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Old 10-18-2013, 12:23 AM   #1
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Duplex on concrete pad with mold since NEW please help.


Hello....any help and thoughts on this would be incredibly appreciated.

I hired a contractor (no longer in business) to build a duplex; two small apartments, ranch style, single floor/story on a concrete pad.

The outer walls only (never the walls on the inside) are molding on the sheetrock inside and it only does it in the winter time, never in the summer. My guess is that in the summer, the windows are open and there isn't the hot/cold meet in the air/walls like there is in the winter.

We tried venting the attic space and building subfloors inside and nothing is working. I've had several contractors look at and give their 2 cents, but none has any real concrete reasons why it's doing it.

The pad was insulated.
There is plastic on the outside of the insulation under the sheetrock.

One contractor suggesting cutting out all of the plastic.

Another contractor suggested putting vented holes throughout the outside.

Another contractor suggested a frost wall around the pad.

We spent way too much on a permanently installed commercial dehumidifier that didn't work either.

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Old 10-18-2013, 01:15 AM   #2
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Duplex on concrete pad with mold since NEW please help.


location many times affects building due to climate. where is it located?

I'm guessing when the mold develops you are doing something in an attempt to remove the mold since you state it only happens in the winter.

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Old 10-18-2013, 01:42 AM   #3
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Duplex on concrete pad with mold since NEW please help.


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location many times affects building due to climate. where is it located?

I'm guessing when the mold develops you are doing something in an attempt to remove the mold since you state it only happens in the winter.
We try to clean it up the best we can with bleach and mold resistant paint.

Any ideas on how to stop it?

Thanks.
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Old 10-18-2013, 06:10 AM   #4
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Duplex on concrete pad with mold since NEW please help.


Is this mold forming at the bottom of the walls, top, or all over? How about the ceiling? Bathrooms worse than other rooms? How do the windows look durring the winter, Lots of condensation? What are the humidity readings during the winter? How much insulation is in the attic, walls, Etc? You say thee is a de-humidifyer, How much water is it pulling out during the winter? Also, we realy should know where you are located. If you live in the desert in Arizona, causes and solutions will differ greatly than if you live, say, in Tacoma Washington.
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Old 10-18-2013, 07:40 AM   #5
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Duplex on concrete pad with mold since NEW please help.


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location many times affects building due to climate. where is it located?
insulation and vapor barrier requirements are based upon the location of the building. Where is the building located?
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Old 10-18-2013, 08:18 AM   #6
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Duplex on concrete pad with mold since NEW please help.


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Is this mold forming at the bottom of the walls, top, or all over? How about the ceiling? Bathrooms worse than other rooms? How do the windows look durring the winter, Lots of condensation? What are the humidity readings during the winter? How much insulation is in the attic, walls, Etc? You say thee is a de-humidifyer, How much water is it pulling out during the winter? Also, we realy should know where you are located. If you live in the desert in Arizona, causes and solutions will differ greatly than if you live, say, in Tacoma Washington.
It's all at the bottom of the walls, but just on the outer walls, meaning, only the part of the walls that are exposed on the outside, but on the inside......hope that's clear as mud.

Nothing on the ceiling whatsover.

Bathroom is the same; nothing on the inside walls, but on the walls that face the outside, it's on the bottom.

Their is normal rolled, R14 I think, insulation that's just laid in the attic and in the walls.

The commercial dehumidifier, which made a hardly noticeable effect is vented outside, so I have no idea of how much water it's been pulling.

The building is in the state of Maine.

Thanks a bunch....looking forward to hearing back any suggestions.
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Old 10-18-2013, 08:19 AM   #7
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insulation and vapor barrier requirements are based upon the location of the building. Where is the building located?
Yup, sorry about that....state of Maine.
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Old 10-18-2013, 09:19 AM   #8
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Duplex on concrete pad with mold since NEW please help.


Insufficient insulation would be the top suspect here. R 14 isn't even code acceptable here in the much warmer South. Were the walls 2x6 construction? It's difficult to cram in the required insulation in a cold climate like Maine any other way. Even then, using XPS on the exterior before siding is a good idea.

You can look for yourself what is required for your particular county here
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Old 10-18-2013, 02:54 PM   #9
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Duplex on concrete pad with mold since NEW please help.


Insulation would also be my suspect. You may need to cut a opening in the bottom of the worst area and make sure the insulation and vapor barrier are clear to the bottom. I think unless you open one wall it will be all guessing, and you will probably need to open it to fix it anyway.
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Old 10-19-2013, 05:01 AM   #10
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Insufficient insulation would be the top suspect here. R 14 isn't even code acceptable here in the much warmer South. Were the walls 2x6 construction? It's difficult to cram in the required insulation in a cold climate like Maine any other way. Even then, using XPS on the exterior before siding is a good idea.

You can look for yourself what is required for your particular county here
I'll go out and check to see what it is exactly....that's just what came to mind....I could be wrong...I'll double check, thanks.

Walls are 2x4.

Outside of the duplex in consists of this: T111, 2x4's with insulation, plastic, then sheetrock.

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Insulation would also be my suspect. You may need to cut a opening in the bottom of the worst area and make sure the insulation and vapor barrier are clear to the bottom. I think unless you open one wall it will be all guessing, and you will probably need to open it to fix it anyway.
We pulled the T111 off on the back side and noticed a small gap from the bottom of the insulation to the pad....that could be the issue...I'm hoping it's something as simple as that as we've spent thousands and thousands of dollars and cannot solve this thing. I'll also check to see how low the plastic goes.

Thanks.
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Old 10-19-2013, 04:35 PM   #11
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Duplex on concrete pad with mold since NEW please help.


There's no sheathing? And only 2x4 construction? You've got some issues there. Fiberglass batt insulation in a 2x4 cavity wall isn't sufficient.
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Old 10-19-2013, 05:14 PM   #12
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Duplex on concrete pad with mold since NEW please help.


Do you know if you have cold drafts coming through these areas in the winter? No sheathing, and if not sealed at bottom, could be the cold outside air blowing through the base of the wall, cooling the drywall enough to cause condensation with the inside air.
Any carpet in there? Do you notice the edges of the carpet near the exterior walls get dirty?
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Old 10-19-2013, 09:35 PM   #13
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Duplex on concrete pad with mold since NEW please help.


I agree. A good read; "Mold and mildew occur on cold surfaces where
the relative humidity is highest, such as those caused by
missing insulation or thermal bridges (local areas that are
poorly insulated). It is typically noted on inside surfaces of
window frames and exterior walls and ceilings." from; http://philipmarshall.net/pdf/tsongas_92_residences.pdf

Could be number of other things as well; no sill sealer between bottom plate/slab; http://www.greenbuildingadvisor.com/...-building-code

Convective looping around/through the low density (R-11) fiberglass batts, pp.43-47; http://www.buildingscienceconsulting...Measure_Up.pdf Note pp.39; R-11 really R-5.5 with framing factor.

Missing/incomplete vapor barrier required for your location- pp. 15-19; Figs. 4a, 5a per location Zone 6 or 7; http://www.buildingscience.com/docum...nd-wall-design

http://energycode.pnl.gov/EnergyCode...sp?state=Maine

Are the outlet boxes sealed? http://www.buildingscience.com/docum...wall-approach/

Is the slab/mudsill joint caulked, below the drywall as said, or a sill sealer? Fig.1; http://www.buildingscience.com/docum...ms?full_view=1

Are there flowerbeds nearby? Fig.6; http://www.buildingscience.com/docum...sture-problems

BTW; T-1-11 is a structural siding, I first installed it in '73 around here.... all the rage for about 10 years...

Air currents in the room usually don't sweep the low areas of exterior walls to remove interior moisture from condensing there, IMO. Check for insulation (as noted)/vb and paint with oil-based there, for a test.

Gary
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Last edited by Gary in WA; 10-19-2013 at 09:38 PM. Reason: Added thoughts.
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Old 10-23-2013, 05:15 AM   #14
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Duplex on concrete pad with mold since NEW please help.


Quote:
Originally Posted by SPS-1 View Post
Do you know if you have cold drafts coming through these areas in the winter? No sheathing, and if not sealed at bottom, could be the cold outside air blowing through the base of the wall, cooling the drywall enough to cause condensation with the inside air.
Any carpet in there? Do you notice the edges of the carpet near the exterior walls get dirty?
There are no cold drafts coming in that we can tell.

We thought it was the bottom opening as well and put some blown in spray foam underneath and it made no difference.

There is carpet and I don't notice any dirt but mold, yes.

Quote:
Originally Posted by Gary in WA View Post
I agree. A good read; "Mold and mildew occur on cold surfaces where
the relative humidity is highest, such as those caused by
missing insulation or thermal bridges (local areas that are
poorly insulated). It is typically noted on inside surfaces of
window frames and exterior walls and ceilings." from; http://philipmarshall.net/pdf/tsongas_92_residences.pdf

Could be number of other things as well; no sill sealer between bottom plate/slab; http://www.greenbuildingadvisor.com/...-building-code

Convective looping around/through the low density (R-11) fiberglass batts, pp.43-47; http://www.buildingscienceconsulting...Measure_Up.pdf Note pp.39; R-11 really R-5.5 with framing factor.

Missing/incomplete vapor barrier required for your location- pp. 15-19; Figs. 4a, 5a per location Zone 6 or 7; http://www.buildingscience.com/docum...nd-wall-design

http://energycode.pnl.gov/EnergyCode...sp?state=Maine

Are the outlet boxes sealed? http://www.buildingscience.com/docum...wall-approach/

Is the slab/mudsill joint caulked, below the drywall as said, or a sill sealer? Fig.1; http://www.buildingscience.com/docum...ms?full_view=1

Are there flowerbeds nearby? Fig.6; http://www.buildingscience.com/docum...sture-problems

BTW; T-1-11 is a structural siding, I first installed it in '73 around here.... all the rage for about 10 years...

Air currents in the room usually don't sweep the low areas of exterior walls to remove interior moisture from condensing there, IMO. Check for insulation (as noted)/vb and paint with oil-based there, for a test.

Gary
WOW....tons of information here....it appears the building wasn't built properly.....going to need to spend some time on these sites....THANK YOU VERY MUCH.

THANK YOU ALL FOR THE INPUT.....the information I found here, I'll go over, research, and approach a reputable and knowledgeable contractor to see what the next viable step is.
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Old 10-25-2013, 09:53 PM   #15
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Duplex on concrete pad with mold since NEW please help.


Those are only suggestions to check as we are not "on site". You're welcome, we are here to help!

Gary

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