Forum
« It's Time to Party!!! Cleaning service »
October 13, 2009
What kind of wood do we use
to sister termite-damaged joists in the basement?
The old, undamaged wood is to be treated for termites by an exterminator to prevent further damage. Some old repairs were made with the greenish pressure treated wood, which I understand emits harmful gases - so I don't want to put any more down there. So what do we use to sister the single joist that needs sistering now?
Comments
I'd stick with regular untreated joists. As long as the termites are treated the wood should be fine. As far as pressure treated wood goes, it may protect against the elements, but I don't believe it has any defense against termites, beatles, ants.
Posted by: isaacly at October 13, 2009 9:42 PM
I'd use an LVL (laminated veneer lumber). They are engineered to carry loads and are very stiff. You'd want to bolt it to the old joist.
http://www.gp.com/build/product.aspx?pid=1392
masterbuildernyc@gmail.com
Posted by: masterbuilder at October 14, 2009 7:51 AM
Depends on what you're sistering for and the bigger picture.
I replaced the plumbing wall end of a handful of joists and did quite a bit of sistering using 2x8s sandwiched and bolted together using 1/2" schedule 5 bolts. This worked because the damage was localized, there was plenty of parent material to sister to along the length of the joist, a lot of the work I was doing was creating a level surface along the length of otherwise structural joists and I was mostly working on the short side of the load-bearing beam--there wasn't much cantilever. My house is also on the narrow side.
LVL is good for things like creating arches where there were load-bearing walls and other engineering feats. Much joist work is not an engineering feat worthy of an expensive LVL beam because most joists are sitting about 16 inches away from another perfectly good joist--the load of the floor, walls, etc, is pretty well-distributed.
That said, there are a lot of times when that's not the case. If you are dealing with a particularly wide span, are replacing many joists entirely instead of sistering to an existing joist that's still mostly structurally solid, or are working to support a structurally problematic part of the house like the mortise-and-tenon floating in midair and filled with bricks in front of your fireplaces, or if you have any other reason to think that the regular old wood joists that you're replacing weren't good enough, then I would surely consider an LVL.
But honestly, having to do this kind of structural work on your house sucks, and the only upside is that at least the materials to fix it are cheap.
Posted by: vanburenproud at October 14, 2009 8:16 AM
thanks all - the joist that requires repair is the first short one that goes across in the very front of the house, right up against the masonry. (inconveniently, right where the gas, electric, and oil tank are). It's 18' long, and the last 4-5' are damaged.
Any ideas about how to attach the new wood to the old?
I know that the new wood should be bolted along the length of the repair, and should be more than the length of the damaged part (we're going to try to do 10' of new wood) but I can't get a bolt into the old joist because it is right up against the masonry, except for the 2' where the front hatch (and the worst of the damage) is.
Posted by: jellystew at October 14, 2009 11:05 AM
If there's truly a vast expanse of good wood to lag to on either end, you can use lots of 1/2" lag bolts.
There should be enough good wood on either side anyway. Otherwise, you should be thinking in terms of replacing the joist instead of sistering to it.
Posted by: vanburenproud at October 15, 2009 7:47 AM
Post a comment
Please be patient while your comment is published. It may take a moment.