Our house is a bilevel, about 50 years old, wood frame, southern Canada. So winters here can get friggin’ cold.
The front entrance landing was constructed with a full-width 10-foot spruce 2x8 support beam right against the outside concrete foundation – and the idiots never installed any vapour barrier between the wood and the concrete. The height is just above grade.
They didn’t installed any insulation there or on the 40 square feet of bare concrete foundation in the crawl space below it, either. I’m fixing that with Styrofoam insulation on the concrete, but I can’t decide what I should do about that spruce beam.
If I were to insulate the beam, I’d normally expect to need vapour barrier between it and the concrete. But I’d have to completely rip out the landing to do that. I have to admit, there’s no sign of moisture issues on the wood right now. It looks like new. So that kind of project doesn’t seem to make sense to me.
If I put barrier and insulation on interior side of the beam, though, and add insulation there, I could wind up causing moisture buildup on the beam.
So I’m kind of thinking maybe I should just leave that wood bare. No insulation, no vapour barrier. Ain’t broke, don’t fix it.
Does that make sense?
I’m also only an amateur home renovator, but it seems to me your assessment is correct: if it ain’t broke…
Ripping out the beam and the landing to replace a beam that might rot and necessitate you ripping out the landing, doesn’t make sense, keep and eye on it and check a couple times year for signs of rot and replace as soon as it starts to fail. Rot is a fungus that will spread so it’s important to get it out at the first sign.
My first thought as you mentioned the interior insulation and VB was the same as your’s, you’d be trapping the moisture next to beam which would hasten the decay.
I would defer to an expert builder on this question but I’d agree, leave it as is.
There is another forum I use for renovating, home repair & woodworking advice you may want to check out: LumberJocks Woodworking Forum
If, after 50 years, there is no sign of wood deterioration, my guess is there may be a moisture barrier beneath the concrete foundation. It may seem unlikely but otherwise, the concrete would have wicked soil moisture up to the beams which should have cause some decay even if the beams had initially be treated against it.
Thanks all!
Good points made. I’m pretty positive there’s no VB between the wood and the concrete, but as it’s a foundation wall, a bit above grade, and this is a dry area, I don’t think any moisture is coming through anyway. I see zero sighs of that ever having occurred. I don’t know what the R value of 1.5" spruce is. Oh well.
Thanks for the feedback!
Accepted practice is for vapour barrier to be on the warm side of insulation. In new construction if wood is in contact with concrete, it should be treated. Sometimes a vapour barrier is placed between untreated wood and concrete but most people feel this is a bad idea. There is a foam gasket material that is sometimes used between foundation wall and main floor joists.
I see a lot of old basement walls with raw spruce plates directly on concrete. Sometimes they are rotten, often they are fine. I am not sure what exactly you are talking about - pretty sure it is not a beam. Houses of that age often had main floor joists and rim joists partially or completely embedded in foundation wall. The only time I see them rotted is when there is some other problem that has let water into the structure - ice dam, leaky pipe, roof or gutter leak, etc.
Insulating is rarely going to cause a problem, as long as what needs to stay warm is on the warm side of the insulation, and you do not allow water vapour to reach surfaces that will be cold due to the insulation.
Thanks!
I was all set to either ignore it or put a barrier on warm side of the wood (I think you’d call it a ledger board, it supports the front landing at the main entrance) when I found this:
“*Not to be confused with a vapor barrier—which is placed on the warm side of the wall just in front of the insulation and behind the drywall— a moisture barrier goes against the basement wall and behind the insulation and framing. *” here: https://www.popularmechanics.com/home/interior-projects/how-to/a20202/use-a-moisture-barrier-when-building-out-your-basement/
I dunno. I think I’m still going to ignore it. It’s bone dry and in perfect condition now, and I’m not in any hurry to rip apart that whole big main entrance landing area to fix something that ain’t broke. It’d be nice to insulate it a bit more, but I think I can live with R2 effective insulation along a 10 foot 2x8 in a crawl space under the front stairs.