Do I need a vapor barrier in my finished basement and if so how is it done?

Question

I live in upstate NY. I am finishing my basement. I have noticed in the summer months that it is extreamly damp in the basement. I am assuming I need a vapor barrier before I install insulation and finish the walls. Unfortunately the previous owners have already afixed 1x2's to the concreate walls so I cant paint on "dry lock" any ideas on how to go about this project. Any specific step by step instruction would be GREATLY appreciated.

Answer 1

To late. It should be dry before the stage you are at. are there are any  local authority in your area that is checking up on work like this. Do you have necessary permits etc. There seems to be  to be some thing wrong .Did you check whether all the work in your home is legal or what?  before you bought etc

Answer 2

There may be and should be waterproofing on the outside of the basement wall. Basements will be damp if they are not heated and cooled. If there is no HVAC you will need to ventilate it with windows or through doors. Run fans to circulate the air. Air conditioning draws the moisture out of the air and would help you on that.

Answer 3

If you have an "extremely damp" basement you have a water problem and shouldn't finish your basement until you address this issue.

I would not assume you need a "vapor barrier".

You don't  mention what kind of walls you have:brick, block, poured concrete, fieldstone, shale?  Brick, fieldstone, and shale foundations are older and were popular in times when foundations were not waterproofed on the outside.  The other two might have exterior waterproofing.

Think about how long you are going to have this house and this basement.  Think of how much money you are going to put into finishing it and then realize that you want to do the best job possible and protect your investment.  

If those 1/2 "furring strips" are problematic take them off.  Remember that any substance, drylock, thoroseal, even tar will last only 2 to 3 years if you have water coming through the walls.  It creates a pressure that eliminates adhesion and pushes the material off of the wall.  If you cover the walls up you will never notice that all the material has flaked off the walls.  

This kind of treatment is in any event only good for some kinds of water problems.  Here are  possible water problems and their solutions.

The first thing you need to check is drainage.  Make sure all your gutters are clean and functional, then that the downspouts are attached and working and last that something is taking the water away from the house and not letting it sit next to the foundation.  The ground around the house should be pitched away from the house and not toward it.  Some bad areas may need a concrete apron around the house (disguised as a sidewalk) to make sure the ground stays dry.  Those flower beds next to the houses that have loose Earth and are constantly watered are not particularly helpful for a dry basement.  Next make sure that there are no other leaking water sources around the house like a leaking hose tap.  All of these issues are best addressed on the outside of the foundation, but this is an expensive job to dig up the ground and install waterproofing on the outside.  And so people try to do it on the inside but it is not by itself as good.  

There are other systems commercially installed that pick up the water along the walls and guide it to a "french drain" that is along the inside of the walls.  This has the drawback of allowing water to do it's slow damage when it goes through the foundation but at least you don't have to suffer with it on the inside.  

But some houses are on slopes or for some other reason it is possible that the nature of the earth under the house is allowing once surface water to want to surface again under your house.  In this case the walls are not as damp as the floor itself.  In a retrofit (older home) situation your only choice is to install a drain.  Typically this takes the mechanical form with a pit and a sump pump.  There may also be french drains installed under the floor.  This has the effect of lowering the level of the water in the ground to below your basement floor level.

Finally, your last line of defense is a dehumidifier.  Set it up with a constant drain so you will not have to constainly drain it manually. It will raise the basement temp about 10 deg more than it would have been without it. (Or a ductless split air conditioner which is excellent at removing water.)

Extreme dampness without obvious water is usually eithor coming through the walls or the floor and it is the same as above and differs only by degree.  If you were to install a "vapor barrier" like (plastic sheeting) on new studs or the old furring strips and under any new sheetrock before you fix the water/dampness problem you will be setting up an ideal place for mold, rot, rust or decay to take place.  Bugs love this kind of environment too.  

Depending upon how deeply your basement is burried you may not want insulation, or at least not a full wall of it.  Basements tend to be naturally cool in the summer and warm in the winter.  This effect is from ground temp, the natural insulation of the ground, and part may be water evaporating.  Formerly I would insulate walls completely, but then found that I had modified the basements advantages.  Insulation is a buffer, it does not give heat it only slows it's eventual passage.  The basements were not quite so warm (in the winter) or quite so cool (in the summer) as they used to be.  Now I look to insulate only down to the frost line and pay special attention to the space between floor joist ends where they meet the exterior wall.  

Ventilation however is (like lighting) very important for a basement and for insulation. From the living space out you want to have 1. finished walls, vapor barrier (may be optional in a basement), insulation as needed, and a ventilation space.  Water vapor from the living space will go through the walls and insulation and you might be concerned if it condensed on cold exterior walls, but this is not a typical basement problem.  I am much more concerned about any water coming through the walls not being able to "dry out".  (And so my reasning behind no insulation or vap. barrier at least on the lower 1/2 of the walls in a typical basement.)

You have made many assumptions in your question.  I am glad you expressed yourself so fully.  Not everyone does and it is then harder to understand the situation.  I have tried to show why some of your assumptions don't match with my experience but in the final analysis you need to have someone give you advice after they take a look.  But you can look first though.  

I don't know what kind of walls you have, how old is the house, what are the grounds like, just how bad is the problem.  Seeing your situation I might taylor a specific solution that would be a combination of some of the above and other solutions.  Good luck with your project.  If I could not give a step by step at least perhaps you may understand the problem a little more.

Answer 4

The vapor barrier can be 4 mil poly, stapled to the strapping.  The other responder is correct about using A/C to dry out the air further.  You should be fine.  I live in MA, and this is commonly done.  Good luck.