Yellow substance on floor joists - sap, glue, or something worse?

[Ken JDA]

I'm a new homeowner, and for the first time ever I was looking at the floor joists and subflooring from a new angle and I noticed something strange.

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These small, yellow, translucent, spherical little 'jewels'. This area is on subflooring very near our blower unit so my mind immediately went to mold. The area always seems dry to me, but I have no idea what happened here with previous homeowners nor do I really know what dry 'is' (how dry is dry enough if the surface gets very cool from being near blower ductwork?). These two photos are taken of the same area but different flashlight angles to show how they glimmer and refract light.

Anyways I took lots of pictures and scraped a small area of them and found them to be dry.

They glimmer in flashlight light because they do indeed reflect/refract light. The broken off pieces also appear like little yellow jewels. They are translucent and very yellow.

I did a little research and it seems to me these are probably sap extruded from the lumber. However, I find it concerning that I don't notice any of this on the few other joists I can see that are not near the blower unit (2 joints over in either direction).

This photo, taken where you can see the main girder, and right next to the blower, has the most of the substance. It appears the substance is on two different kinds of wood (I am not good at identifying wood). Which makes me think it might be sprayed glue???
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Finally, here is the substance on a tissue. It easy scrapes off, it falls like dust. It still appears translucent and very yellow (again kind of looking like some kind of artificial substance, like glue?)
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Is extruded dry sap something to be worried about on floor joists?
Could they instead be some sprayed glue?
Are they possibly not sap, is there any mold that is translucent?


Thank you for any ideas / help!

[Pierre Coulombe]

Ken, Although harvested softwoods used for construction may be listed as kind-dried, there still is some level of moisture still in the wood. The moisture varies due to a number of factors for the wood (where harvested, time in the kiln, density of the wood, seasonal growth, relative humidity, age of the tree where the wood was harvests, and on forth....) Matter of fact, wood will absorb and release moisture over its entire lifetime/existence. Those "jewels" are in fact sap that weeps from the wood over its lifetime, more so when it is fresh as the wood dries in place. You can go to the big box lumber yards and see their stock of building lumber with the markers on them as well. No need to be overly concerned about them.

[Gary Burnett]

Sub flooring looks OK. I want to know if those are termite mud caps at the floor joist in the second picture. Looks like spots where termites have popped out and then capped the hole. Can't tell if it is mud or dirty spider webs.
If it's termites my answer to your question would be "something worse"

[Ken JDA]

Ken, Although harvested softwoods used for construction may be listed as kind-dried, there still is some level of moisture still in the wood. The moisture varies due to a number of factors for the wood (where harvested, time in the kiln, density of the wood, seasonal growth, relative humidity, age of the tree where the wood was harvests, and on forth....) Matter of fact, wood will absorb and release moisture over its entire lifetime/existence. Those "jewels" are in fact sap that weeps from the wood over its lifetime, more so when it is fresh as the wood dries in place. You can go to the big box lumber yards and see their stock of building lumber with the markers on them as well. No need to be overly concerned about them.

Thank you for all this info. Very interesting information, I really didn't know that much about how wood behaved long after it is cut! Appreciate the info!


Sub flooring looks OK. I want to know if those are termite mud caps at the floor joist in the second picture. Looks like spots where termites have popped out and then capped the hole. Can't tell if it is mud or dirty spider webs.
If it's termites my answer to your question would be "something worse"

Are you talking about the dark grey bits? Those are dirty spider webs. I looked up stuff on termites in response and saw mud tubes online. There's nothing that looks like that. But this is precisely the kind of info I want to know what to look out for. I don't want to stick my head in the sand on anything. Also it sounds like I should clear up our crawl space a bit, as it could attract termites to have a little loose wood in there.