A person called me on the phone with the following problem:
They have moisture inside the wall of their home.
Here is how it is built…
Brick outside.
Plywood next (on the outside of the studs)
Black thick plastic next (under plywood)
Insulation between studs (no paper backing on insualtion)
Sheetrock on the inside of studs.
The moisture problem is between the plastic and the plywood but
some is getting inside the lower part of the insulation.
The wall faces south and they live in Houston Texas (humid area).
What is the cause, and what is the remedy?
Who should they call for advise and repair?
I have some ideas, but I would value your feedback
if you have any input on this problem.
If I’m understanding you, the plastic is being used as a vapor barrier. Since air can’t pass through plastic, moisture builds up in the wall cavities from temperature differentials between the cool air/warm air. The insulation is probable wicking up the moisture and since the wall can’t “breathe”, gravity moves the water down to the lower section of wall.
The best thing about being a home inspector: we don’t have to know the cause or solution. If you don’t know for sure, I wouldn’t be making any guesses. Refer it to a GC.
I will give it to you from exterior to inside drywall.
BRICK VENEER
WEEP HOLES EVERY 4’
1" AIR SPACE
WATERPROOF BUILDING PAPER [UNLESS SHEATHING IS WATER REPELLENT]
SHEATHING [PLYWOOD]
A MOISTURE BARRIER NOT LESS THAN 12" FROM BOTTOM OF STUD WALL. AND IT SHOULD EXTEND UNDER BRICK STARTER COURSE MIN. 1"
WOOD STUDS
INSULATION
DRYWALL
I hope this helps you, I think the problem is that the moisture barrier is under plywood and is trapping the moisture in cavity.
As the moisture is between the plastic in the plywood, this indicates that the moisture is coming from the outdoors (versus condensing from the moist indoor air passing through the sheet rock wall).
Brick veneer siding is not waterproof.
It must be properly installed as to not come in contact with the wood framing of the structure.
Weep hole ventilation is required to allow water which has entered the wall system to escape.
Investigate all other sources of moisture intrusion beginning at the Ridge of the roof, gutters, drip edge, window and door penetrations in the wall etc.
This sounds like a good candidate for thermal imaging evaluation to evaluate the capacity and performance of the insulation barrier. Insufficient insulation may cause the air conditioned air within the house to cool the exterior sheathing of the house and cause condensation from the outdoor air to occur within the wall. This would be my second phase of inspection once I determined rainwater infiltration is not the source.
The solution won’t be easy. Since the plastic is the problem, it has to be removed to establish ventilation. do you know how this client found this problem? did he remove drywall and find the plastic installed as mentioned?
Here is a link to an excellent source for the “Moisture Control Handbook” along with other very good reading material. The handbook will discuss in depth the cladding, sheathing, vapor barier, etc., etc.
This person took the sheetrock off the inner wall and
made the discovery.
Moisture near the bottom of the insulation caused him
to search further and he found the plastic between the
outside of the stud, yet under the plywood, was wet.
The wet side of the plastic was facing to the outside,
touching the plywood.
From everyones comments, it appears that his solution
will not be cheap. This is what I told him also.
The best way my friend, and probably the least expensive. It can also get done while occupants and contents are in the home. No relocation,no hotel room, no storage fee, no moving expenses. I personally think it’s the best way!
</IMG>