01 of 05
Types of Edge Grain in Deck Boards
The debate about whether deck boards should be placed "Bark Side Up" (growth rings curving down) or "Bark Side Down" (growth rings curving up) has raged for years.
Bottom Line: The hype that "bark side up" is always the answer is not accurate. This tutorial will explain why then you can decide which way you want to install new deck planks or replace a damaged wood deck board.
Wooden deck boards typically come in three cuts (cut a board with a circular or power mitre saw to get a clean view of edge grain):
- Heart - Center of the growth rings are in the center of the board edge and is not too common because these are dimensionally prime pieces of lumber
- Edge Grain
- Flat Grain
The issue of which way to orient the deck board is only relevant with Flat Grain boards because the orientation of their growth rings will affect how the wood reacts when wet. And in the case of a deck board, whether you have a "cup" warp or a "crown" warp.
Why Boards Warp
When deck boards get wet, they do not get wet consistently. That is, the wood exposed to the rain and the wood on the bottom of the board are not being exposed to the same moisture. As a result, the wood fibers on the weathered or exposure side expand more than the fibers on the bottom. That creates dimensional changes in the wood. Wood warps the opposite orientation of the growth rings. The orientation of growth rings and which side gets wetter determines the way the wood warps on your deck.Continue to 2 of 5 below.
02 of 05
Heart Cut and Edge Grain Boards
With heart cut and edge grain boards, the issue of warping is very small. The wood distorts much less significantly than flat grain cuts and the issue of "bark side" does not matter here. The more heart cut and edge grain lumber you can select when picking boards, the better.Continue to 3 of 5 below.
03 of 05
Bark Side Up
"Bark side up" is the conventional wisdom. The main reason proponents like this method is, ironically, to reduce cupping. But when it rain, 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 dry when installed bark side up.
Another reason this method may be used is to avoid a defect called "shelling." Shelling can occur with the bark side down method and is a raised grain defect where latewood growth separates from early wood growth and creates a flat splinter-like defect after repeated wetting/drying cycles. This is more common in Douglas Fir and Southern Pine lumber. But all you have to do is be more selective in your pieces of lumber selected to avoid this problem.
This method was also popularized when heavy green treated lumber was used for deck boards and that lumber was unevenly saturated causing warping problems.Continue to 4 of 5 below.
04 of 05
Bark Side Down
"Bark side down" has the deck board oriented, so the end grain growth rings curve upward. This creates a crowning warp when wet. As a result, water is shed from the board as opposed to pooling in it. Also, the exposed board face is heartwood versus sapwood and heartwood is more decay resistant.
One reason to be careful with this deck board orientation is to avoid a defect called "shelling" as mentioned in the previous section. Shelling is a raised grain defect where latewood growth separates from early wood growth and creates a flat splinter-like defect after repeated wetting /drying cycles and is more common in Douglas Fir and Southern Pine lumber. But be selective in the pieces of lumber you choose to avoid this problem.
This orientation of bark side down is our preferred method because it avoids the unsightly trip hazard of cupping.Continue to 5 of 5 below.
05 of 05
The debate still is on, but in the end, there are pros and cons for each method of deck board installation. But we find that avoiding a deck made up of cupped deck boards that look like ridges for traction when wet is generally the most important thing for homeowners.