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I received my terrace decking boards today. Almost all of them have fairly deep cracks on the ends and some have cracks on the face.

Should these be considered as critical damages or I should still be able to use them in my construction? The wood is Siberian larch, so very resistant to rot.

Should I expect them to get deeper with time?

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  • The beaded surface treatment is interesting and unlike any I've ever seen for decking. It's a nice visual enhancement, and I can see the possibility of it increasing traction, especially when the board is wet. However, any time it rains, water will sit in those grooves and not drain out as well, especially if the deck slopes across the width, not along the length of the decking. Water sitting there will increase the rate at which the boards rot out, even if they're fairly rot resistant. – FreeMan Apr 1 at 16:31
  • That is so called French contour. The slope is planned across the decking length, so should be ok. – Dmytro Prylipko Apr 3 at 7:59
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That's called "checking", and it's what happens when wood dries out. Always. It's why wood used for exterior purposes should be sealed fairly readily. It's not usually a structural concern as it's parallel to the grain and the strength axis.

You'll want to cull (trim away) any wood that you don't consider aesthetically appealing, do your installation, and then promptly seal the wood.

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  • Think he might be concerned more about the cracks on the finish surface. Second to last picture is crack right down centre of board, thought it was a seam at first. – crip659 Mar 31 at 19:56
  • I thought I addressed that in my second paragraph. It's solely a matter of appearance and personal standards. – isherwood Mar 31 at 20:06
  • I am rather worried whether this compromise the structural integrity of the boards. Visual appearance is less important, if it can be fixed with some putty or so. – Dmytro Prylipko Mar 31 at 20:26
  • Take a look at any log cabin photo. You'll see huge checks that don't matter. It's not a problem. – isherwood Mar 31 at 20:47
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    Log cabin construction is an improper example for saying checks are not a strength problem. First, most of the logs lay on top of each other, so they are not spanning anything. Second, when they do span something, like a header, they are grossly oversized. – Lee Sam Mar 31 at 22:04
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Of course the splits (“checks”) will affect the performance AND strength of the wood.

Wood is a product of nature, it’s not manufactured so there will be imperfections in the wood. Wood shrinks more “across” the grain rather than than the length of the grain. So you are seeing the checks developing in each piece of wood.

Your wood is to be used for deck boards, so the material will remain outside AND will continue to shrink and split. It will not substantially affect the strength of the wood to the point that it will NEED to be replaced. However, it will become increasingly unsightly and the checks will get larger (longer and wider).

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