Fixing exterior insulation

July 8, 2024 4:55 AM

I tore apart my front porch and found some previously loved insulation and what seems to be a skim coat of concrete. How should I approach fixing this before building the new porch?

Here's a photo of what it looks like now. Some people out there suggest that I can make sure the insulation is good and put some protection or flashing over it. Is that a good approach? Should I restore the concrete layer that was there? Should I dig down further to see if it needs fixing deeper? Thanks!

posted by transient to Home & Garden (10 answers total)

Should I dig down further to see if it needs fixing deeper?
depends how much energy/time you want to dedicate
posted by HearHere at 6:06 AM on July 8

Response by poster: Assume I’d like to do it as properly as possible given that I’m on my own. I don’t mind work.
posted by transient at 6:48 AM on July 8

I honestly can't tell what's going on there. The pink stuff at the bottom of the photo is foamboard insulation right? Do you have a basement? Normally, insulation outside on your foundation is pretty rare if you don't have a basement. It's a good idea, but it's rare. So if you don't have a basement and that's a cement slab foundation, then you should be able to put whatever you want in front of it. If it is foamboard insulation, it doesn't really require flashing, I mean you normally put something to keep it from moving around, but it can get wet and it's relatively bug resistant.

If you do have a basement, I don't have enough experience with those to comment.
posted by The_Vegetables at 7:12 AM on July 8

Best answer: Normally, insulation outside on your foundation is pretty rare if you don't have a basement.

In colder climates, the energy code may require insulation to go some distance below grade, and one method of doing so was to put it on the outside of the foundation wall with some kind of cover over it, basement or not. It's not uncommon at all, even going back decades.
posted by LionIndex at 7:16 AM on July 8

Response by poster: Yes, there’s a basement and it’s northern Vermont. Also, the drainage goes away from this side of the building (i.e. towards the camera in the shot).
posted by transient at 7:23 AM on July 8

Best answer: if it is foundation insulation, then it really just exists to create a barrier between the ground temperatures and the concrete temperature to make your home more comfortable. They might have got some concrete on it when doing some other job, depending on what was there before. The foam insulation sheet should go all the way to the bottom of your foundation, and then if you are lucky it's underneath as well. But honestly, if it's just a tiny piece missing, you can just cut a piece to fit over it and build your porch. Is the porch going to be attached to the home or not? Made of wood or a concrete slab?

Here's Canada's recommendation

If you can dig to the sides (or around some other side), you can see if it originally was flashed or not.
posted by The_Vegetables at 12:39 PM on July 8

Best answer: It looks like there's been some movement in that area, based on the horizontal cracking. Whether that's the case or not, my experience in renovating our home is that any job ends up easier and better if you remove anything that's not 100% back to the very basics and re-build rather than trying to deal with mess. Evey time I've tried to just do the minimum it's ended up more expensive, harder and not as good in the end.

I would remove the soil at either side and below, clearing back to where you can see material in good condition, remove whatever is sub-standard and replace what's needed. Then you can repair/rebuild what you need back to original and you have a sound base for whatever you add on.
posted by dg at 5:12 PM on July 8 [1 favorite]

Response by poster: I was thinking concrete steps attached to the house.
posted by transient at 6:45 PM on July 8

Best answer: I am a builder in Southern VT. This kind of insulation looks pretty normal to me. The skim coat of concrete is probably to protect the insulation from UV, pest, and impact damage. I would leave the insulation, assuming you have no reason to believe that it's improperly installed or your foundation has serious issues. I would re-skim with concrete as part of your future step rebuild project. You may be interested in resources on Frost Protected Shallow Foundations if you want to tie new concrete steps to your current entrance. It can help avoid the very deep digging necessary to avoid frost heave damaging the connection.
posted by Summers at 6:08 AM on July 13

Response by poster: Excellent info, thank you. Would it be better to have the steps separate from the building?
posted by transient at 9:10 AM on July 14