Which insulation should I use under my cottage?
my cottage is over a dirt floor, the foundation walls all in 2x6 and plywood, what type of insulation can i use on walls . and to point out the walls are sitting on contrete blocks no footing
my plan is to add a 6mil barrier to floor,
i eventually want to use in winter
thx denis
I’m going to read this back to you and please tell me if I’m reading you right – you have a continuous 2x6 and plywood foundation wall sitting on a continous block wall, I assume the 2x6 / plywood wall is all above grade?
Is the wall in good shape with no moisture or structural damage?
Are the blocks all above grade as well? I ask because the best way to do it will include some stuff on the outside and if its all exposed and not backfilled you are way ahead of the game.
How long has it been there and have the blocks heaved or cracked at all?
And what is your climate zone?
A good place to start reading is this page – How to insulate a crawlspace – walls and floors
We can help you formulate a plan to improve it, we just need to know the above questions first is all. The best move you could do though, is the 6-mil poly on the floor you mentioned. That will keep the moisture in the ground and help you avoid mold and be much more comfortable by keeping the humidity in a more reasonable range.
Where are you located Denis? What you are talking about doing here with an exterior waterproof membrane on the outside of the plywood is going to be a vapor barrier and prevent walls from drying to the outside. That's a bad thing to do in a cold climate, that's why your climate zone is important.
Blocks should not be on their side, that's not where their structural strength is, they should be upright with the holes at the top and bottom. I know this is a costly and labor intensive suggestion here, but ideally you would jack it up first and get the blocks on end the way they are supposed to be, that would also allow you to do a water proof membrane between the top of the blocks.
The blocks are really porous, so I just needed to throw that out there. If they are sitting in wet ground, or water as you mention, the blocks will stay wet and in turn wet the sill plate of your framed wall. So if there is any way you can get some poly between the block and the wood that's a really good thing, even if its just prying it up a half inch at at time to slip a waterproof membrane of some kind in there.