SFGate

Brenda Fisher Is the moisture condensation or a leaky sill area? If leaking from outside the house fix that problem 1st. Insulating under joists
Requires a moisture barrier on the warm side. Then spray foam as it is your moisture barrier too. Foam panels are not recommended in this type of instillation as it would be difficult to seal all gaps to create that moisture barrier. 2 things to watch out for. 1: if your floor beams are imbedded in concrete walls do not spray foam them in at that location. Continue spray under floor boards the use bat insulation between joists, otherwise condensation at the imbedded joist ends will rot them. You will want to use a mould and mildew resistant batt. 2: spray foam off gases so you will need to close it in after especially if your return air for your furnace or air conditioner is located down there.

mommomjudy My basement is usually, dry except in heavy rain,the groundwater comes up from below floor and sump starts. Summer it is very damp because of high humidi
ity and condensation. This spring I plan on buying a de-humidifier for basement and draining it directly into sump. Thanks.

Cancork Floor Inc. I'm sorry to tell you this but your basement is not dry; it is very wet. You need to have your pad sealed. Without this, you will continue having all these problems. No matter what you do with the flooring insulation, you will continue to have mould and moisture problems. I've just had a client who did ALL the things you are THINKING of doing...and still she has mould/moisture issues!!! IF you don't get a concrete specialist in there to fix the original problem, you are bound to repeat this expensive cycle!

She even went so far as to have "infloor" radiant heat installed to "dry out" her slab. It then became DAMPER than before because she was evaporating MORE water off of her slab than before. Water moves down it's own concentration gradient (moves from "very wet" to "not so wet") because of capillary action. Be VERY CAREFUL what you do with a slab that is unsealed with a high water table and high summer humidity.

Your sump pump may not be enough. There are other things that can be done with that slab.

My suggestion: stop wasting money on the "interior" and start putting it towards fixing your wet basement slab. If you have not consulted a concrete specialist in your area, then you really should. This is not a "DIY" project.

mommomjudy It is not a slab it is a 100 year old stone walled original cellar,which we do not use. Everyone in our neighborhood experiences ground water coming in through the floor, everyone has 2 or 3 sumps for that resaon. We are in an area which hundreds of years ago was a creek bed(not in flood zone). Happens maybe 2 or 3 x a year when it rains over 3 inches.. We don't intend to do this insulation ourselves. We are hiring a pro . Have several cos. coming for estimates.