rigid foam insulation

[EricU]

if they excavated anyway, it's a no-brainer, even though it has nothing to do with the water intrusion. The insulation on the outside will help the overall r value of your wall, and the energy savings can be significant.  I'm pretty sure a low-energy home with a basement would have it there, as well as under the slab.  The under-slab insulation is really common nowadays, and foam outside the walls is getting pretty common too.  My basement floor is quite cold in the winter, that's costing money in heating bills.  I wouldn't mind insulation under our siding, but the overhangs are so small on this house it would be a problem, particularly on the gable ends.

As far as water intrusion, i think I would go for belt and suspenders and belt approach. Try to keep the water away from the wall, have a french drain, and have a good drainage system at the slab. Having a drainage path to the slab seems like a good idea, because the water will make one if you don't. Had that problem with a previous house, what a nightmare. Didn't start leaking until after we moved away, so I had to get it fixed long-distance.

[brianwelch]

My basement used to leak because of the layers of clay in the area.  The water would run down hill along the layer of clay about 2 feet below the surface.  

I had three types of quotes for this job.  One type wanted to cut a moat around the perimeter of the basement floor and add a sump pump.  I was not happy with that type of work.

Another contractor wanted to dig a French drain which would interrupt the flow of water along the clay line.

The final contractor would dig up along the leaking wall, clean the wall and cover it with roofing tar. He also put up 2" foam panels outside the wall.  I'm not sure what that was supposed to do. 

I have since learned that there is a panel that resembles a 2" thick piece of scotchbright scouring pads with a permeable membrane on both sides.  This is supposed to allow water to drain even better than drainage sand.  

In any case it has not leaked in 20 years.  I don't know what the insulation panels outside the wall are accomplishing though.

In my limited experience, the purpose of the foam could be two-fold...one, the obvious, for insulation, and two, to protect the newly applied waterproofing membrane (roof tar) from being compromised/damaged during the backfill operation (stones, scrapes, etc)

[Cooler]

In my limited experience, the purpose of the foam could be two-fold...one, the obvious, for insulation, and two, to protect the newly applied waterproofing membrane (roof tar) from being compromised/damaged during the backfill operation (stones, scrapes, etc)

It is baby blue in color.  I trimmed it a few years back to the soil line because the color offended me.  


My neighbor had her house waterproofed at about the same time.  They didn't use drainage sand, and no blue foam.  It started leaking again about 10 years back.

[Anak]

In my limited experience, the purpose of the foam could be two-fold...one, the obvious, for insulation, and two, to protect the newly applied waterproofing membrane (roof tar) from being compromised/damaged during the backfill operation (stones, scrapes, etc)

 

The backfill protection is critical.  Otherwise that new waterproof membrane (roofing tar in this case) gets turned into a sieve.

[Cooler]

Thanks for all the replies.

Cooler

[brianwelch]

Thanks for all the replies.

Cooler

If you should go the rigid insulation route, please stay away from white "beadboard" foam (even tho much less expensive) and stay with blue or pink (extruded).

[Phil S.]

The 2" thick Foamair panels have an R-10 rating.  If I double up on this will it be equal to an R-20?

Also, this is scored to 12" widths.  If my studs are 14" on center then the space between studs is 12½".  Should I use a foam spray to fill in the gaps?

I'm doing the same thing.  Critters moved into the unprotected insulation and made a real mess of it, squirrels, wrens, wasps.  The floor was insulated with foil faced fiberglass stapled to the joists foil side out, lots of air exchange with the vapor barrier, such as it was, on the wrong side.  I found an article (In Fine Home Building I think, but now I can't find it) and more or less followed their recommendations.  I'm using 1-1/2" pink foam panels, mainly for a vapor barrier and air seal.  Cut them on a table saw for a 3/8" gap all around.  Glued them up with Loctite PL300 adhesive and used cap nails to hold the panels in place until the glue set.  Foamed around them with Great Stuff Gaps and Cracks sealant to create a vapor barrier and eliminate any air infiltration around the panels.  I hate using that stuff, especially overhead, but it got better after the first can when I moved quicker and didn't overfill the gaps.  Wear a hat and clothes you can throw away.  I roughly trimmed the foam after it hardened so any goobers hanging down wouldn't create air pockets.  Filled each joist bay with unfaced fiberglass batts and nailed 3/8" T-111 over that to keep the critters out and minimize air infiltration. 3/8" OSB or CDX would have been cheaper, but not look as nice. Used stainless nails to fasten it up (house is on a saltwater beach), 6" spacing on the edges and 12" in the field.  I just got it up so can't say how well that all worked, but it has got to be better than what was there.  The foam is rated at R-7.5 and the fiberglass at R-30.

Phil