Deck board installation bark side down

Some information contained in it may be outdated. In truth, the answer is very simple. Lay deck boards so that the best-looking face is facing up! Wood shrinks and swells twice as much in the direction parallel to the growth rings as it does perpendicular to the growth rings. The combined effect of these different rates of movement causes lumber to deform.

Flat-sawn lumber, lumber that is cut so its wide face is parallel to the growth rings, cups as it gains or loses moisture. A good way to visualize the typical distortion is to imagine that the growth rings straighten as wood dries. Therefore, a wet piece of lumber installed with the bark-side up, will cup to hold water on its surface as the board dries. However, kiln-dried lumber is usually surfaced imparting a true rectangular shape after the lumber has been dried.

A dry piece of lumber installed bark-side-up will cup to shed water from its surface as it gains moisture — because if the growth rings straighten out as wood dries they will curve as the wood becomes wet. So, the original moisture content of a piece of lumber when it is installed — and — the conditions to which it will be exposed after installation control a boards final shape.

Heartwood is often more resistant to decay than sapwood of the same species. Clearly you would install lumber bark-side down to expose the more resistant heartwood region to the elements. But not so fast. Heartwood is difficult to impregnate with wood-preserving chemicals.

These differences in shrinkage may be accounted for by the presence of ray cells in the wood Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Note: appearance of your Comment below may be delayed: if your comment contains an image, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay. Just ask us! Search the InspectApedia website. Comment Form is loading comments Free water on or in wood dries quickly but bound water within wood cells takes much longer to dry or requires kiln drying or other measures for its removal.

Picture the clothes in your clothes washer at the end of a spin cycle. The wet clothing has been squeezed until you couldn't get more water out of it - that clothing is at its fiber saturation point. And just as FSP varies among wood species, if you've ever done laundry you've noticed that some fabrics retain less water at the end of the washer's spin cycle than others. The moisture transport coefficient used in this model is the effective water conductivity.

It is a function of moisture content, temperature, and direction of flow. The results show that the effective water conductivity increases exponentially with moisture content and temperature. The effect of temperature cannot be solely explained by the variation of the viscosity of water.

The variation of the moisture content-water potential relationship with temperature would explain a large part of this effect. The flux-gradient relationship obtained at given moisture contents were found to be linear, confirming the validity of the model for the experimental conditions considered in the present work.

Abstract: This is a study on the shrinkage of wood representing the wide range of morphology variation in leaning trees. The more heart cut and edge grain lumber you can select when picking boards, the better.

The main reason proponents like this method is, ironically, to reduce cupping. But when it rains, and the board warps, water collects in the concave shape and pools there.

Wood develops a memory over time, and that's why you see deck boards in the permanently cupped position even when they are dry when installed bark side up. Another reason this method may be used is to avoid a defect called shelling.

Shelling is more likely to occur with the bark side down method. This is more common in Douglas fir and Southern pine lumber than with many other deck woods.

But in general, you can largely avoid this problem by being more selective when choosing each piece of lumber. It's also important to note that the bark side up method was popularized when heavy green-treated lumber was used for deck boards, and that lumber was unevenly saturated, causing warping problems.

Today's quality lumber is kiln-dried before it is cut, minimizing uneven drying. This creates a crowning warp when wet. As a result, water is shed from the board, as opposed to pooling on it. Also, the exposed board face is heartwood closer to the tree's center versus sapwood, and heartwood is more decay-resistant.

Bark side down is also the preferred method because it minimizes the chances of trip hazards due to cupping. Actively scan device characteristics for identification. Use precise geolocation data.