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nezwick 10-09-2012 04:32 PM

Old powder post beetle damage to beam in basement - is it really a problem?
1500 sq. ft. 2-story house built between 1872-1877. Vertical plank construction, meaning no stud walls (interior or exterior).

I've slowly been working down in the basement, removing all the PO's garbage, nasty old insulation, doing wiring/plumbing, etc. The PO, who owned the house since 1955, had "boxed in" a large beam in the basement using 1/4" plywood, so as to conceal the beam. I decided to remove the plywood, only to discover there is extensive insect damage to the beam. The beam is basically a hand hewn log, approximately 8x8.

Forgive me if I use the incorrect terms here. The item in question used to be the rear "sill beam" which rested on the stone foundation before a small kitchen addition was tacked onto the back in the 1930s and the basement was later dug out beneath this addition (1950s).

The house's floor joists run parallel to this beam, so it is not carrying any floor load. It does, however, carry the weight of the 3 layers of 1-by planks that run from sill to eave on the back side of the house (gable end), and whatever weight the addition is imposing on the back wall of the house.

At one point, a triple 2x10 beam was added which runs underneath, and is perpendicular to, this damaged beam. This newer beam is supported at both ends by masonry structures and is VERY solid.

Now I guess my main question is, is the beam with insect damage really something I need to be concerned with? Nothing else seems to be failing/sagging due to the damage.

Here is a photo to show the extent of the damage. Yeah it's bad. It feels like touching a sponge, and I can stick a screw driver straight into it (the large hole was from old wiring which I removed).

And here is a rough and not-to-scale drawing of what I'm trying to describe above.

I know nobody can really say "for sure" and I know assessing structural issues is a sensitive topic, but I appreciate any input!

joecaption 10-09-2012 07:06 PM

That beam has to be replaced.
Once that's done I would also get any of the other exposted wood treated with Boric Acid.
Tim-Bor and Bora Care are two products I've used before.

nezwick 10-09-2012 07:29 PM

Thanks for replying. I had a pest inspection when I bought the house and the person said there were no infestations of any sort, though I do understand that he couldn't see this beam since the PO covered it up. The adjoining old sill beams are intact, as are the floor joists, floor boards, etc. What exactly would the boric acid solution do if there are no beetles in the wood and haven't been for 50 years?

As far as the beam replacement, I'll add that to the list of things needing done but it's obviously been like that for many years - and it only spans 8.5 feet before the load is picked up by that massive triple 2x10 set so I don't believe the house is going to collapse. Is this a logical train of thought?

joecaption 10-09-2012 07:53 PM

Not sure how you could be sure there's no insects in the wood.
Powder Post Beetle live deep in the wood and only come out once a year, They mate then bore there way back in. Unless you happen to be there watching the very few days they come out, of cut the wood in 1/2 your not going to see them.
Why would you want to take the chance of future damage if there still living in the other pieces of wood near that area?
Could be there all dead but for a just a few dollars I'd make 100% sure they were.
I've never once seen them just live in one single piece of wood where there's other pieces attached to it.

nezwick 10-09-2012 08:33 PM

Interesting, well I always assumed that if there were insects boring in the wood, that there would be dust on the floor or the beetles could be heard/seen.

I'm no exterminator, but I did examine the surrounding wood and found little or no powder post beetle holes like what can be seen in this particular timber. I also stabbed at the other beams with my screw driver and they were rock hard.

I'm going to look into the boric acid solution because it will bring piece of mind. I'm also going to email the PO to see if she has ever had the basement treated. She's 84 years old so she may not remember!

joecaption 10-09-2012 09:12 PM

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