When is dry rotted sapwood a concern?

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Forum topic by eddit posted 11-13-2018 03:13 PM 958 views 0 times favorited 4 replies Add to Favorites Watch
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16 posts in 1027 days

11-13-2018 03:13 PM

Topic tags/keywords: walnut sapwood lumber rot

I purchased some air-dried lumber from a local lumber guy, walnut slabs. I noticed that the sapwood on the edge (1 or so inches thick) was dry rotted. I can break off a bit by hand, with some force. I planed a bit of the heartwood and it looks great. In contrast, I’ve purchased kiln dried lumber from another local guy, and the sapwood seems to be just as strong as the heartwood. I see people incorporating walnut sapwood into their projects with beautiful results. 

Should I be concerned about dry rotted sapwood? Is this the difference between air-dried and kiln-dried? How safe is it to incorporate walnut sapwood into your projects?

4 replies so far

View EPJartisan's profile


1123 posts in 4287 days

#1 posted 11-13-2018 04:22 PM

Morning. Most of the time sapwood rots because it is the “living” part of the tree trunk, while the heart wood has died and compressed itself, which hardens the cells and encapsulates the stuff left in them for rot resistance. Not that all species of tree reacts the same way, silver maples can rot from the inside out for decades before falling down.

Klln dried = boards put in a large controlled heated oven to reduce the moisture content evenly. Kiln dried wood sometimes does not get its movement out of the fibers and can bend and twist while working it. BUT kiln dried wood “cures”, or hardens, the sapwood far better than air drying, making it less likely for the cells to absorb moisture again.

Air Drying = wood stacked in a (hopefully) semi-controlled warehouse divided by slats of wood to allow air to circulate around the boards. The wood may not dry evenly, but the movement is easier to work with. Sap wood in air drying is still subjected to mold and rot until fully sealed, because the cells more readily absorbs moisture from the air.

The contrast between sap and heart in walnut is one of those special moments. You can harden sap wood with a wood hardener from mini-wax, it takes more soaking coats and the hardener make it more difficult to cut and shape after. If you have stable sap wood it can be used most anyplace for decoration, but will never have the strength of the heartwood. Avoid sap wood for joinery and structural parts. My morning two bits.

-- " 'Truth' is like a beautiful flower, unique to each plant and to the season it blossoms ... 'Fact' is the root and leaf, allowing the plant grow and bloom again."

View eddit's profile


16 posts in 1027 days

#2 posted 11-13-2018 04:52 PM

Thanks EPJartisan, you answered this perfectly.

View a1Jim's profile


118163 posts in 4739 days

#3 posted 11-13-2018 06:30 PM

In years gone by a master furniture maker named Franklin H. Gottshall use to get walnut logs and store them outside until the sap wood rotted away then he would mill the logs and build beautiful furniture from the wood. This was when sapwood was considered a defect ..


View WDHLT15's profile


1819 posts in 3638 days

#4 posted 11-14-2018 12:08 PM

The difference between the two sources of walnut was that the first that had the rotted sapwood was sawn from a log from a tree that had died and stood dead for a while, or from a log that was not sawn while the log was fresh and green. The log laid out long enough for the sapwood to begin rotting. The second source came from a fresh green log that was sawn promptly after felling so the sapwood was fresh and sound.

There is no difference between the strength of sapwood and heartwood in walnut. The sapwood contains the living cells that store sugar (parenchyma) and is the main water conducting conduit for getting water from the roots to the crown. All sapwood becomes heartwood at some point. The wood structure is the same, but the heartwood is where the tree dumps all kinds of stuff called extractives from the photosynthetic process as the tree ages. This leads to the color difference.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT40HD35 Sawmill. Nyle L53 Dehumidification Kiln.

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