Hi,

We recently bought a 1940s house of questionable build quality and are in the process of fixing it up. We’ve lived in it for almost 2 years so I have a bit of a better idea of the issues I’ll need to address.

We are in climate zone 6 in Canada.

The house has a walkout block basement. I think they built it before string lines were invented, nothing is straight. I’ve built a 2×4 wall in the basement around the perimeter. I figured if I need to build straight walls in the basement I should build them load bearing so they are. The 2x4s range from nearly touching the block to about 4″ away from them. The basement leaks a lot during heavy rains.

The main floor is 2×4 construction. I built a 2×4 wall inside the existing wall after removing the drywall and wood chips so it’s now a double wall assembly. The interior wall is R12 fiberglass batts. I used 6mm poly as my vapour barrier. I then built a 1 1/2″ raceway for all my wires/boxes etc so there are almost no penetrations in the poly. It’s taped at the seams and accoustical sealant was used top and bottom as well. 

My current plan is to remove the original exterior 2×4 wall (studs and everything) and then build a 2×6 wall 24″ OC that is cantilevered 2″ over the floor diaphragm. I would first cover the exterior of my interior 2×4 wall with 1/4″ plywood (or maybe 3/8). This would be to keep the insulations separate and prevent my poly from blowing out since the drywall isn’t tight to it. On the exterior of the 2×6 wall I would sheath it with 1/2″ TG plywood. I would then blow the cavity full of cellulose. My plan is to leave access ports along the top plate so I can check for settling and top up the insulation for the first few years as needed. The plywood sheathing would be covered with Tyvek, then a 1/2″ air gap then probably vinyl siding.

The basement slab is uninsulated and also very uneven. I was going to lay down some 6mm poly, add 2″ of XPS, lay my PEX for in floor heat and then pour a 2″ thick slab on top of that.

The basement walls is where I am most undecided:

OPTION #1
With the 2″ overhang on the floor I was thinking of insulating the exterior of the block wall and rim joist with 2″ reclaimed XPS. This would be after excavating the perimeter and water proofing and adding weepers. I was planning on using a brush on sealant and then a dimple mat.

On the interior of the basement I was thinking of having it spray foamed and then topping up between the 2x4s with EPS then covering everything with 1/2″ drywall. I may hang plywood under the drywall to keep my kids from putting holes in the drywall. I would have the rim joist sprayfoamed as well.

OPTION #2
Essentially the same as option #1 but do all the wall insulation on the exterior. It would likely end up 4-6″ thick depending on what I can find for reclaimed XPS. I want to do 2 layers to stagger the joints. I would have to build some sort of cap for the insulation since it will now be proud of the wall above it.

I would leave the interior including the rim joist uninsulated to allow it to dry to the interior. I would only have 1/2 drywall on my stud wall, although again, maybe hang some plywood for the kids.

OPTION #3
Exact same as #1 except no insulation on the exterior. The rim joist would dry to the exterior.

QUESTIONS:
Which option looks best? My biggest concern is the sill plate since there is no gasket and I can’t add one.

Would having a Rockwool exterior insulation on the rim joist alleviate my drying concerns?

Does my double wall idea sound safe?