Latest Discussions : Basement & Foundation


06:29AM | 07/07/04
Member Since: 07/06/04
5 lifetime posts
I am in the midst of finishing a portion of my basement. The previous owner had installed studded walls with no insulation on two of the four walls. The other two walls they used furring strips w/glue. I have since removed all of the old drywall and furring strips and installed new studded 2x4 walls. I also installed insulation, and read about a 6mil vapor barrier on the warm side of the wall, so I installed that over the insulation in part of the basement. I had only put up the vapor barrier in a small portion of the basement, and I have since put the project on hold for the last 4-5 months because of other projects. Last week I happened to notice major condensation between the plastic and the insulation. Now I am reading that I should not have a vapor barrier. I have since pulled down the vapor barrier and removed the insulation affected, and the wall behind shows no signs of water intrusion. The block walls were sanded and coated with multiple coats of Drylok before the studded walls were installed and the walls were bone dry to the touch, but warm.

I need to finish the project in the next couple of months, but am concerned about the condensation. It only happened in a 4x4 section, but I am wondering if I should put the vapor barrier up in the rest of the basement. If I keep up the vapor barrier and the condensation persists, will this cause future problems? Will it condensate on the new drywall without a vapor barrier? I don't know what to do!

There is not a huge problem with water in my basement, but I do run a dehumidifier.

Please help...I have a new delivery on the way in February and need to finish this project ASAP.

Thanks in advance to anyone that replies.

plumber Tom

03:48PM | 07/09/04
Member Since: 05/10/03
801 lifetime posts
You have made a huge mistake. The vapor barrier goes against the block wall or poured concrete wall. The insulation comes with a vapor barrier already on the outside (the paper side is the vapor barrier) You want that facing out. Rip it out do it right then you shall have some peace of mind that you know that the interior walls will not be prone to mold and mildew.


05:14PM | 07/09/04
Member Since: 07/06/04
5 lifetime posts
Tom...thanks for the info. However, I am getting conflicting thoughts on the subject of vapor barriers.

I read this on about 1000 different websites and books before starting this project, which is right? Against the brick or against the drywall:

"A vapor barrier in a basement should always be installed on the "warm side" of the wall. That means between the face of the studs and the drywall. Why? To avoid condensation on the vapor barrier itself, you want to avoid a large temperature differential from one side to the other. If you were to place the vapor barrier over the concrete wall, or on the outside of the studs (before the insulation), you would likely see condensation on the vapor barrier."

I have the paper side of the insulation facing the drywall. Is that enough for a vapor barrier, or do I need the plastic as well?


plumber Tom

08:28PM | 07/09/04
Member Since: 05/10/03
801 lifetime posts
I'll make it as plain and simple (laymans terms) as possible for you. 6 mil vapor barrier goes against the inside bare wall. It doesn't matter if your walls are stone, cinder block or concrete. Then the paper faced of the stud insulation faces the outside. good luck.


06:23AM | 07/11/04
Member Since: 11/06/02
1278 lifetime posts
Tom, You have unfortunately given the worst advice possible. There should never be two vapour barriers on opposite sides of the fibreglass, which is what would happen with the Kraft face out and the plastic in.

This is a link to the best and most informative site in the continent on this subject.

the fact that wayter condensed in the wall space under the pl;aastic is to me a suspicious sign that something is wrong in the whole scenario. That water got there somehow, either from leaking through the foundation wall, or from moisture migration allowed due to an insecurly sealed vapour barrier and then trapped there. IMO< If VB is not well done, it is better not done at all.

This basement might be better off with a foam panel baord that would tolerate moisture and would not support the groth of mold in a higher humidity environment.

Excellence is its own reward!


07:27AM | 07/12/04
Member Since: 07/06/04
5 lifetime posts

Thanks for your reply. You are right, the link was a very valuable source of information.

I'm not sure how to move forward. Should I remove the fiberglass insulation and replace with foam panel board? The studded walls are already in place and nailed down. Should I continue with the paper faced fiberglass insulation without a 6 mil VB? I was told that with the paper-faced fiberglass without a VB, any water vapors would disipate without causing fungal growth.

Again, I don't have a lot of moisture in the's about 65% right now, and the condensation only happened in a very small portion of the room.

Any thoughts would be helpful, I would rather not rip out the entire job.


03:45PM | 07/12/04
Member Since: 11/06/02
1278 lifetime posts
it's always hard to make specific recomendations for an area where I am not standing and looking because of so many times that I have been on a site and found specaial circumstances not otherwise described or apparant to the layperson, but based on the norm and my experience and general building conditiins on average, I would think you are as well off the leave the FG in place if it is not damp and milding, and then drywall over that. The greatest amt of moisture in your cellar will leave in an upward direction as you go through heating cycles, tho that is another variable.

Supposing that the ducting was originally designed for the upstairs only, then it might need modification to include circulating the cellar rooms air.

Excellence is its own reward!


03:40PM | 07/13/04
Member Since: 01/28/03
693 lifetime posts
If I am reading Plumber Tom's reply correctly he is right and Piffin is wrong.

The discrepancy comes in the terminologies and use of the words 'vapor barrier'.

The reality is that 6 mil plastic is indeed a 'vapor barrier' while kraft faced paper on insulation is a 'vapor retarder'

The two are not the same.

6 mil plastic NEVER belongs over the studs and under the drywall in a basement.

I believe that is what Tom the Plumber stated.

He said a 6 mil true vapor 'barrier' belongs against the block, masonry or wood foundation wall and that is correct.

The purpose of this barrier is to prevent moisture from entering the basement thru the block or masonery foundation from entering the living space.

However, a kraft faced paper is required on the warm side of the framed walls in front of the masonry walls so that during heating seasons the warm, moist air from the living quarters of the basement does not move OUT and into the colder masonry walls of the foundation and condense.

Unless I am misunderstanding both Piffin and Tom the Plumber, Tom the Plumber's answer is most proper and most correct.


04:30PM | 07/13/04
Member Since: 11/06/02
1278 lifetime posts
I don't know if you misunderstood either, but a plastic sheet against the inside of a concrete wall is the least correct way to keep moisture from leaking into a basement through a block or concrete wall. The purpose of a vapour barrier is to stop water vapours from entering the wall and condensing there. Warm air entering the basement will carry moisture in it. When warm aior hits cooler surfaces, it condenses.

Since the underground concrete is cool, moisture will condense on it. So, as demonstrated in Lsiturbrek's site, Building Science, the key is to always place the VB on the warm moist side of the wall, which in most cases as in this one, is the interior side of the studs. When faced with an ambivalent situation, where moisture can enter the wall cavity from either side, it must be allowed a way to escape again over time. In this case, if water is also leaking in through the wall, it must not be trapped in the wall cavity , but be allowed to osmose and evaporate. Plastic will prevent that.

Excellence is its own reward!


02:54PM | 07/31/04
Member Since: 07/30/04
2 lifetime posts
I agree a vapor barrier should not be used at all in a basement and concur that XPS is the best insulation material to use.

My question is a bit different - if I am going to put up a 2x4 studded wall with unfaced insullation batts against a concrete wall would there be a benefit to first gluing up some of the fan fold insullation that is only 1/4" thick against the wall and then mount the stud wall over it with the unfaced foam insullation between the studs.

The purpose would be to keep the insullation from touching the colder concrete to prevent condensation.

Second would there be any need to even glue the fan fold in place - couldn't I just support it in place with the 2x4 wall.


08:38PM | 08/06/04
Member Since: 01/28/03
693 lifetime posts
"I don't know if you misunderstood either, but a plastic sheet against the inside of a concrete wall is the least correct way to keep moisture from leaking into a basement through a block or concrete wall."

Again, based upon Piffin's reply he is worng and demonstrates he has little understanding of basement water/moisture problems and how to correct them no offense.

A plastic sheet on the inside of a basement masonry wall is one of the BEST ways to not only control liquid water fron entering a basement living space but also one of the best ways to channel water below the basement slab so long as the sheeting can be placed below the slab before pouring.

All due respect to Piffin but I see his basement vapor barrier information as "all wet" and he has yet to demonstrate anything differently or correctly.


07:27PM | 08/07/04
Member Since: 07/30/04
2 lifetime posts
Vapor barriers or vapor retarders are incapable of allowing foundation walls to dry to the interior. This is an issue. Simply leaving off interior vapor barriers and vapor retarders will not work due to the issues associated with interior vapor diffusion. Additionally, these two methods are incapable of being constructed in an airtight manner using typical production trades and materials and therefore are unable to address the air leakage wetting mechanism. The problems with these two common approaches to interior basement insulation manifest themselves in mold, decay and odors. Approaches to basement construction must not result in mold, decay and odors. The experience acquired by the Building Science Consortium has been reflected in changes that have been made to the Builder’s Guide Cold Climate (Lstiburek, 2001) as well as those for Builder’s Guide Hot-Dry & Mixed-Dry Climate (Lstiburek,2000) and Builder’s Guide Mixed-Humid Climate (Lstiburek,2001).

****** ALL ****** recommended basement interior insulation strategies involve placement of a layer of rigid foam insulation against the foundation wall.

The moisture sensitive interior wood framing and paper faced gypsum board are no longer in contact with the major moisture source – the concrete or masonry foundation wall such as can occur with water trapped behind POLYETHYLENE installed directly against foundation wall.

Moisture dynamics must be considered in detail before insulating a basement wall. Materials used to insulate a basement wall must be selected based on their ability to control the flow of moisture and air as well as heat. Selecting the wrong type of insulation or placing it in the wrong wall assembly often leads to moisture accumulation with subsequent material deterioration and growth of mold. A damp or wet basement that is improperly insulated will lead to deterioration of the building and promote conditions that worsen indoor air quality. A basement wall will remain dry only if it is built to handle all the different ways in which water can move into and through basement walls. Since walls will at times get wet in spite of good design and construction, BASEMENT WALLS MUST ALSO BE ABLE TO DRY. Drying typically means TOWARDS THE INTERIOR.

Basement walls can be wetted by liquid water (bulk flow and capillary suction) and water vapor. However, once materials become wet, they can typically dry only by the removal of water vapor either by evaporation or diffusion. Evaporation requires energy but insulation decreases the flow of energy. Insulated walls cannot dry as easily as uninsulated walls.

The rate at which water vapor moves through materials is “permeability”. Individual water molecules can move easily through permeable materials even if the materials do not permit air flow through them. Other materials are said to be semi-permeable to water vapor because they permit the passage of water molecules at a much slower rate. Materials that allow very little water vapor to pass through them are classified as impermeable. Air transport of water vapor requires an air pressure differenceas well as a pathway or opening between the areas of differing air pressure.

******A vapor barrier on the interior would prevent the walls from drying should they ever get wet.******

Insulating only on the interior side of basement walls presents problems because of ground water and the alternating direction of the vapor drive discussed above. The fact that ground temperature at various depths frequently is much colder than either exterior or interior air temperatures means that condensation can occur on the interior surface of the foundation wall. The interior basement insulation and the finished wall assembly are subjected to potentially significant moisture loads from vapor driven from both the exterior and the interior at different times of the year. While the building industry in the United States has become preoccupied in the past decade with vapor diffusion and vapor barriers in building assemblies, the problem of air-transported water vapor is often ignored. This is unfortunate because air-transported moisture is generally much more of a problem than is the diffusion of water vapor. Air transported moisture can quickly lead to deterioration in moisture sensitive materials. The entire consideration of water vapor has been complicated and confused by the fact that some materials can block the flow of air (an air barrier) as well as the flow of vapor (a vapor barrier). Some research in basement insulation systems has attributed moisture accumulation to vapor diffusion when airflow was not controlled. An effective air barrier is required in basement walls.

However, vapor barriers are typically not needed – particularly on the interior of basement assemblies.

The almost indiscriminate use of vapor barriers (polyethylene or vinyl wall coverings) over the past decade has caused many building failures and facilitated the growth of mold in many buildings. The permeability of materials must be considered before placing them in a particular location within a wall assembly. Otherwise water vapor may become trapped within a wall assembly where it can condense when the temperature is low enough. Any interior basement insulation strategy must successfully handle both the internal and external moisture loads. One proposed solution to this dilemma is to install a vapor barrier on both sides of the interior insulation system. The barrier against the foundation wall is often called a moisture barrier. The main problem with a double vapor barrier wall is that it cannot dry to either the inside or the outside should it ever get wet. In addition, it requires a perfect air barrier on the interior to prevent warm interior air from contacting and condensing on the cold foundation wall where it may be trapped. This type of construction should be avoided.

****** The major change in the past 20 years is the realization that a vapor barrier (usually polyethylene) on the interior side of the basement wall assembly inhibits drying of the wall more than it prevents wetting of the wall. *******

In testing walls that dried the fastest were the ones that did not have a moisture barrier against the foundation wall allowing the wall to dry to the exterior. Unfortunately this design would also allow the wall to become wet from the exterior likely causing condensation on the interior vapor barrier.

Many superficially dry walls will not remain dry when they are insulated. Many walls are dry because of “their ability to continuously evaporate soil-sourced liquid water to the inside.”

Basement wall assemblies with an interior vapor barrier can never dry if they become wet.

The widespread use of a double vapor barrier basement wall has resulted in many failures in some cases within one year of construction (Ellringer, 2002). Extruded polystyrene and cavity batt insulation, with and without a vapor barrier, covered by gypsum board were compared with walls having only a thicker layer of extruded polystyrene and an empty frame wall covered with gypsum board. The walls with an interior vapor barrier did not get wet from the interior during the winter but they did trap moisture during the summer when moisture is moving inward.

Without the vapor barrier, the fiberglass batts would remain dry if interior humidity is not excessive during the summer. Such low interior levels of relative humidity during summer conditions typically can only be achieved with active dehumidification provided by air conditioning or a dehumidifier. Walls with 3.5 inches of extruded polystyrene (XPS) and no vapor barrier performed the best. However,walls with 0.75 inches of extruded polystyrene and 3.5 inches offiberglass batt insulation in the cavity would perform well as long as interior humidity was controlled below 50 percent during the summer. Increasing the extruded polystyrene to 1.0 or 1.5 inches would improve performance even with higher interior relative humidity during the summer months. This part of the analysis assumed that the concrete wall had arelative humidity of 100 percent at the exterior temperature.

Any interior basement insulating wall system must have the following properties: It must be able to dry to the interior should it become wet since the below grade portion of the wall will not be able to dry to the exterior during any time of the year. This precludes an interior polyethylene vapor barrier or any impermeable interior wall finishes such as vinyl wall coverings or oil/alkyd/epoxy paint systems. The wall assembly must prevent any significant volume of interior air from reaching the cool foundation wall. Thus it must have an effective interior air barrier or a method of elevating the temperature of potential condensing surfaces(such as rigid insulation installed directly on the interior of concrete or masonry surfaces).Materials in contact with the foundation wall and the concrete slab must be moisture tolerant; that is the materials should not support mold growth or deteriorate if they become wet - some materials may tolerate being wet without blocking the passage of liquid water through the materials. A capillary break must be placed between these materials and moisture sensitive materials.

If a frame wall is placed interior to the rigid insulation, cavity insulation without a vapor barrier or retarder can be installed between the studs.

Wall Insulation with Foam Sheathing Covered with Gypsum Board either expanded or extruded polystyrene insulating sheathing can be attached directly to the foundation wall. Since extruded polystyrene is more moisture tolerant it should be used if there is any question about the effectiveness of the external drainage system. If additional insulation is desired, cavity insulation can be installed in a frame wall built interior to the foam insulationand covered with 0.5 inch gypsum board or other thermal barrier.


05:13PM | 08/08/04
Member Since: 11/06/02
1278 lifetime posts
Maybe I can be wrong sometimes, but as the above quotes from Joe's website demonstrate, if I am wrong on this one, the most respected and studied man in this country on this subject is also wrong.

That's life. I can live with it.

Excellence is its own reward!


07:06PM | 08/08/04
We all make mistakes (including me) but I would hardly characterize Lsiturbrek as 'the most respected and studied man in the country' in this matter since his advice conflicts with most all building codes for vapor barriers and proper basement contruction across the US. (maybe Piffin is in Canada?)

But after Domino's great handling of the vapor issues in a basement (with some disagreement) I thought I'd give my 2 cents toward his last response yet again:

First, vapor flow into a basement is from 2 sources:

One is from the wet ground into the basement thru the foundation...

The other is from the living space thru the framed wall toward the foundation.

Without addressing BOTH these directions of vapor flow we are all talking passed one another.



Vapor flow in from the soil, thru the foundation, occurs despite any temperature differentials, because the the soil outside the foundation is always generally "wetter" with more water vapor than the interior of the basement under most all conditions even when the soil vapor temperature is colder.

This means that even despite 'damproofing' of the foundation and basement temperatures being warmer, water vapor migration will be from areas of great concentration to areas of lesser concentration.

So the first major point of vapor transmission worry is at the foundation itself.

Without saying, the very best method(s) to prevent liquid and gaseous water transmission into a basement are from the outside.

Given that in most cases this cannot be done, the next best method is to deal with vapor and liquid water immediately at the foundation wall as soon as it enters the basement.

One acceptable method is to allow the water vapor to enter the foundation unabated and then deal with it from there.

This can be accomplished by the wholly acceptable technique of applying a 6mil polyethylene sheet over the foundation walls SO LONG AS this polyethylene sheet continues below the slab and footer or into a peripheral drain system so that any condensed water will not collect or pool in the basement.

Terminating the poly sheet above the slab does no good, since any vapor from without will only condense on the poly sheet and trickle down in pools on top of the slab.

This is also the drawback of using rigid foam panels directly over the foundation.

While rigid foam panels can decrease the potential for interior warm, moist air migrating outward from reaching colder masonry surfaces and then condensing (and let us not forget that the major proponents of these products are the rigid foam manufacturers themselves)...the use of rigid foam masonry panels alone does not prohibit gaseous water from without migrating inward and does not prevent this vapor from condensing between the foundation on the rigid foam and thus also trickling downward and pooling.


Rigid foam cannot accomplish this, but water and vapor proofing coatings on the inside of the foundation can.

By coating the inside surface of the foundation with a vapor and waterproofing paint, you achieve the very BEST of all possible foundation condensation preventions by never allowing outside vapor from collecting in the basement in the first place. A MUCH BETTER SOLUTION THAN USING FOAM PANELS.

You can STILL use foam panels in conjunction with a vapor proof coating, but foam panels should not be used alone.



Domino gave a very good explanation of how warmer (usually) moisture interior air from the living space will want to migrate out thru any framed walls and why a plastic sheet should NEVER be hung in a framed wall in a basement to prevent this migration.

The fact is, that warm interior air will want to migrate out toward the foundation walls in some situations and yet in other wish to migrate in from the outside in others.

Placing a plastic sheet in a framed wall never makes sense in a basement precisely for those reasons.

And while placement of rigid foam panels directly over the foundation walls will prevent condensation of water flowing outward by 'warming' the foundation surface, using foam panels without also vapor proofing the surface beneath only meets half the problem.

I have no idea where Lstirbrek gets his ideas since they violate all know acceptable building practice and code requirement for basements.

Unless his research affects certain locations it makes no sense for most of the US.

(And I will gladly be proven wrong)

But getting back to and addressing Domino's original question about placing 'fanfold' on the foundation then framing to it....

Unless you also water and vapor proof the foundation beneath the rigid foam beforehand....

AND unless you also install a kraft paper facing in the basement wall studs in front of the foundtaion walls...

AND unless you keep the framing at least an inch or two away from the foundation wall including the rigid foam...

It should not be done and may violate your State's building code.


As for Piffin, if you think I have handled you or your argument cheaply or worngly and did not offer you a fair shake...I will apologize in advance and still request further correction.

I do not consider this forum an arena by which any of us should disembowel the other for the public's pleasure.

I participate to be educated in as much as I strive to educate and if we all draw blood along the way, so be it.

Please, however, do not take my own personality quirks or disagreements as anything personal.

I'm an emotional, zealous type of guy and not fond of being proven wrong...but equally zealous and emotional for the truth when I am...

Respectfully submitted to Piffin, Domino and anyone else who wanders in...

And if you can enlighten me on Lsturbrek, I'll be glad.


06:25AM | 08/20/04
I'm starting to finish my basement this month and I want to be careful how I proceed. I've been reading through the various arguments posted here relating to vapor control and I've been visiting's website for about 6 years now and their vapor control advice makes sense. I certainly does not make sense to place a vapor barrier on the warm, moist interior side of a basement wall and trap moisture inside the wall assembly which can enter through the concrete. That much is clear. Anyone thinks this is ok only needs to read the first posting in this thread to see what can happen.

However, it also seems to make sense that I could avoid the process of gluing foam board insulation to my concrete wall (approx 35, 4x8 sheets in my case), by applying 6ml plastic vapor barrier directly to the concrete wall (a fraction of the time and cost), and build the wall assembly to the inside of the plastic with low-cost batt insulation. Further, since my region is considered "cold climate", I am considering building a 2x4 studed wall with 16" centers about 3 inches away from the concrete wall. I could then install 20" R11 batt insulation behind every second wall cavity, overlapping behind each stud. I would then place another 15", batt between the studs, alternating R11 & R20. This would have a similar effect to gluing the foam board behind the wall assembly, but would take far less time & cost to install.

Does this make sense to anyone? Has anyone ever tried this approach? I'm a "layman" when it comes to construction but if you agree with the principles as set out in, you would also agree that this approach might also work as well.



01:04PM | 09/05/13
I have stud walls installed in my basement about 3 inches from the concrete block exterior walls. I have limited money that I can spend fixing up my basement. What I want to know is can I install drywall over the stud walls without insulating inside the studs? I do know that I probably should put a 6 mil vapor barrier on the stud wall facing the room before I install the drywall is this correct?...thanking you in advance for an answer.....Brad


01:07PM | 09/05/13
I have stud walls installed in my basement about 3 inches from the concrete block exterior walls. I have limited money that I can spend fixing up my basement. What I want to know is can I install drywall over the stud walls without insulating inside the studs? I do know that I probably should put a 6 mil vapor barrier on the stud wall facing the room before I install the drywall is this correct?...thanking you in advance for an answer.


08:40PM | 12/21/13
Recently purchased house with one wall partially below ground. Wall is concrete and over time enough moisture has found its way through the wall to cause moisture resistant paint to flake off on inside of wall. Should I dig earth from around outside of wall and install some type of moisture shield between concrete wall and dirt?


09:45AM | 01/23/14
How do I get the 6 mil plastic to stay up against wall I stapled at top and put liquid nails but when glue dried it released from wall???


11:58AM | 05/06/14
I'm currently in the midst of refinishing a water-damaged basement in my home and here's my process thus far:

1. Exterior regrading of land and correcting drainage to eliminate standing water around the foundation.

2. We installed an interior drain tile system that connects to two sump pumps.

3. 6mil vapor barrier hung over, NOT adhered to block wall and then draping .5" into drain tile system to allow for air flow between block and VB.

3. 3.5" unfaced batting (R-13) in stud cavity. FYI, studs are approximately 6" from block wall.

4. .5" aluminum-faced foam insulation board (R-3.2) over studs and unfaced batting.

5. Drywall and then paint.


06:27PM | 08/29/14
i have a 4 foot wall.floor up.than studs another 4 feet i put strippeing wood. put strifoom in between wood and put a vaper bareer on and sheet rock over. now blocks are wet vaper bareer is dripping. what did i do wrong?


01:23AM | 11/10/14
What about the summer time when the warm side of the wall is outside?


10:10AM | 11/23/14
there is a duct wrap product that is 5/16" thick . double bubble wrap R-value of 4.2 and its plastic. why not use this as a vapor barrier against the block wall ?

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