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Question DetailsAsked on 11/9/2014

Am I able to repair a 2-3' section of rotted sill plate and rim joist, or should I hire a professional??

I found a completely rotted out section of sill plate and rim joist on the corner of the northwestern wall of my house. I believe it was caused by borer beetles. The damaged wood is on the wall running parallel to my floor joists. There is no interior damage noted; floor feels sound, no cracking etc. From the crawl space, all other wood appears/feels strong and sound. Only damage is the corner of the foundation, about a 2' section of sill (completely eaten away, save about a 1/2" along the 2" width and the rim joist in the same corner is soft enough that I can push my screwdriver into with ease. I am not a contractor, but I do feel comfortable around tools and building materials, and am a fast learner (I built a walk in closet for my son). Is this a job I could easily do on my own or is it something I should have a professional do?? We are in a tight financial position and would like it done right at the lowest cost possible.

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3 Answers


Here is a prior answer I gave on a very similar question -

The corner will be bearing more weight than other areas along the wall because it has roof load from both sides of the corner, so you are likely to need some support for the wall while replacing this piece of sill (assuming you mean bottom plate of the wall) - and certainly if replacing some rim joist.

I would say, unfortunately, you should get a Carpenter - Framing or General Contractor to be on the safe side, because without actually looking at it I can't say if you could safely do it yourself or not. If a built in closet is the limit of your framing experience, as opposed to building a house or relevelling a pier-supported house, I would say this is probably beyond what you want to tackle - unless you want to try out just how friendly your homeowners insurance company is.

For instance, you say it is on a wall running parallel to your floor joists - but if you have a house that was built funny or is small, or have a hip or flat or mansard roof, that could be a roof joist/rafter load bearing wall. Either way, it has the weight of the wall and siding and at least a small piece of the roof (including all overhang on that end), so it is not truly "non-load bearing" in a functional sense - it will have at least a good few hundred pounds per running foot on it.

You also did not say if you have say a single or doubled joist or Tee-joist on the foundation, or a built-up flooring system with rim joist all around, or engineered joist or what along there - and until you get into taking it out you will not know how much other support needs to be replaced, so safer to go with a pro. It is quite possible, from your description if I read it right, that you need to replace a section of sill plate - not a hard thing to do - but also a piece of rim joist in probably a built-up flooring joist system which was built up flat with plywood decking, then the walls built on top of that - standard construction today and for some decades. Therefore, you will actually be taking out the wall bottom plate, some plywood decking (floor sheathing) and rim joist - and the latter cannot generally just be replaced in end-butted pieces, it will have to be spliced into the remaining portion with an overlapping piece of joist, plus it has to be fastened to the plywood and to the foundation also. For instance, if replacing the end 3 feet of it, you will probably have to replace that plus splice in a sistered 6 foot piece of joist inside of it (inside the flooring unit), bolting or nailing (depending on design and code requirements) them together at fairly close fastener spacing. This means you are disassembling the corner of the floor support system, possibly not only on that side of the flooring assembly but maybe wrapping aroundcthe corner a bid to get all the rot/decay. Hence, best to get a full general contractor with experience in repairing damaged framing, as he can also handle the siding removal and replacement, any piping or electrical he runs into, and repairing flooring and drywall and paint, trim, etc that ends up coming out - because he is certainly going to have to get in underneath the flooring system from the basement or crawlspace ceiling, from the outside, and maybe from inside the first floor corner room as well - possibly at the flooring level to replace some flooring sheathing, and maybe into the bottom of the wall too depending, though that part you can usually do from outside.

Really hard to guesstimate cost, but assuming it does not go more than about 3-4 feet from the corner, you are probably talking $500 bare bones if replaceable without jacking or plywood replace to probably more likely $1000 range if it goes easy and fast and the plywood is OK, to $1000-2000 probably if a bit more work and into some plywood sheathing replacement but still not extensive invasion by the borers so limit tothe few feet in the corner of that floor - and no significant borer invasion distance into adjacent side of house or up into the walls. OF course, if is rot or insects and it/they ran amuck and you just don't see it yet, all bets are off, but that is pretty rare.

One other thing - if the rim joist can be penetrated with a screwdriver it is either heavily wormed or rotten - so I would peel a piece out and see if rotted or if insect holes or bodies/body casings in there, because in that case you are probably looking at water damage (and maybe or maybe not borers also, depending on if you found definitive proof of them) - so possibly a siding or pipe leak, and likely needing exterminator services once opened and fixed but before closed back up too. From your description of the corner being completely rotted out, I would guess the water damage occurred first from a leak (which means it might trackup the corner of the house aways), then the insects came BECAUSE the wood was wet and rotting. It is really fairly rare (except with flying termites) for insects to invade intact wood - usually they prefer nice moist, slightly rotting wood before they move in.

Answered 5 years ago by LCD


Thank you for your very thorough answer! I will definitely be calling in a pro, since you lost me after rim joist.

I do believe it started as water damage. It is on the far corner of our house where there is a downspout that got blown of in several of the last few hurricane's that we have had come through in the the years. Even with some quick repairs, we have not been able to keep the spout up during heavy rainstorms. We really have been very lax on that side of the house, because it is the least visible part of the we tend to neglect it more than the rest of the house. The damage is right at the joint of the downspout, where it angles out to the yard. That same section of joist is where our AC unit enters the house...the water pipe. We had to replace the entire unit this summer and we noticed that the water line was frozen and has been pretty leaky in the past. I think this all contributed to the borer beetles presence. We have a contract with Terminex and they are out every 3-6 months. We will be having them out again to take a look at the damage. The sill (the bottom board, that attaches to the foundation) is completely eaten/rotted away in about a 1 foot section, except for the inside 1/2" or so. That is only still there because while checking the wood, I didn't feel it prudent to remove that inside portion of the sill. There is litterally a 1-2" gap from the foundation to the rim joist, in about a 6-8" length. The rim joist is like butter in the same section. While it is a small section, the fact that it is on the corner is what worried me (actually the fact that it was part of the foundation of the house is what REALLY worried me!).

Thank you for answering, that is what I needed...a little confirmation one way or the other.

Answered 5 years ago by Guest_9276919


Since you describe that part of it as the consistency of butter, it is very likely the plywood subfloor below that (which the wall normally sits on top of) if you mean the bottom plate, or the rim joist above it if you truly mean a sill plate, is going to need some replacement too. If the rim joist is also rotten then the floor decking plywood may also need replacement - probably one joist spacing wide (18-24" typically) from the outside of the wall to the next joist or two over and maybe 3-5 feet long along one or both walls - so that will require putting in temporary supports for the wall(s) in that corner while the damaged sill piece (I suspect you are talking bottom wall plate) and plywood and rim joist sections are taken out and replaced. This also means you are most likely going to have that corner of your flooring taken up to replace the plywood if it rotted - hopefully carpet or snap-joint laminate that can be removed and replaced, not hardwood though it can be taken up too - just a bit more likely to be damaged here and there.

If the exterminator is coming to re-treat within a few weeks before the contractor doing the repair, I would suggest asking in advance (so he knows to bring it with him) if he can use a non-residual poison - let him know workmen will be removing that area soon, and he should be able to use an instant-kill poison that does not stay in the wood to be kicked into the air when the workers cut into it. And be SURE to tell the contractor up front that the area has been treated for bugs in the past, so they use correct eye goggles and dust masks/respirator to avoid exposure to the poisoned wood dust.


BTW - sorry I lost you in the terminology. Wall could be built several ways - simplest is that the wall sits with the bottom plate (the bottom horizontal 2x4) right on the foundation wall, bolted down and the floor joists tie into the bottom of the wall between studs - may or may not have a second treated wood 2x4 under it which would be called the sill or sill plate. If the wall bottom plate sits right on the concrete some people call that the sill. Looks like this -

Also called Balloon framing I guess - like in this article -

Second common construction method, more common these days, is Deck or Platform framing, where the floor joists sit on the concrete, with or without a treated sill plate under them (most code areas do require a treated sill plate). See Platform Framing images in above article and imagine the image shown as your corner. There is then a facing timber or plywood joist bolted or nailed across the ends of the floor joists that is called the rim joist, and the outmost floor joist that sits on the adjacent foundation wall would also commonly be called a rim joist even though it is really just one of the floor joists. That is commonly doubled up, especially under 2 or higher story houses, because it is carrying not only floor load but also the wall and some floor and roof loads from above. These joists may or may not sit on a sill plate of treated timber, usually a 2x6 or 2x8 - or sometimes have a "cripple wall - a short stub wall - under them to raise the floor level higher above the foundation without added concrete cost. Then these floor joists are covered with the flooring sheathing (plywood or (shiver down my spine) oriented strand board or particle board. Then the walls are built and tilted up on top of that and nailed into it, with the bottom plate of the wall sitting on the plywood.

On the gutters - closer interval downspout brackets (say 1 foot spacing) is something you can easily put in yourself and should solve your problem with it tearing off. Look like this - these are for plastic downspout, but look about the same -

If not available, put painted or treated wood spacer blocks between it and the wall so they fit tight like you would with the above bracket, then use plumbers tape (not actually tape - metal strapping with holes in it - looks like this -

and wrap that around it tight and screw to the blocking or wall on each side. Normally about 2-3 foot spacing, but in your case with evidently a high-wind corner, use about 1 foot spacing. If the downspout is angled out away from the wall near the top where it comes off the gutter, use sheet metal screws or pop rivets to hold the joints together.

Answered 5 years ago by LCD

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