Dry Rot Investigations

[CBSE]

I have a contractor asking me if I can do a dry rot investigation on a single story wood framed building. I've never done one nor seen one done. Who usually does these? Engineer or specialized group?

 

[JStructsteel]

If you have done any wood design/inspections before you should be able to look at a piece of wood and decide if its damaged to the point where its not serviceable for the structure anymore

Its a mold issue, so they should be included too, they can treat, remove the mold, you decided if its structurally sound anymore.

 

[msquared48]

Be careful here. Rot is not always visible. Sometimes you have to drill into or poke the member to see the internal condition.

Mike McCann, PE, SE (WA)

 

[CBSE]

Thanks.

So the basics are:

Drill 1/4 inch diameter holes to see what inside material looks like.
Determine if members are structurally sound


Any advice on what to look for? I did a quick internet search and it seams it is gray with white spider web/mold looking ares? I will do more research, but if you have a good technical paper you know of that would be great.

Thanks.

 

[racookpe1978]

Yes, you can do it. You're looking for "soft wood" first - that looks good on the outside but feels like tissue paper under the paint, then for moldy or darkened wood, termite or carpenter bee damage on the ends, then peeling off boards and unfastened boards and trim and siding.

HANDS ON INSPECTION! Wear coveralls or long-sleeves and be prepared to scramble around the building.

Get a medium length awl with a round or wood handle - it will cost 4-6 dollars. Not too big, but you must a have a modestly sharp point: 3-6 inches long is adequate. As you walk around simply "poke" the wood randomly and knock on it with your knuckle. The awl will penetrate any bad spots immediately, but leave a small dimple on good wood. Bring a ladder and check eaves, near downspouts, under the drain points, etc. Dry rot is unlikely in the big open spaces in the middle of an accessible dry area, but be suspicious of upper boards and lower boards. When you find a spot, keep checking nearby boards until you get to good solid wood.

Write your report with caution using something like, "To the best of our knowledge using non-invasive methods, we inspected the following accessible visible areas at address ... on __ September 2015 and found w x y z. ... Additional damage from dry rot and sub-surface decomposition such as interior termite damage may be present, but was not observed in the areas checked on this date. Continuous termite inspections and prevention by a qualified pest control service are always essential for any wood structure at all times in all environments. etc

 

[CBSE]

That's great insight! Thank you!

 

[Jerehmy]

Don't forget to check the crawlspace if the home has one. People like to leave the vents closed and wonder why they have moisture --> deterioration.

Tools:
- A sling psychrometer works great to see if there's a humidity issue causing the mold and subsequent rot as opposed to water infiltration.
- A moisture meter is also good so you can see the moisture content of the wood upon inspection.
- Buy a set of probes, they work great. I swear we have kodiak probes but I can't find them online anywhere..

Also, dry rot = brown rot (wood never rots when its dry).

 

[tstructural]

I saw a building with what they called 'excessive dry rot' and the wood was so black it appeared to be charred from fire. I don't know if the appearance varies based on the type of wood or maybe because this was exposure adjacent to salt water - I'm no expert.

The 'poking' of the wood is what the inspector did. He could tell how deep the damage was based on how far the probe went into the framing.

 

[Ron]

Agree with racooke1978 and msquared48....you can do it but be careful!

I would suggest that you visit the National Forest Products Laboratory website and review a few documents there. It is a treasure-trove of information and it's free. Excellent papers on wood rot.

Dry rot is somewhat of a misnomer. Most often, the rot is caused by some type of fungal or algal organism, exacerbated by moisture. When the moisture goes away, you are left with a wood microstructure that is compromised, flaky and does not support structural applications.

racooke's advice for wording is good, but I would make the following changes....

"To the best of our knowledge using non-invasive methods, we inspected [highlight #FCE94F]observed[/highlight] the following accessible visible areas at address ... on __ September 2015 and found w x y z. ... Additional damage from dry rot and sub-surface decomposition such as interior termite damage may be present, but was not observed in the areas checked on this date. Continuous termite inspections and prevention by a qualified pest control service are always essential for any wood structure at all times in all environments. etc

The term "inspection" carries a higher connotation than "observed". It implies that you did something "exhaustive" and that you checked "every possibility". That's not practicable, so just keep it to "observed".