I would like some advise on constructing a "mold proof" wall in my basement. Here's my situation, I live in western Washington and have fairly high humidity (compared to Arizona not Louisiana), my basement walls are poured concrete (about 2.5 yrs old) without cracks or other water problems. The space is about 3000 sq ft and I have a separate heat pump for the basement and run a dehumidifier.

I have been reading on this forum and other places for a long time and have heard contradicting ideas about what is the best way to construct a wall in front of concrete.

This is my idea so far:
Seal concrete
1" of spray foam-box style
1" air gap
Metal studs with styrofoam insulation
Drywall

In some of the cases I've read, it said that the vapor barrier caused the moisture to be trapped behind the walls and started growing mold, so I think I will go with white styrofoam and no vapor barrier to allow the wall to breathe.

The other idea I had was to eliminate the air gap and install a vapor barrier behind the sheetrock because the air will not have a place to condensate.

Don't bother asking what the local codes are, I will not be permitting this project. Maybe I'm a little testy about the government this week after writing a check out for over 6k in property taxes-and thats only 6 months worth- and don't even get me started about Federal Income taxes, sales tax, etc.

A little help here would be appreciated, especially if you did something similar, I just don't want to have a problem in a year or two and have to tear it all down.

Thanks for all the great inspiration. I thought I knew exactly what I wanted before, now I'm too afraid to drive the first nail for fear I'll change my mind half way through, and want to build something completely different.

[QUOTE=LJT]I would like some advise on constructing a "mold proof" wall in my basement. Here's my situation, I live in western Washington and have fairly high humidity (compared to Arizona not Louisiana), my basement walls are poured concrete (about 2.5 yrs old) without cracks or other water problems. The space is about 3000 sq ft and I have a separate heat pump for the basement and run a dehumidifier.

I have been reading on this forum and other places for a long time and have heard contradicting ideas about what is the best way to construct a wall in front of concrete.

This is my idea so far:
Seal concrete
1" of spray foam-box style
1" air gap
Metal studs with styrofoam insulation
Drywall

In some of the cases I've read, it said that the vapor barrier caused the moisture to be trapped behind the walls and started growing mold, so I think I will go with white styrofoam and no vapor barrier to allow the wall to breathe.

The other idea I had was to eliminate the air gap and install a vapor barrier behind the sheetrock because the air will not have a place to condensate.

my repsonse:
when you do double wall construction the outer wall gets colder than your inner double wall. aif the inner part of the outer wall gets below the condensation point of your rooms humidirty you get water condensing on the inner part of the outer wall. This happened to me, my solution was to use my prtable dehumdifier int he room every few weeks to dry out the walls and thus the whole rooms humdity stays above the condensation point.
does the above make sense? the inner part of the outer wall is the coldest place in the room and the humdity in the room will condense there. Only two solutions.
1. heat the room real hot (70 F) all the time. expensive and w aste if your not int he room
2. lwoer the humdity.

ttyl
rex

My idea was that by using spray foam on the cold concrete wall, the air would not condensate behind the sheetrock, but maybe that opens a whole other can of worms I'm not aware of.

LJT

I'm with you about the government, permits mean higher assessments. I don't really know what you can do to totally eliminate the possibility of mold but I know mold needs moisture, heat, and food(organic materials) to thrive. If you can eliminate one of these you will greatly reduce the risk of mold. Try to use as many inorganic materials during construction as possible.

There are also membranes available to waterproof your basement floor and walls.

I was afraid to drive the first nail as well because of all the great theatres and basements on this forum. I have gotten a lot of great ideas from here and actually feel confident that I have a good plan for my basement.

Have fun

Eric

http://www.buildingscience.com/documents/primers/plonearticlemultipage.2006-12-05.5229931729/section-2-recommendations

Do a search for basements on this site and you'll get a lot of information on moisture management. Basically you want to use extruded or expanded polystyrene insulation panels to cover all concrete surfaces and tape all the joints. (This will be DOW blue board or OC pink board, DO NOT USE WHITE STYRAFOAM). Then build your stud wall directly against the polystrene and insulate/drywall as normal.

Good question. I am in the middle of the same thing at my house. I installed a hydronic heating system in my concrete floor so my basement may be a little easier to manage. I put 1" John Mansville foam board along the walls. It has a vapor barrier on one side and an aluminum face on the other. I put the aluminum facing in for obvious reasons wanting to keep my heat in the room. I taped all the seams with Tyvek tape (Tuck tape or whatever other waterproof tape you want). I then put my studs (2x3's in this case....space is at a premium down there) with R8 insulation in the cavities. This is where I am not sure if I made the right move but I asked a couple of knowledgable people and followed there advice (although it may be overkill).... I put another vapor barrier on the studs over the insulation and then 5/8" sheetrock (I used cement board on one wall as it will be covered with stone). That is my solution. The only concern I have is potential humidity trapped within the walls as I put up the vapor barrier but I am probably overly paranoid. I just dont want to have a problem and dont want to cause any problems via overkill...

LJT

www.buildingscienceconsulting.com

Check out this site it has alot of useful info. Once you open the page click on "Homeowner Resources" then scroll down and click on "Foundation Insulation Systems."

Happy Reading,
Greg

http://www.buildingscience.com/documents/primers/plonearticlemultipage.2006-12-05.5229931729/section-2-recommendations

Do a search for basements on this site and you'll get a lot of information on moisture management. Basically you want to use extruded or expanded polystyrene insulation panels to cover all concrete surfaces and tape all the joints. (This will be DOW blue board or OC pink board, DO NOT USE WHITE STYRAFOAM). Then build your stud wall directly against the polystrene and insulate/drywall as normal.

What about a wall built 1'' away from the foundation, though, for sound isolation with double 5/8 and GG? Would you just use the insulation panels on the foundation and still come out 1'' before building the wall?

- J

The heated walls I think are a little overkill. I didn't go that far. My heated floor was strictly meant for comfort but as a secondary effect will help me manage my humidity as well. It's the double vaport barrier that worries me. Ultimately though, the walls aren't perfectly sealed. The only place I didn't tape on the 1st layer (the layer which rests against the foundation) is on the bottom. I taped neither the top nor the bottom on the layer residing just behind the drywall. I think if there is any humidity in between the walls it can escape out from under the wall or from the electrical boxes or somewhere there. I also have to opposing windows on opposite sides of this room so those can always be opened. One faces due north the other due south so there is always a breeze moving in one of those directions. It was mentioned during the winter about the top of the wall being colder than the bottom..... Before I put up the JM 1" stuff I had bigtime frost in at the top of the walls. I didnt have any heat nor insulation there and the cement was newly poured so it made sense. After I put up the 1st layer the frost seemed to all but disappear. With the air so dry in the winter time here in Quebec, I'm pretty confident that the foundation has a chance to dry out.

I decided on no vapor barrier to let the wall breath, a gap between the block wall and the stud wall, and lastly a dehumidifier in the basement that runs off of a humidity setpoint.

By the way, I also decided on no permits as my local county would not let a friend of mine who was a licenced master plumber in the state pull the plumbing permits solely because he was not insured with his own company. They wanted me to pay $7-8K for what I paid my friend $800 to do. They were much more concerned with being sued and collecting taxes than with any safety issues. I also found many code violations that the original builder was able to get away with, with the county inspection stickers right next to the violations!!! Some were safety issues as well, so their inspection means nothing, but who paid them the most money. I actually had 12/2 20A dedicated wiring (by code) for the upstairs kitchen, connected to the 14/2 downstairs lighting circuit. Not to mention they had broken the regulations around how many wires could be connected through one box. I found many, many other code violations that the original builder committed as the job progressed.

Either the insulation needs to go on the outside of the wall, or the room needs to be kept at the temperature of the soil. If one is attempting to address the problem solely through dehumidification, the humidity level must be kept extremely low (as close to zero as possible would be optimal, but less than 10% might be sufficient) at all times and air-circulation next to the wall must be abundant (fans should be kept continuously blowing on all parts of the wall and floor). Any type of insulation directly in front of the wall, especially if there is also a "vapor barrier" on the room side of the insulation, will automatically cause a mold problem (because it will inhibit air circulation).
http://www.monolithic.com/plan-design/belowgrade

While the added weight of an earth covering may not seriously challenge a buried structure, condensation will. South claims that when any underground house fails it's usually due to condensation on the inside, since such moisture becomes feed stock for mold and mildew. But what causes the condensation? South blames insufficient insulation.

He says, "Any home that's buried has to be super-well insulated. We have two reasons for insulating. Primarily, we want to contain heat by keeping it out or in. But, in an underground home, we also want to keep the surface temperature of interior walls and ceiling approximately equal to the temperature of the air inside the structure. That takes a lot of insulation, but not insulating properly will invite condensation."

I've been struggling with this dilemma as well as I'm getting started on my own basement. I'd be curious as to what others say about what I am thinking of doing as well.

I'm planning to put 1" of polystyrene foam board against my concrete block walls, then put up my 2x4 studded walls. Use a regular non-faced batted insulation between the studs, and then install sheetrock.

For where the walls connected to the ceiling I figure to cut out blocks of 2" polystyrene to fit and use spray foam and calk to seal.

Anyone have any comments on that setup? I'm located in Minnesota.

Two thoughts:

1)Asking about general building construction techniques in an audio/video forum would not be my first choice. There are lots of smart people here but very few of us are construction experts.

2)Local building codes are your friend. Even if for some inexplicable reason you want to do the job without permits, you can (and should) still follow the local codes to the letter. They may not be the absolute best way to do things but they are certainly going to be at least one way to do them pretty much correctly.

I'd be *extremely* surprised if Seattle didnt have different techniques for keeping things dry and mold free then dryer parts of the country.

Just off the top of my head there are a number of things you have mentioned that are incorrect:

1)Sealing the Concrete - wont help hardly at all, and may cause you to have effectively a 'double vapor barrier' leading to mold.

2)Metal studs - a no-no in the basement, IMO - especially in a high humidity climate.

3)white styrofoam, if you mean the beaded kind, is not the solution of choice for foam insulation IMO.

4)The idea is not to have no vapor barrier its to install the vapor barrier correctly.

Andy K.

Living in Canada, having a warm dry basement without moisture is a constant battle. I went through the same motions in finding out how to build such a basement. Suffice to say Canada's NRC (National Research Council) does provide info on how to frame and seal basements. Basically, how your foundation is built is key for moisture control. Here in Canada the accepted practice (by builders) is to pour foundation, weeping tiles around, tar seal outside, foundation membrane and chaulk membrane at grade. For inside (ie. DIY or builder), tar paper/builder wrap (this is a "moisture" barrier; not to be confused with a "vapour" barrier) starting *at grade* (important) going to the floor. The bare concrete above grade is for "vapour diffusion" which allows vapours in the stud wall to diffuse through the concrete to the outside (I know... hard to believe). Obviously, a 2x4 stud wall (I don't like metal) with gasket where ever wood touches concrete. This is then insulated with R13 fiberglass/mineral wool top to bottom *including* between the floor joists/headers. Next is a vapour barrier minimum 6 mil plastic starting from underneath the subfloor, taped/sealed around the joists to all the way to the bottom/slab sealed to the gasket under the stud wall sole plates.

Note all OPENINGS in the vapour barrier have to be sealed including around J-boxes/outlets. Such holes can allow almost a cup of water to pass into the cavity. Remember, you cannot perfectly seal a foundation (hey, concrete holds water :) and seals fail in time) you just need a way to allow the moisture/vapour that does exist (and it will always exist) to escape. In this case, its the vapour diffusion that does it. Also, note that the vapour barrier always go on the warm side, insulation and moisture barrier (which doesn't need to be sealed hence tar paper is good enough) is always on the cold side.

Of course, such techniques may work in one area (like Canada) but be inappropriate in other areas. Hope this helps...

Cheers,
Kaoru

LJT

www.buildingscienceconsulting.com

Check out this site it has alot of useful info. Once you open the page click on "Homeowner Resources" then scroll down and click on "Foundation Insulation Systems."

Happy Reading,
Greg

Thanks Greg,

Thanks for the link, I think I saw this link a while ago and this maybe where I got my ideas from. It appears the insulation in the wall must be semi permeable, not the pink or blue sheets. Did anyone use this method?

I thought this might be a good place to get feedback on basement construction because most guys are spending a lot of time and money and want to get it right the first time. I know a builder, and he told me they just buid basements like any other wall and plan on tearing it out when it gets mold on it! I guess this is because most people in this part of the country don't have basements, and don't know how to build in them.

I'll never understand guys that wont use galvanized steel studs, but are OK with wood that feeds mold, and wicks water if it ever gets wet. I guess everybody has thier own opinions.

Thanks for all the comments, and ideas.

Lance

I didn't use a gasket material underneath my wood studs with I placed on the floor. I didn't think about it at the time. Again, my floor will be heated so hopefully I will have less problems. I looked at the existing walls down there and there is no gasket material underneath them. I figure since they are not rotted and show no signs of mold or anything after 25 years then I should be okay. I would have to agree though that it is probably good practice to do so. I'm still going to lose sleep over my 'double' vapor barrier. Does fiberglass insulation absorb moisture the way concrete does? If so there wont be a way for it to breath if I have a vapor barrier on each side. Any moisture that would enter the walls would be primarily from inside the room since I have a vapor barrier directly against the concrete. I think I will just stop thinking about it and hope that I have done the best.

I'll never understand guys that wont use galvanized steel studs, but are OK with wood that feeds mold, and wicks water if it ever gets wet. I guess everybody has thier own opinions.

Thanks for all the comments, and ideas.

Lance

Given that wood is stronger, easier to work with, and is more forgiving if mistakes are made is why I use it. As for food for mold, that's nonsense... mold will grown anywhere including on metal, it just needs water (the dust in a cavity is more enough food!)... The whole premise for stopping mold, rot, water damage, etc. is to have cavities breathe some way to remove vapor while stopping moisture. This applies to roof, walls, any part of the home. A roof/attic has to breathe or it will rot/grow mold hence. In all cold/warm interfaces in a home has the same principle applied. The cold side always has a moisture barrier to stop liquid water, insulation to stop condensation (heat transfer doh!), venting to remove the water vapour that's always there, and a vapour barrier to stop water vapour build up.

Cheers,
Kaoru

I didn't read all of the replies so you may already have your answer but a great place to start for advice on how to go about a renovation is at http://www.mikeholmesfanforum.com/. Not sure if you've heard of Mike Holmes, but he usually does things the right way.


One of the reasons I've heard for not using Metal studs for the outer walls is that it more easily transfers heat/cold which can more easily result in the formation of condensation. That then leads to rusting/mold problems.

Thanks Greg,

Thanks for the link, I think I saw this link a while ago and this maybe where I got my ideas from. It appears the insulation in the wall must be semi permeable, not the pink or blue sheets. Did anyone use this method?

I'll never understand guys that wont use galvanized steel studs, but are OK with wood that feeds mold, and wicks water if it ever gets wet. I guess everybody has thier own opinions.

Lance

Pink or blue polystyrene is semi-permeable. I used it for my basement and wouldn't do it any other way. If you have a water problem where there is actually visible water in your basment you'll need to get a sump system with a channel all the way around the floor. It would definetely require a professional basement contractor. As for galvanized steel studs, they WILL rust and I've personally seen it. Plus, nothing like the smell of sawdust in the air. :)

A few rules for basments:

DO NOT SEAL THE CONCRETE, it needs to transfer moisture both ways
USE POLYSTYRENE ON COLD WALLS/FLOORS, it will create a thermal break which prevents/eliminates condensation forming and act as a vapour barrier. Ideally you would have it on the outside of the foundation.
DO NOT USE A VAPOUR BARRIER(other than polystyrene), it traps moisture which is bad.
USE TREATED LUMBER/GASKET(or both) FOR SILL PLATES

Localmotion: It sounds like your basement is very dry so you're lucky in that regard but I would be concerned about the double vapour barrier. I wish I could reassure you that it will be fine or that you hadn't drywalled yet. :( It may be okay though, just try to keep an eye on your moisture situation however you can; ie: pull out your vents or outlets occasionally and look for signs of moisture on the vapour barrier and insulation.

I do work in the construction industry. Don't use Vapor Barrier on your walls. Waste of time & money although it's not that much. To keep mold down, as has been said, keep the humidity low and you'll be fine.

just to add....a lot of people advised keeping room heated well....yes this will help prevent condensation, BUT your relative humidity can shoot through the roof.....hot air holds far more moisture than cold air.

i would avoid temperature as a solution and stick to a dehumidifier as a primary workhorse, use temperature to make the dehumidifiers life easier.


***edit, the actual amount of water in the air shoots up in a non-linear fashion as RH increases and temperature increases***

I struggled with a solution to this very problem for about five years.

Last spring we got water in the basement AGAIN! Only this time it was far worse than ever before: it was a backed up sewer problem. I would NEVER consider puting wood in a basement due to some unbelievable mold I seen in my days. So, I decided metal and drywall were the answer. After the sewage (never had that happen before). I decided that I needed to bite the bullet and work with a material that could be cleaned and sanitized (bleached) if need be.

So, last novemeber I started laying lightweight ( a relative term, believe me) cement blocks to finish our 2400ft. basement. I've got 2k worth of blocks laid and could not be happier. Was it a lot of work-um, yeah. Am I worried about mold or water damage, nope. Was it permitted? Ha. Those taxing devils take from those who work to distribute to those who don't or who scam the system out of MY fricking money! GRRR.

The interior walls will be stuccoed right on the concrete. The STC of 8" concrete blocks is around 30. No need for double walls and GG down here!

The exterior walls have 1" blue poly where it is earth sheltered and 2" polystyrene where the basement is exposed to outside elements. The inside polystyrene will be stuccoed just like the Dryvit system is and will match the interior walls. The stucco will help reduce the considerable fire (smoke actually) risk in an emergency of the polystrene which smokes something fierce. Since the majority of people die of smoke inhalation, not being burned, that was an important consideration for me.

So, no double walls and moisture vapor problems. Lots of easily cleaned concrete. If I start to get a mold problem somewhere I'll of course add a dehumidifier to the area and then bleach to my hearts content and clean the mold up.

I'm only 38 but having owned several rental properties and of course our own homes, I've seen a LOT of water lines break for lots of reasons, from freezing to rodents chewing!!!! I am absolutley amazed that putting wood against concrete is an accepted practice for basements. I've got a wood/drywall bathroom in a basement that I have to remove now because of extensive mold problems. Am I like the unluckyest guy on the forum? The only one with water damage in basements? My local insurance agent told me she pays 10 to 1 water to fire damage.....I always have 1k deductables and the next time the solenoid on the dishwasher decides to fall apart and flood my soon to be finished basement I'll just replace a few ceiling panels and sweep the water out the back door. $50.

Good luck!

joe

Below are various cites I collected that explain how vapor barriers cause mold problems in basements. you can get the two FHB magazine articles on their website online with a membership. (it's a very good magazine)

http://www.buildingscience.com/documents/primers/plonearticlemultipage.2006-12-05.5229931729/section-2-recommendations/ (very good!!)
http://www.buildingscience.com/documents/primers/plonearticlemultipage.2006-12-05.5229931729/section-2b-recommendations2014air ("One of the worst assemblies for basement walls from the perspective of mold and moisture problems is a foundation wall that is internally framed and insulated with fiberglass cavity insulation and covered with a plastic vapor barrier."
http://www.eere.energy.gov/buildings/building_america/pdfs/db/35398.pdf
http://www.eere.energy.gov/buildings/building_america/pdfs/db/35017.pdf
http://www.buildingscience.com/bsc/resources/foundations/Understanding_Foundations.pdf
http://www.buildingscience.com/bsc/resources/foundations/basement_insulation_systems.pdf
http://www.buildingfoundation.umn.edu/OCBasementSystem/ProjectReview.htm
http://ths.gardenweb.com/forums/load/basements/msg1013404110282.html?4
http://www.newsday.com/features/home/nyp-hsdr-082505,0,452831.column
http://www.housingzone.com/proremodeler/article/CA6358797.html
http://www.huduser.org/Publications/pdf/moisturehomes.pdf (p. 54, 84)
Fine Homebuilding No. 169 March 2005 p. 78
Fine Homebuilding No. 162, May 2004 p. 52
http://www.housingzone.com/topics/pr/build/pr04ca007.asp
http://www.housingzone.com/proremodeler/article/CA6404480.html
http://www.simplyinsulate.com/content/tips/ICCAVapor.html "it is recommended that a vapor retarder not be used in a wall that is partially or fully below grade."
http://www.buildingscienceseminars.com/2006/handouts/BSD-103_Understanding_Basements.pdf

That makes 3 out of 22 replies that have the buildingscience website linked. I think anyone with questions at this point isn't doing enough reading. ;)