Forums > Specific Focus > Home, Garden & Construction in Mexico

salto_jorge

Nov 2, 2010, 8:01 AM

Post #1 of 10 (3052 views)

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Concrete block Walls, moisture and mold

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Does water leak through concrete block walls causing the plaster to get damp and moldy ?

Do concrete blocks absorb and retain water ? If it can, how can you dry it out ? Will the blocks lose their strength ?

We have a house in GDL that was built in the corner of a lot adjoining another wall.
Can water soak from one wall into our wall and cause issues ?

Do yeso walls that have moisture have to be scrapped off or can they be patched ?

Thank You

Salto

Rolly / Moderator

Nov 2, 2010, 8:47 AM

Post #2 of 10 (3043 views)

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Re: [salto_jorge] Concrete block Walls, moisture and mold

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Typical masonry construction (blocks, bricks or concrete) will allow the migration of moisture if the wall is not properly sealed.
A small amount of migrating moisture in the plaster will create a white discoloration on the paint. It may also peal the paint. This is usually the first sign of trouble. If the plaster is visibly damaged by moisture, the damaged area will need to be removed. There is not much point in re-painting or re-plastering until the wall has been properly sealed, or the source of the moisture eliminated.
Be sure the wall is completely dry before sealing, plastering or painting.

If mold is present, the entire area will need to be striped. Black mold can be deadly, so be careful, use a respirator and gloves when removing the moldy plaster. It is really a job best left to experts.

Rolly Pirate

(This post was edited by Rolly on Nov 2, 2010, 8:51 AM)

morgaine7

Nov 2, 2010, 9:16 AM

Post #3 of 10 (3034 views)

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Re: [salto_jorge] Concrete block Walls, moisture and mold

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Two of my neighbors have a shared wall (property was subdivided) and suffer from the same problem. Not only can moisture travel through the walls, it can also be "wicked" up from the ground. In that case it can be difficult to isolate the source.

I bought an old house, and during the remodeling process, the walls had to be stripped to the bricks and sealed to about 60 cm high. Even then, I've had to have a couple of small spots redone.

Kate

salto_jorge

Nov 2, 2010, 9:30 AM

Post #4 of 10 (3032 views)

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Re: [Rolly] Concrete block Walls, moisture and mold

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The builder has a contractor working on the interior wall today/right now, under a one year warranty and they refuse to strip all the plaster/yeso off the wall and are patching it.

Also to my surprise the contractor insists that the wall does not need to dried out and they sealed the outside of the wall at my neighbors place, something that I did not know. From the roof looking down their wall, it looks like some did a lot of work on it.

I agree with you that the plaster/yeso should be removed.

Rolly / Moderator

Nov 2, 2010, 9:39 AM

Post #5 of 10 (3029 views)

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Re: [salto_jorge] Concrete block Walls, moisture and mold

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It's usually not necessary to strip the entire wall unless it needs to sealed.
If the contractor has solved the problem on the other side of the wall, patching is probably OK
If the wall is not DRY, you probably will have paint pealing problems.
Been there, done that.

Rolly Pirate

salto_jorge

Nov 2, 2010, 10:47 AM

Post #6 of 10 (3022 views)

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Re: [Rolly] Concrete block Walls, moisture and mold

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How long could it take for the wall to dry out if the outside had been sealed as the contractor told us ?

I believe that they worked on the wall other side of the double all in the neighbors place about 2 months ago.

Then about a month ago I had the roof sealed with thermotek blue to make sure water was not getting through the roof and inside of the wall extension (Top Wall) to the wall in the house.

Rolly / Moderator

Nov 2, 2010, 11:16 AM

Post #7 of 10 (3015 views)

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Re: [salto_jorge] Concrete block Walls, moisture and mold

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How long? Hard to say because there are variables -- How wet was the wall? What is the relative humidity where you live.

I live on the desert with very low RH, so a not very wet wall would easily dry in a month.
But in a high humidity place, say near the ocean, it could take longer.

Rolly Pirate

Bennie García

Nov 2, 2010, 2:01 PM

Post #8 of 10 (2997 views)

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Re: [salto_jorge] Concrete block Walls, moisture and mold

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The first thing that needs to be done is finding the source of the moisture. Unless you know where it is coming from there is no point in sealing the wall's surfaces. If they still contain moisture you are just sealing it giving it more time to degrade the stucco. Typically the water is wicking up from below and will continue to do so unless you are able to eliminate the source. I have seen countless cases where stucco in sealed walls will continue to crumble. You need to keep the moisture from getting into the masonry in the first place.

A clear example is when you seal your roof. You know where the water is coming from, rain. You wouldn't seal the interior ceiling. You seal the roof's exterior surface exposed to the rain to keep the water from penetrating.

If I understand correctly your wall is butting up against the neighbors. This presents a common problem where the rain is allowed to get between the walls. And in this case you don't want to seal the interior side of the wall until the moisture is gone and even then I wouldn't recommend it. You need to seal off the crack between the walls to keep the water from running down between them.

And it is highly doubtful your walls are plastered with yeso which is basically plaster of paris or a gypsum based material. This material has very little resistance to moisture. The are more than likely stuccoed with a cement, lime and sand mixture.

salto_jorge

Nov 2, 2010, 3:05 PM

Post #9 of 10 (2988 views)

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Re: [Bennie García] Concrete block Walls, moisture and mold

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All information and ideas are appreciated.

The inside walls of the home are plaster/yeso, the ceiling of the launday room is not, looks like masonary cement.

The home is two stories with a flat roof and shell / structure mostly concrete, rebar and concrete blocks.

The front of the home has rocks cemented to the concrete block walls as does the back, the sides are connected to other structures.

The top of the structures where the walls contact each other are sealed.

Right now I must assume that water was coming from through from the neighbors side that is not part of the coto.

The house does not have any stucco inside or outside, its more of a townhouse in a coto.

mexliving

Nov 14, 2010, 8:22 PM

Post #10 of 10 (2881 views)

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Re: [salto_jorge] Concrete block Walls, moisture and mold

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your home is missing an water sealant.. normally it costs 950.00 pesos for a 5 gallon bucket so its simply not done by some builders.. or the money is given for the worker to purchase and apply and it never makes its way.

your outside walls should have the sealant on the walls prior to painting....... some builders will simply mix a little sealant with paint that does not last for a very long time.