect for measuring the moisture content of things like expensive hardwood floors. 90010 90002 How to Measure Moisture Content in Wood with a Moisture Meter? 90003 90004 Pin-Type Moisture Meters 90005 90006 The general process for using pin-type moisture meters is as follows … 90010 90019 90020 Insert the pins into the surface of the wood you want to test.90021 90020 Make sure they’re aligned with the grain and not across it. 90021 90020 Turn on the meter. The electrical current will then move from pin to pin and measure the resistance encountered. 90021 90024 90004 Pinless Moisture Meters 90005 90006 Pinless moisture meters are even easier to use. Just press the scanning plate against the wood’s surface, turn on the meter, and receive the reading. 90010 90006 Shop Wood Moisture Meters 90010 90002 How Accurate Are Wood Moisture Meters? 90003 90006 The ASTM D4442 standard determines the accuracy of wood moisture meters.This method uses the oven-dry method and then compares the results to those obtained using a moisture meter. The difference is the moisture meter’s measurement error. 90010 90006 For more information, see our article comparing Pinless Moisture Meters vs. Pin Meters. 90010 90002 Moisture Content of Wood from a Woodworker’s Perspective 90003 90006 Because wood shrinks and warps as it dries, woodworkers want it to be pre-shrunk before they use it. Furniture maker Lonnie Bird weighs in, 90010 90006 «I do not want the wood to shrink after I use it because the wood will warp or split.»90010 90006 Bird, who runs the School of Fine Woodworking outside Knoxville, Tennessee, says he knows wood shrinks seasonally but wants to minimize the shrinkage and expansion by drying the wood to a moisture content of about 8%. 90010 90006 To make sure the wood is properly dried, he always uses a moisture meter before working with it. 90010 90006 The moisture content of freshly cut wood is typically somewhere between 40-200%. If you’re wondering how wood can have a 200% moisture content, here’s how that works … 90010 90006 Because the moisture content of wood is equal to the weight of the water in the wood divided by the weight of the wood without the water, it’s possible for the moisture content to exceed 100%.In other words, the water weighs more than the wood fibers. 90010 90004 How Dry Should Wood Be for Woodworking? 90005 90006 The normal moisture content of wood (or EMC) varies from 7% -19% depending on the RH in the air. 90010 90006 For woodworkers who build cabinets, fine furniture, musical instruments, dishes, toys, decorative art, boat restoration, or various other wood products, the acceptable wood moisture content normally ranges from 6% to 8%. 90010 90006 However, this range will vary slightly according to the geographic region because of varying RH levels.90010 90006 If an interior location has an average RH of 40-52%, wood placed there will have an average EMC of 8-9%. This is based on a chart in Wood Handbook: Wood as an Engineering Material. 90010 90006 Therefore, in order to avoid post-construction problems, a woodworker building a cabinet for this particular interior environment would need to dry his wood to a moisture content of 8- 9% beforehand and then 90008 keep it that dry 90009 during the construction process . 90010 90006 The best way to do this is to use an accurate moisture meter.90010 90002 Moisture Content of Wood from a Flooring Installer’s Perspective 90003 90006 The National Wood Flooring Association (NWFA) has specific installation guidelines for wood flooring and how they relate to moisture content. 90010 90006 When determining the acceptable moisture levels in wood flooring before installation, the NWFA states that the flooring professional should establish a baseline for acclimation. Acclimation is the process for conditioning the moisture content of wood flooring to the environment where it will be installed.90010 90006 To establish a baseline for wood flooring acclimation, the installer will need to calculate the optimal moisture level of the wood by dividing the region’s high season and low season EMC. For example, if the expected EMC ranges from a low of 6% to a high of 9%, the baseline moisture content of the wood would be 7.5%. 90010 90006 The installer should then check the moisture content of multiple boards and average the results. A high reading in one area indicates a problem that must be corrected.90010 90006 We really can not overstress the importance of taking plenty of moisture readings. When you do this, you not only ensure that the entire batch is okay on average, but you’re also far likelier to catch boards that are statistical outliers and could cause problems. 90010 90006 If the moisture content of the product is well outside the range of optimal MC, the wood flooring should not be accepted because it will lead to shrinkage, bowing, cupping, and other physical problems. 90010 90006 For example, if the moisture content of the delivered wood is 12% and the optimal MC is 6%, then physical problems will occur during the acclimation process.90010 90006 90230 To avoid this problem, wood flooring should never be stored where environmental conditions are uncontrolled, such as garages and exterior patios. 90010 90006 As a general rule, with geographic exceptions, wood flooring performs best when the interior environment is controlled to stay within an RH range of 30% to 50% and a temperature range of 60 to 80 degrees Fahrenheit. However, the ideal humidity range in some climates may be higher or lower. For example, from 25% to 45% or from 45% to 65%.90010 90006 The National Wood Flooring Association (NWFA) has a chart that indicates the moisture content of wood at any given combination of temperature and humidity. The EMC in the recommended temperature / humidity range coincides with the 6% to 9% range used by most flooring manufacturers during the manufacturing and shipping process. Although some movement can be expected between 6% and 9%, wood flooring can shrink or swell more dramatically outside this range. 90010 90006 Installers should also measure the moisture in wood subfloors and concrete slabs as they can also affect wood flooring.The maximum subfloor moisture level for solid strip flooring or wide-width solid flooring is either 12% or 13%, depending on the manufacturer. 90010 90006 The National Association of Home Builders ‘Green Home Building Guidelines for solid strip flooring and wide-width flooring are as follows: 90010 90019 90020 For solid strip flooring (less than 3 «wide) there should be no more than a 4% difference in moisture content between properly acclimated wood flooring and subflooring materials. 90021 90020 For wide-width solid flooring (3 «or wider), there should be no more than a 2% difference in moisture content between properly acclimated wood flooring and subflooring materials.90021 90024 90002 Moisture Content of Wood and Lumber from a Builder’s Perspective 90003 90006 For most areas of the United States, acceptable moisture levels of wood and lumber can be in the range of 9% to 14% for exterior wood or for building envelope components within constructed assemblies. An MC in this range, therefore, is considered sufficiently dry for exterior in-service wood. 90010 90006 Using wood with a moisture content above 14% is not recommended because it may have detrimental long-term effects on the construction.90010 90006 In fact, according to M. Steven Doggett, Ph.D. LEED AP, the founder of Built Environments, Inc., wood moisture content as high as 15% can cause corrosion of metal fasteners and at 16% may lead to fungal growth. 90010 90006 When it comes to the moisture content of plywood or dimensional lumber, an MC of 17% to 19% reduces the overall strength of plywood, and an MC of 20% or more reduces the strength of dimensional lumber (ie, lumber cut to certain predefined sizes, such as 2x4s).90010 90006 A study by Imamura and Kiguchi (1999) showed that wood moisture content in excess of 20% can cause a 5% loss of nail shank diameter in four years and a projected 25% loss in 30 years. The same study showed a 40% loss in joint strength and concluded that a 20% MC may significantly compromise shear resistance of exterior walls. 90010 90006 When exposed to a constant RH, the moisture content of wood or lumber will come to equilibrium with its environment, resulting in an EMC for that species of a wood-based composite.90010 90006 The EMC of wood or lumber exposed to an outdoor atmosphere varies across the U.S. For instance, in the coastal city of Seattle, the EMC of wood or lumber is higher than the EMC of cities inland or in the Southwest. 90010 90006 Seattle’s EMC ranges from 12.2% to 16.5%. In the Midwest, the EMC of wood or lumber in Des Moines, Iowa, ranges from 12.4% to 14.9%. 90010 90006 In contrast, Las Vegas in the drier Southwest has much lower EMC percentages than most other U.S. cities. The Las Vegas EMC of wood or lumber ranges from 4.0% to 8.5%. 90010 90002 Acceptable Moisture Levels for Wood In a Nutshell 90003 90006 Based on common guidelines or recommendations, the acceptable moisture levels for wood are as follows: 90010 90019 90020 Wood objects used indoors: 6-8% 90021 90020 Wood flooring: 6-9% 90021 90020 Construction: 9-14% 90021 90024 90006 Keep in mind that a wood’s acceptable moisture level will depend primarily on 90008 how 90009 it will be finally used and the average RH 90008 where 90009 it will be finally used.However, the wood species and the thickness or size of the wood may also factor in. 90010 90006 In all cases, determining the acceptable moisture level of wood requires the use of an extremely accurate moisture meter. 90010 90006 Failure to allow the wood to acclimate or come into balance with the RH at its end-use location could result in any number of moisture-related problems after the wood product is constructed. These include warping, cracking, buckling, diminished wood strength, corrosion of fasteners, and even fungal growth.90010 90288 90006 Larry Loffer is a senior technician at Wagner Meters, where he has over 30 years of experience in wood moisture measurement. With a degree in Computer Systems, Larry is involved in both hardware and software development of wood moisture measurement solutions. 90010 .90000 90001 Moisture and Wood 90002 90003 90004 About Moisture and Wood 90005 90006 The durability of wood is often a function of water, but that does not mean wood can never get wet. Quite the contrary, wood and water usually live happily together. Wood is a 90007 hygroscopic 90008 material, which means it naturally takes on and give off water to balance out with its surrounding environment. Wood can safely absorb large quantities of water before reaching moisture content levels that will be inviting for decay fungi.90009 90006 90007 Moisture content (MC) 90008 is a measure of how much water is in a piece of wood relative to the wood itself. MC is expressed as a percentage and is calculated by dividing the weight of the water in the wood by the weight of that wood if it were oven dry. For example, 200% MC means a piece of wood has twice as much of its weight due to water than to wood. Two important MC numbers to remember are 90007 19% 90008 and 90007 28% 90008.We tend to call a piece of wood dry if it is at 19% or less moisture content. Fiber saturation averages around 28%. 90009 90006 90007 Fiber saturation 90008 is an important benchmark for both shrinkage and for decay. The fibers of wood (the cells that run the length of the tree) are shaped like tapered drinking straws. When fibers absorb water, it first is held in the cell walls themselves. When the cell walls are full, any additional water absorbed by the wood will now go to fill up the cavities of these tubular cells.Fiber saturation is the level of moisture content where the cell walls are holding as much water as they can. Water held in the cell walls is called 90007 bound 90008 water, while water in the cell cavities is called 90007 free 90008 water. As the name implies, the free water is relatively accessible, and an accessible source of water is one necessity for decay fungi to start growing. Therefore, decay can generally only get started if the moisture content of the wood is above fiber saturation.The fiber saturation point is also the limit for wood shrinkage. Wood shrinks or swells as its moisture content changes, but only when water is taken up or given off from the cell walls. Any change in water content in the cell cavity will have no effect on the dimension of the wood. Therefore, wood only shrinks and swells when it changes moisture content below the point of fiber saturation. 90009 90006 Like other hygroscopic materials, wood placed in an environment with stable temperature and relative humidity will eventually reach a moisture content that yields no vapor pressure difference between the wood and the surrounding air.In other words, its moisture content will stabilize at a point called the 90007 equilibrium moisture content (EMC) 90008. Wood used indoors will eventually stabilize at 8-14% moisture content; outdoors at 12-18%. Hygroscopicity is not necessarily a bad thing — this allows wood to function as a natural humidity controller in our homes. When the indoor air is very dry, wood will release moisture. When the indoor air is too humid, wood will absorb moisture.90009 90006 Wood shrinks / swells when it loses / gains moisture below its fiber saturation point. This natural behaviour of wood is responsible for some of the problems sometimes encountered when wood dries. For example, special cracks called 90007 checks 90008 can result from stresses induced in a piece of wood that is drying. As the piece dries, it develops a moisture gradient across its section (dry on the outside, wet on the inside). The dry outer shell wants to shrink as it dries below fiber saturation, however, the wetter core constrains the shell.This can cause checks to form on the surface. The shell is now set in its dimension, although the core is still drying and will in turn want to shrink. But the fixed shell constrains the core and checks can thus form in the core. Another problem associated with drying is 90007 warp 90008. A piece of wood can deviate from its expected shape as it dries due to the fact that wood shrinks different amounts in different directions. It shrinks the most in the direction tangential to the rings, about half as much in the direction perpendicular to the rings, and hardly at all along the length of the tree.Where in the log a piece was cut will be a factor in how it changes shape as it shrinks. One advantage of using 90007 dry lumber 90008 is that most of the shrinkage has been achieved prior to purchase. Dry lumber is lumber with a moisture content no greater than 19%; wood does most of its shrinking as it drops from 28-19%. Dry lumber will have already shown its drying defects, if any. It will also lead to less surprises in a finished building, as the product will stay more or less at the dimension it was upon installation.Dry lumber will be stamped with the letters 90007 S-DRY 90008 (for surfaced dry) or 90007 KD 90008 (for kiln dry). 90009 90006 Another way to avoid shrinkage and warp is to use 90007 composite 90008 wood products, also called 90007 engineered 90008 wood products. These are the products that are assembled from smaller pieces of wood glued together — for example, plywood, OSB, finger-jointed studs and I-joists. Composite products have a mix of log orientations within a single piece, so one part constrains the movement of another.For example, plywood achieves this crossbanding form of self-constraint. In other products, movements are limited to very small areas and tend to average out in the whole piece, as with finger-jointed studs. 90009 90048 90049.90000 Finally, the Truth about Wood Finishes 90001 90002 90003 It was sometime in the late 1970s when Bob Flexner opened his furniture making and restoration shop. Just like any other artisan, he felt immense satisfaction and a deep sense of pride and accomplishment in crafting and restoring furniture; naturally, he became quite good at it. 90004 90002 When it came to wood finishing, however, that was a different story. Flexner admits he struggled with finishing for years.A struggle not unlike what many other woodworkers also faced then and still face today. 90004 90002 What Flexner discovered was that much of the available information on finishing was contradictory and misleading. He realized this was why he and other woodworkers found finishing so hard to master. 90004 90002 This contradictory information came from a number of sources, including the only magazine dedicated to woodworking back then, Fine Woodworking, paint store clerks, finish product reps, and even the instructions written by the manufacturers of finishing products.90004 90002 Why so much misinformation? 90004 90002 Flexner says the answer is simple. It’s the difference between «physics» and «chemistry.» 90004 90002 90016 He explains that «woodworking is physics. A manufacturer could try to sell a band saw as a table saw because it has a table on it. But they can not get away with that because everybody knows what a band saw is and what a table saw is, and you can see it. » 90004 90002 «But a can of finish, that’s chemistry. And you can not see what the chemistry is.So a manufacturer can sell you a can of teak oil when it really is not teak oil. It may only be regular varnish thinned with paint thinner or just regular mineral oil. Yet they call it teak oil. You do not know. » 90004 90002 As a result, Flexner says this lack of visual confirmation enabled mythologies about finishing to develop that were spread from person to person, or «expert» to «expert.» 90004 90002 Flexner knows this all too well. After years of struggling with wood finishing, he began researching the subject at a major university library.There he studied at length the chemistry and technology of all coatings — paints, stains, and finishes. 90004 90002 Eventually, he learned to define the various types of finishes and their respective qualities, as well as identify what a finish product really was versus what the manufacturer claimed it to be. In short, he learned to separate the contradictory information, misleading labeling, and even deliberate deception from what was fact. 90004 90002 Armed with this knowledge, he went on to become one of the world’s leading authorities on wood finishing.His book, 90027 Understanding Wood Finishing 90028, has sold 400,000 copies since being published in 1994. Other books such as 90027 Flexner on Finishing 90028 and 90027 Wood Finishing 101 90028, plus hundreds of magazine articles, followed. 90004 90034 Wood Finishing Basics 90035 90002 To help woodworkers better understand wood finishes and some of the issues surrounding their applications, Flexner commented on some of the wood finishing basics. 90004 90002 He defines the term «finish» as a clear, transparent coating that’s applied in liquid form to wood by brushing, spraying, or wiping it on with a cloth.Sometimes, though, «finish» can mean an entire series of coats — meaning stain, one or more coats of clear finish, and maybe some coloring steps in between these coats. 90004 90002 A finish benefits wood in two basic ways: protection and decoration. 90004 90002 Protection means protection from moisture, either in a liquid or vapor form (humidity), or protection from scratches, dirt, and wear. The thicker the finish, the more moisture-resistant it is. 90004 90002 For example, three coats are more protective than one or two.Some finishes, however, offer no significant thickness or protection. That’s the case with wax, boiled linseed oil, and 100% tung oil. Each dries soft and gummy, so all the excess has to be wiped off after each application to maintain a workable surface. Doing this, however, provides insufficient thickness or protection. 90004 90002 Decoration means the finish showcases the wood’s natural beauty, color, figure patterns, grain, and depth. It also enhances the wood’s appearance by hiding defects.90004 90002 There are several types of wood finishes. Here are the basic ones most woodworkers use: 90004 90050 90051 Oil (100% tung oil, boiled linseed oil, and blends of these oils and varnish) 90052 90051 Oil-based varnish (including alkyd, polyurethane, spar, wiping and gel varnish) 90052 90051 Water-based finish (a finish that thins and cleans up with water) 90052 90051 Shellac 90052 90051 Lacquer 90052 90061 90002 Paint, too, is a wood finish, but one with enough pigment to hide the wood.Stain is also a wood finish, but one with pigment or dye plus a lot of thinner to make it easy to wipe off. What’s left simply colors the wood rather than hiding it like paint. 90004 90002 90065 Deciding which finish to use on a piece of wood depends on several factors. For instance, a woodworker might want to select a particular finish over the others if it offers greater durability, is easier to use, provides either a certain color or no color, dries faster, or emits the least amount of toxic fumes.90004 90002 90068 Durability 90069 is the strength of the finish film itself to resist being damaged. For example, polyurethane, initially introduced in the 1960s as a no-wax floor finish, would be a good durable finish. 90004 90002 Since a polyurethane finish dries slowly, it can be brushed on. Alternatives for someone wanting to spray on a durable finish would be to use a pre-catalyzed or catalyzed lacquer or conversion varnish. These are all called catalyzed finishes and are a little bit different than lacquer.Although they have different resins in them, they dry fast like lacquer and are just as durable or even more so than polyurethane. 90004 90002 If 90068 ease of use 90069 is important, then a simple wipe-on finish like Danish oil or an oil varnish blend can be used. A wipe on and wipe off product is much easier to use than working with a brush or a spray gun. 90004 90002 90068 Color 90069 is another consideration when choosing a finish. Water-based finishes, which are acrylics, give the wood no color nor do they darken as they age.They work well on lighter woods such as maple, birch or pine. 90004 90002 If finishing a darker wood, such as walnut, mahogany or cherry, then one of the other finishes such as shellac or lacquer is better. They give the wood somewhat of a yellowish to yellow-orange coloring. They also make the wood look richer and continue to darken as they age. 90004 90002 If 90068 drying time 90069 is important, shellac and lacquer finishes dry the fastest followed by water-based finishes. Varnish and oil take longer to dry, usually overnight in a warm room.90004 90002 Since lacquer dries the fastest, it works great when applied by a spray gun. Shellac and water-based finishes dry fast too, and can be either sprayed or brushed on. 90004 90002 90068 Less toxicity 90069 can be another factor in selecting a finish. One of the most toxic finishes is lacquer. It requires good ventilation. Some woodworkers find oil-based varnish thinned with paint thinner to be objectionable, but it’s not especially toxic. 90004 90002 The least toxic finishes are boiled linseed oil and 100% tung oil.They’re followed by water-based finishes and shellac. 90004 90034 Before the Wood Finish Goes On … 90035 90002 As already stated, one of the benefits of applying a wood finish is its protection against moisture and humidity. However, problems could occur if the wood object is not properly dried before adding a finish. 90004 90002 Flexner says, «You want the wood to attain its equilibrium moisture content (EMC) with the surrounding atmosphere so that it does not shrink and swell. You might notice sometimes a cabinet door with a frame around the outside and a panel on the inside after the whole door has been finished or painted.If the wood was not dry enough for that atmosphere, over time the panel shrinks and you have a line on each side where there’s no finish or paint. » 90004 90002 «So it’s important that you check and use a moisture meter, and that you check the wood for its moisture content (MC). You can use the EMC tables that will tell you what the MC should be for that atmosphere. Usually around 6 to 8%. » 90004 90002 90068 TIP 90069: 90027 Woodworkers can now easily calculate EMC (and troubleshoot wood moisture problems) using the free Wagner Wood h30 app.There are no complicated on-screen tables or computing — just a quick and simple calculation of necessary temperature and relative humidity for EMC. To download the app, click here. 90028 90004 90002 90110 An excellent illustration of this concern for moisture before applying a protective coat is seen in the construction of bowling pins. Bowling pins are made of hard maple because of its great strength and distinctive sound when the pins crash. During the manufacturing process, several pieces of the maple are glued together.However, if the maple pieces are not dried to the proper MC, the glued joints would fail and they would fall apart. 90004 90002 QubicaAMF Purchasing Manager Chet Moore explains how his company addresses this issue. «Essentially, we glue several pieces of maple together, so they have to be dry enough to be glued. But we do not dry it quite as low as a furniture maker. We try to keep it at a certain moisture level to optimize the production process and the quality of the pin. But if the correct moisture level is not attained, the glued pieces will not stay together.That joint will eventually fail, «he says. 90004 90002 To prevent this from happening, QubicaAMF uses a Wagner wood moisture meter throughout the kiln drying process. The Wagner meter, highly acclaimed for its accuracy, comes with a special attachment that the kiln operator can slide into the center of the wood bundles before they are placed in the onsite drying kilns. 90004 90002 This enables the kiln operator to check the different layers in the bundles as they’re drying. Since the Wagner meter is pinless, it leaves no holes in the maple.90004 90002 Once the wood is dried to the ideal MC level, they can glue the pieces and then coat it with a plastic called Surlyn®. This coating protects the maple from damage and keeps out any unwanted moisture, thereby extending pin life. 90004 90034 Applying a Finish 90035 90002 After an object is made and it’s time to apply a finish, Flexner says the MC of the wood becomes less of an issue; that is, unless the MC is so high (almost wet to the touch) that it causes a problem with the finish.90004 90002 The thicker the finish that’s applied, the better it’s going to resist moisture or humidity exchange, but Flexner cautions woodworkers about applying a finish that’s too thick — typically, more than three coats. What happens is that the finish deteriorates and cracks faster. 90004 90002 The exception would be a poured-on epoxy finish — like what some restaurants use on their dining tables. The boards in these tables show no visible shrinkage or expansion because the epoxy finish is so thick that it just stops the change almost entirely.But, of course, epoxy is not a very functional finish for a cabinet or some fine pieces of furniture. 90004 90002 While a regular finish can greatly minimize the shrinkage and expansion of wood, the wood will still undergo some movement. This often occurs during the change of seasons or if a piece of furniture is moved from a very dry location, like Phoenix, to a much more humid locale, like Miami, or vice versa. 90004 90002 For example, in winter and summer, when the air is drier due to a heater or air conditioner running, the wood shrinks.In the fall and spring, when HVAC units may not be on or when windows are left open, the wood can expand but again, not to the extent that it normally would if there were no finish on the wood. 90004 90002 Flexner also notes that the first coat of any finish seals the wood. In effect, the finish stops up the pores in the wood so that the next coat of finish, or any other liquid for that matter, does not penetrate easily. 90004 90002 90135 This first application of finish raises the wood’s grain so that it feels rough.Rubbing sandpaper lightly over the rough surface will make it feel smooth. 90004 90002 Nothing else needs to be done to the wood unless, after this first coat, one of two issues need to be addressed. 90004 90002 The first issue involves the use of alkyd varnish and lacquer. They gum up sandpaper when the wood is sanded, so a sanding sealer will be needed. Flexner notes that sanding sealers weaken the finish and should be used only when finishing a large project or doing production work. 90004 90002 The second issue may involve problems in the wood such as resinous knots in softwoods.This problem can be corrected by using shellac for the first coat. 90004 90034 Closing Comments 90035 90002 Obviously, this article only skims the surface of all there is to know about wood finishing. For anyone wanting a more in-depth coverage of finishing, read Flexner’s book 90027 Understanding Wood Finishing 90028. 90004 90002 For the amateur woodworker or someone wanting to do basic finishing, Flexner’s book 90027 Wood Finishing 101 90028 would be ideal. It’s not as comprehensive as 90027 Understanding Wood Finishing 90028, but it comes with plenty of photos and step-by-step illustrations.90004 90155 90002 Larry Loffer is a senior technician at Wagner Meters, where he has over 30 years of experience in wood moisture measurement. With a degree in Computer Systems, Larry is involved in both hardware and software development of wood moisture measurement solutions. 90004 .