Am I going to create a moisture problem
So I am going to renovate the porch in my old house. Currently the walls are cheap wood paneling over broken plaster, and the flooring is very worn out carpet (not ideal for a porch really).
The plan is to gut the interior, fix anything that needs to be fixed, insulate/vapor barrier, and put down vinyl flooring.
However I am beginning to wonder about moisture from below. The porch sits on a separate foundation than the rest of the house (both cut sandstone foundation). Below the porch is inaccessible so I have no idea what is under there as far as space. I am assuming that any moisture below is currently moving up through the floor and is dissipating in the drafty porch.
By putting down vinyl flooring and vapor barrier am I just going to end up creating a moisture problem under the floor, or in the porch?
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Replies
Not if you put vapor barrier over the ground. Since you are tearing out the old floor covering I would suggest going one step further and remove some of the subfloor to create an access and put the barrier over the dirt and up the foundation.
I guess as long as there is room down there (l have no idea if there is a 12 inch or 6 foot hole under there) that would solve the problem.
I'll just have to poke my head down and see what surprises are hiding under there.
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You can also punch ventilation holes in the porch foundation.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
If the foundation under the porch is the same as under the rest of the house, then it is over 24" thick in most places. I think the vapour barrier would be easier than trying to poke a hole through the foundation.
Then again depending on the state of the mortar holding the stones together, I may be able to just pull a few out. I'll have to see when I get down there.
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Plastic over the dirt is probably needed, even if you ventilate the space. Be sure you seal the edges of the plastic to the foundation. You need a complete seal all the way around.
What is going to be the best option for sealing the plastic to the very rough surface of the foundation?
Run the barrier right up the foundation walls and fasten it to the sill plate. There in an article in Fine Hombuilding about making a moisture free crawlspace, go to the HOW-TO section and type in crawlspace and it will come up.
Edited 2/8/2008 10:39 am ET by Bridge_Dog
If you can't get to the sill plate, there are specialty adhesives. One is acoustic sealant, but I'm not sure if that is rated for outdoor temperatures and/or block. Assuming you have a block foundation.If you have a good waterproofing supply place nearby, go to them and tell them what materials you want to fasten. Otherwise, try searching out the major manufacturers web sites, like the PL people. Keep in mind what temperature extremes you have to deal with in your location.
angus....
if you have a stone foundation, very irregular..
we usually roll the poly up the wall about 6 " or so..
then pile sand on the edges to keep it in place
there will still be some migration of moisture right thru the stone itself.. so trying for a perfect seal is not time/cost effective
Mike Smith Rhode Island : Design / Build / Repair / Restore
So you're saying cover the dirt floor, and don't worry too much about the walls, right?
The foundation is stone but all square, cut sandstone, not fieldstone/rubble. They are variable in size (anywhere from 12 x 12 x 6 to 30 x 18 x 12), but they are all flush on the inside.
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walls will wick some amount of moisture.. but the fix is to put a membrane in at the grade level or below that isolates the wall section....
you can't do that after the fact...so don't worry about it or waste time trying to do anything about it
moisture levels are bad when they overwhelm the ability of the structure to cope with it
so wood can absorb a certain amount of moisture and not rot ( guess: 19 - 20 % )
keep the levels below that point and you won't have a problem
managing the moisture levels with a vopor barrier over the greatest area ( the dirt floor ) will probably solve your problemMike Smith Rhode Island : Design / Build / Repair / Restore
Thanks for the replies everyone. Gives me a couple of options.
I'll let you all know how it turns out in a few weeks.
Most of the family is curious to see what we'll find under the floor as no one has seen under the porch floor in living memory. Gramp lived in the house from '39 until I moved in in '04
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got up to PEI in 2001 after visiting Adrian for CaperFest
you have a beautiful island....
are the winters tempered at all by the sea ... or is it just plain cold ?
we live on an island in the middle of Narragansett Bay
it's always 10 deg cooler in summer and 10 deg warmer in winter than the mainlandMike Smith Rhode Island : Design / Build / Repair / Restore
Well I have to agree with you that it is pretty nice in the summer/fall.
Right now the Island weather leaves something to be desired. 12" snow last night and heavy snow for Wed.
Doesn't get too cold here in the winter. We'll see -20C (-10F I think) a few times, but mostly its around -5C (20F) to 0C (30).
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