Block foundation waterproof and insulate

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  #1  
Old 01-08-03, 09:41 PM
KSS
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Block foundation waterproof and insulate

Hi,

First post here but I love all the great posts I have read so far. I have gutted my basment to the foundation walls. They are conc. block and I noticed about 10 sq/ft of mold or mildew. I cleaned it with bleach and it looks to have been killed. My question,

I will be using 2x4 wood studs with roxul insulation what do I do to the walls before studding and insulating to keep out dampness and moisture. Any and all suggestions would be appreciated. I have read many posts here about this but none were for block walls with a parging material coating the inside walls.

Thanks

KSS
 
  #2  
Old 01-11-03, 04:03 AM
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Whether poured or block the method is the same for both. But before you do you want to make sure you have the cause of the mold taken care of. It would be a cheap exercise to first paint the walls with a concrete sealer. Then apply a poly "moisture barrier" against the wall from grade level to basement floor. Let about 6" of the poly lay on the floor. Fur the walls with the 2x4's with the bottom plate on the poly. Insulate leaving the batt insulation 4-6" off the bottom plate. This will keep the insulation dry if you have minor flooding and heat loss is minimal if this level is below frost. Now apply another sheet of poly (vapour barrier) over lapping and caulk the seams covering all batt insulation. Between joists at the rim joist you will get a better job if you use rigid polystyrene cut to size and caulk around the edges. There is no need to cover the rigid insulation with poly. If you are going to carpet the floor invest some money to vapour barrier,strap & sheath the concrete slab ( no insulation if below frost). This will greatly improve the comfort level of the room and keep mold out of the carpet.
 
  #3  
Old 01-11-03, 11:28 AM
KSS
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Thanks for the reply. I appreciate your help very much.

KSS
 
  #4  
Old 01-12-03, 08:45 AM
D Pell
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I used hydraulic water stop cement on my walls befor I did any frameing.I mixed it up soupy like and brushed it on using a 6 inch brush witch i got from Home Depot.This work out real well for me.And only cost me 50 Canadian dollars..
 
  #5  
Old 01-13-03, 02:39 PM
Brewbeer
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Building Science Corporation has done some excellent research on various basement insulation systems.

Basically, BSC strongly recommends AGAINST using poly vapor barriers in basement insulation systems that are installed on the interior side of concrete foundation walls, due to the problems associated with moisture movement through concrete and the potential for mold growth fed from moisture trapped inside the wall by the poly.

BSC recommends that concrete foundation walls be insulated on the outside. However, this is not always practicle. As an interior retrofit option, BSC recommends using extruded polystyrene between the concrete wall and the stud wall, and if desired, un-faced fiberglass between the studs.

Check out BSC's basement insulation study at this link:

http://www.buildingscience.com/resou...on_systems.pdf

Good luck.
 
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Old 01-15-03, 11:33 AM
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For Allan:

If I follow you correctly, you are saying to place poly on the foundation walls, put up the studs, install the batt insulation, and then apply another layer of poly over everything.

What I don't understand is where you wrote "caulk the seams covering all batt insulation."

How do you caulk a flimsy plastic material such as poly???
 
  #7  
Old 01-15-03, 07:40 PM
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KSS,

I guess I better say something, Brewbeer seems to have alot of things to say about BCC but fails to point out issues that are important to the average consumer. Most that post here are dealing with existing structures, most do not have insulation placed on exterior walls and most are dealing with older homes. The ones that "breath" compared to now. The rules that apply here are different and postings should address these differences. Allen seems to have a strange way of doing basement walls, leaving 4" to 6" of insulation off the bottom plate means that the "cold", which falls will flow at the level your children are playing at? Most importantly if there is no vapor barrier like poly or kraft faced insulation there, any moisture problems that exist will attack the wood and drywall backing where mold and mildew will spread like wildfire. Allen points out a good point, sealing your concrete walls - this is overlooked by many and when you start to insulate a lower level, you are creating a barrier between cold and hot. The difference in temp between the heated and block wall will create some condensation on it's own but this is minimal and does dry up. For this reason, taking the time to prevent or minimize moisture issues is essential. These issues if you have them should be addressed before you undertake major remodeling in a lower level. You should never use rigid insulation in the rim joists. One is they are extremely toxic and is required by code to be covered. When used within the interior of a basement, placed against the block walls, and protected with drywall and the ceiling is drywall, that may be ok but questionable. If it is a drop ceiling, then fireblocking must be used or other methods to seal the rigid if used on block/cement walls. It is highly advisable to use batt insulation, preferably kraft faced for these areas, most common is R-19 minimum rim joist insulation in most places.

There are many variables to consider in the applications of wall framing and insulation. I have never heard of caulking poly, the poly should be overlapped regardless, no need to caulk. Mold and mildew are formed because of continual presence of moisture and a great food source like wood, carpeting, drywall backing, paper products. Also for those that didn't know it, water resistant drywall (greenboard) has been noted as the best source for mold growth once becoming wet. This is why cement board was created and used now so widely. It can handle the high wet areas like showers and tubs with no worry. Lack of air movement to dry in these areas and no preventative measures to stop the moisture is a good way to see how fast this stuff spreads.

I have address the proper method for doing basements with alternative methods.

I guess this is the best and most economical way to construct walls that would be placed on the exterior. I prefer to see 2x4 but as mentioned by others they can get 2x3's. You still need that W/T plate. Doing the framing 16" O.C. provides a solid base for your 1/2" drywall. Walls are to be framed out from masonry/concrete walls at least 1" when not using rigid insulation.

The reason to keep the wood out from the walls is the moisture that could damage them. Using larger insulation like R-19 would touch the walls. I have stated before that if a homeowner did put thicker insulation in, and the wall was only 1" from the masonry surface, I recommended hanging a vapor barrier between the back of the wall and masonry surface. THIS DOESN'T ALLOW FOR INSULATION TO TOUCH THE WALL AND AIR MOVEMENT IS NOT RESTRICTED. THIS WON'T ALLOW YOUR INSULATION OR WOOD TO BE DAMAGED. If you do want to increase the R value, move the wall out further or use the R-13 and then apply a rigid insulation over the studs (warm side) then drywall (not paneling) *Code advises a 15 minute fire rated material over any rigid insulation - 1/2" Drywall* You can then put paneling over this if desired to met code.

Kraft faced insulation is fine to use in the above scenario. If you do, you do not need to apply poly to the warm side. You may find this easier and I would do this versus unfaced and vapor barrier because I don't like to play with it any more than I have to.

Let me add one other thing, rigid insulation used on a concrete/masonry surface is fine. Considerations to make in using this is;

1. If you are just using 1 1/2" rigid and furring strips - A. You need W/T strips to protect the wood. B. The strips can be adhesively applied but they must be solid - mechanical anchors may have to be used to insure that if shelving is installed it will hold. C. Any electrical boxes will have to be shallow - sometimes makes it hard to wire. D. You must use a fire retardant material over this as per Code.

(Most books, articles about rigid and furring strips fail to say anything about the use of W/T and this will get destroyed and be a good source for mold/mildew with the slightest hint of moisture)

2. Alternative which does add cost is to apply full rigid sheets to the concrete/masonry walls, adhesively applied, then place frame wall against the rigid, then insulate between studs and cover with drywall. The rigid does then act as a vapor barrier and rigid insulation does breath. Do not tape/seal the seams. This allows it to breath and dry up any condensation that may form.

Hope this all helps!
 
  #8  
Old 01-15-03, 10:12 PM
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Mr. Aleshire, I don't know where you get the time or energy to write so many lengthy contributions, but I enjoy reading your imput.

Anyway, quick question (but a lot of background). I recently did my basement up here in the Boston area. The house was built in 1987 with the full basement untouched other than that the foundation walls being painted a bright white (I think it was normal latex paint cause I found the almost empty paint can stored on a shelf).

In the 3 years I've lived here, there has been no evidence of water seeping either through the walls or up from the floor.

Anyway, this is what I did, and I was wondering if you could comment on whether you think I should be ok or not:

I left the walls painted as they were. I used metal/aluminum 2x3 studs all around the perimeter and for the bottom track (spaced about an inch away from the wall). I then placed R-13 kraft-faced fiberglas insulation between the studs and then put up drywall and then plastered (the kraft side of the insulation facing the drywall). To be honest, the insulation may be pressed up against the concrete walls; I just pushed the batts between the studs and they held themselves up until I put the drywall over everything.

Three of the four corners of the basement are not insulated. That is, I put a 1'x2' closet with a narrow door in these three corners (one houses the electrical panel, one the water meter, and the other the clean-out pipe). I figured I'd mention this cause in a sense I guess this allows some breathing room (maybe true, maybe not).

Finally, I installed a de-humidifier and during the summer and early fall it ran quite a bit as, I'm sure you can imagine, there is a lot of moisture in the air. Since mid December it hasn't run at all.

So, can I sleep at night knowing I didn't make a major no-no? Thanks.
 
  #9  
Old 01-15-03, 10:36 PM
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azzurri,

First off, "Mr. Aleshire" makes feel old! It's Doug!!

Second, Thanks for the compliment, I think. Others may not always like it but if you don't say it like it really is, don't say nothing at all! I hope what I posted was explicit so all understand how things work. Because I do alot of design and drafting, I am usually here and I need breaks too. This has been good for me as well. I learn from others and others learn from me, it's a good deal all the way around. Between my web site and this and my business, I am usually pretty busy!

Third and finally, you can sleep good at night, I would have to agree with you that what you did sounds fine. The issue of using the dehumidifier during the summer is a great idea because when winter comes you want some humidity or your nose and lips will dry up and whatever else in the house might be effected, like hardwood floors.

So sleep well and enjoy your lower level! Thanks again.
 
  #10  
Old 01-16-03, 08:51 AM
KLE
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Doug,

I also enjoy reading your responses, and appreciate your time and educational imput.

Three questions,
1. If ridgid insulation is attached to the foundation with furring strips and then covered with drywall should a poly barrier be placed over the rigid before hanging drywall, if this was done is their a problem with it ?

2. Is a .25-.50 space between foundation and back of insulation enough space for it to breath? The basement is always dry.

3. If I follow your alternative method #2 and hang rigid then stud then add insulation between studs should the insulation be Kraft faced?

Thanks for your help!
 
  #11  
Old 01-16-03, 09:19 AM
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KLE,

Thank you for the confidence! I'll answer these as you listed them;

If rigid insulation is used, it is suggested by manufacturer that no vapor barrier be used - these products do breath and thus no worry about condensation reaching other materials.

As I mentioned before, a space of 1" is recommended when using batt insulation/wood framing. This was for protection of wood and insulation from touching the block walls. I only recommend hanging poly over block walls should someone install thicker insulation than the depth of a 2x4's and has a minor damp walls. I still recommend waterproofing the walls with Drylok or other products before doing any finishing work.

No use of vapor barrier is required when using rigid, so the insulation that you use between studs should be unfaced.

Hope this helps!
 
  #12  
Old 01-16-03, 02:34 PM
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Hi Doug, thank you for all your efforts as a moderator on this board. Your information and assistence is very helpful to me and to countless others as we all wade our ways through the various homes projects that we are undertaking.

I'm not in any way affiliated with Building Science Corp., and just happened onto their study when I was doing a search on basement insulation systems.

These folks recommend that for new construction, foundation walls be insulated on the outside, as the best solution to prevent the growth of mold on basement finishing systems. This situation doesn't really apply to most of the folks posting here.

Although much of the BSC study that I suggested (as research material for folks finishing a basement) is geared toward new construction, there is a portion of the study that addresses retrofits of existing buildings. Moreover, the science and physics of water movement through concrete foundation walls are the same for exisiting buildings and for buildings under construction. Understanding the science and physics of this water movement is a good idea when determining what materials an average homeowner should use in their basement re-finishing project.

I would think that the biggest issue that the average consumer would care the most about, would be constructing a basement insulation and finishing system that prevents the formation of molds that can cause health problems to themselves and their families. This is my biggest concern.

For retrofit of existing buildings, they recommend an insulation system that does not contain impermeable barriers, becuase concrete is essentially a "sponge" and needs to "breathe". Their science/logic is that if you prevent the concrete wall from breathing, moisture that normally flows through concrete (whether you want it following through there or not, it does) and evaporates, can't, and thus condenses on the poly surfaces, which cause the wetting of building materials, and the subsequent growth of mold.

One important thing to point out here is that the BSC folks STRONGLY state that when basement insulations systems are installed on the inside, a dehumidifier (or AC) is pretty much required (in the summer in my area, or when ever the air is humid) to keep humidity levels low enough to prevent condensation and the subsequent growth of mold.

I had to read this study several times before I fully understood what it was saying. All I am trying to do is help folks make their own, informed decisions, by pointing out the experiences of other who have studied the problem of mold growth in basement finishing materials.

As Do It Yourselfers, we are all ultimately responsible to make our own educated decisions about what is best for us in our projects.

The BSC study has been a real eye opener for me, and once I understood the physics of the movement of water into and out of concrete walls in basements, there is no way that I would ever use a full poly barrier in a basement finishing system.

Thankx for your help Doug, and best of luck to all the DIY'ers out their with their projects !!
 
  #13  
Old 01-16-03, 07:05 PM
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Azzurri
The caulking is done at the nearest stud giving you a solid backing. Even though the drywall will be pressed against the poly there is still space for vapour to migrate into the insulation at the overlapping poly. Caulking will assist in preventing this difusion.
Doug questioned the reasoning of keeping the insulation 6"off the floor. Below the frost line the ground remains at a fairly constant temperature. At footing level the heat loss through the foundation wall is not significant. The cost of this energy loss is miniscule compared to the cost & inconveinience of ripping off the drywall to replace soaked insulation from a minor flood. A difference of opinion on methods & proceedure is common place in the construction industry.
 
  #14  
Old 01-16-03, 08:58 PM
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Allen and Brewbeer,

Both of your comments are interesting and yet complex in nature. The issue here is that regardless of all the technology that may be learned and is being learned, homes built 10 + years ago compared to now, the issue is that those in the trades have to keep one BASIC thing in mind at all times...we have to abide by the BUILDING CODES. As such, what Brewbeer brings up has it's valid points but in addition to that, where one lives determines what is considered CODE in that area. I read what was in the BSC site, what is interesting though more is said based upon personal opinion and not applied in todays construction. It's just theory that has not been applied or shall I say not enforced by Building Officials. I guess this is the same here at the forum except that I have to abide by APPLIED SYSTEMS in force today. What they said did make sense in part but as they said, "you have to change the way people think it should be done before they can be used". As such the Building Codes do vary by region in areas concerning insulation, vapor barriers/retarders, air barriers, etc. How a home is built up north is sure different than in a southern state.

With regards to cutting the insulation short 6" from the bottom of a basement wall might make sense in a minor flood, it would not fly with a Building Inspector. I have seen them fail inspections because it was not properly installed and this would be a definite violation. Technically you're right Allen, heat loss would be minimal but then why insulate at all if this was the case? I agree with you "differences of opinion on methods & procedure is common place in the construction industry." Unfortunately, I have to abide by Building Codes and how it effects the home and owner. I have no choice...you do... until you pull a Building Permit.

I really appreciate the comments and insight to different ideas. It's good to learn something new each day or I am not doing my job.

Thanks again to both of you!
 
  #15  
Old 01-16-03, 09:02 PM
KSS
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Ok,

So I started this thread and here she goes.

Option 1
1. I coat the surface of the interior foundation block with a waterproofing material of some sort. any thoughts the surface is painted?
2. I put ridgid insulation glued to the foundation interior wall.
3. I stud it out with 2x4 wood studs
4. I fill the cavity between the studs with roxul insulation
5. I apply my 3/8 drywall, NO vapour barrier!

Otion 2

The same as above but put vapour barrier on the foundation wall and between the drywall and studs.

Which one do you guys think?


KSS
 
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Old 01-16-03, 09:05 PM
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KSS,

Ok, since I am already here, #1. 3/8"? I guess.

How's that?
 
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Old 01-16-03, 09:23 PM
KSS
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#1 is a go 3/8" or 1/2" I guess

Thanks

KSS
 
  #18  
Old 01-16-03, 09:24 PM
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KSS,

Just a note..1/2" is usually the minimum that is required to cover rigid insulation. Needs this to meet fire codes.
 
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Old 01-17-03, 10:03 AM
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Identifying source before preventive measures.

For every action, there is a reaction. Different applications within a confined space will react with each other. Number one source for moisture and humidity in basements is negative pressure asserted on masonry components below grade. An average dry basement will have a negative 2 Pascals. A Pascal is an increment similar to an inch, mile, meter, etc. which is used to measure pressure difference between areas.

For example, a natural draft or atmospheric furnace uses 15 cubic feet of air for combustion and 15 cubic feet for dillution air (air that goes up draft hood) for every 1 cubic feet of gas. Let's assume 1 cubic foot of gas is equal to 1000 BTU's. and the furnace is 100,000 BTU output/hr. for illustration. So 100,000/1000 x (15 +15) = 3000 cubic feet of air consumed in the basement per hour. Since you cannot take air out of the basement without replacing it with the same volume of air, air is suck into the basement from around your window and other places. This exerts negative pressure on the walls about 2 Pascals. Still a dry basement. Your windows are drafty because of the natural draft funace.

But those windows are letting in cold air in the basement. Change the windows to stop the cold air from coming in. This makes it harder to replace the 3000 cubic feet of air and the pressure increases from 2 to 6 Pascals. Best case senario, efflorescence appear on masonry walls and increased humidity levels in basement. Worse case senario, the aforementioned occurs and back drafting. Filling the home with carbon monoxide and everyone dies in the home. Has this ever occurred before, answer, YES.

Understanding that the window are drafty because of the consumption of air by the furnace gives you the possible solutions to avoid the moisture and dangerous conditions. For example, provide a fresh air supply source for the furnace by installing a duct from the outside to the furnace or a vent on an outside wall near the furnace. End result, everyone is the house is safe and the basement stays dry.

To further illustrate how different application react with each other, let's take finishing a basement wall. The problem here is that most people only look at that application and ignore all others. First let's look at the components of the wall concerning moisture. Fiberglass (glass) has a low absorbancy and a fast expulsion rate towards moisture. Wood or metal studs have a higher absorbancy and slower expulsion rate towards moisture than glass. Have anyone ever seen glass rust? Metal does. Masonry has even a higher absorbancy and slower expulsion rate towards moisture than the aforementioned. You have 3 different materials with different rates of absorption and expulsion towards moisture. All 3 in most case touch each other (conductive transfer).

Now we apply heating the basement during the winter in a cold climate to this component. Whenever you heat air, it expands. A pressure area is created about 2 Pascals. But this is positive not negative pressure which means it is pushing outward. Understand that pressure has a greater affect on the water vapor molecule than heat when going through materials. This is because all the materials in the wall have thermal properties. Which means it slows down the heat flow. Does any of the materials slow down the moisture flow as much as it does slows down the heat flow? Answer, NO. A vapor barrier does slow down the moisture flow sufficiently in this application. In other words, you CANNOT apply insulation to a basement wall where you intend to heat this area in a cold climate without a vapor barrier. PERIOD!!! No IFS, BUTS or ANDS. You are not asking for a moisture problem if you don't apply a vapor barrier, YOU WILL HAVE A MOISTURE PROBLEM, if you don't.

But it doesn't stop here. As mentioned earlier you have 3 different materials with different rates of absorption and expulsion towards moisture. An 1 inch gap or dead air space between the wall and the masonry is known as a drainage plane. I will not go into the reason why it's called that, but drainage implies moisture. In simplier terms, it is a buffer that allows a TIME delay for the transfer because of the different rates of absorption and expulsion of moisture between the materials. Sounds familar (vapor barrier).

I did not include other applications like a TV, lighting, washer, dryer and even the occupants, just the things I consider more important. Though combined they are. However, I have never recommended a dehumidifier as a solution to a moisture problem in a basement.
 
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Old 01-17-03, 01:05 PM
KSS
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So your saying I should use a vapour barrier in my option 1 with a layer of poly between the drywall and the studs?

Is that right?

KSS
 
  #21  
Old 01-17-03, 01:46 PM
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KSS,

I'm not, with rigid you don't need a vapor barrier as it is one on it's own. I think resercon was referring to the postings which suggested not using them at all. I agree with resercon that you need it depending on applications. As I noted, option #1 does not need the vapor barrier due to the rigid insulation placed directly against the block. Don't forget the 1/2" drywall.

Hope this helps!
 
 

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