spraying cinder block | Ask Mason Knowles - SPF Consultant | Spray Foam Technical Questions and Answers | SprayFoam Magazine Q&A Forums

Q&A Forums

Author	Comments
thomas malloy Posted: Jul 23, 2009 08:46 AM	spraying cinder block i have a client that wants me to spray his basement from the interior and his wall is made of cinder block (conrete) when it rains the cinder block tends to get wet on the inside but it drys out after a few days. what happens when i spray the block when its dry and then it rains he wants to know how is the block going to dry itself out now that it is sprayed. is there any precautions i should take before spraying cinder block walls. beside making sure there are no cracks and that the substrate is dry and free of dirt or any substance that will affect adhesion.
mason Posted: Jul 23, 2009 09:13 AM	He has a legitimate concern. You need to find the source of the leaks before insulating the block. Even if you don't insulate the block, your client should investigate its source. There are companies that specialize in this type of work. Have him get an inspection and recommendation before installing any foam to the inside. Because the block has cavities within it if any water gets into the block, it cannot dry towards the inside after you spray the foam. This would similar to a sprayfoam roofer plugging up the weepholes in a brick parapet wall. One question, does water actually come out of the block and accumulate on the floor of the basement?
Dennis Davidson Posted: Jul 23, 2009 10:06 AM	Mason I just went through this same situation about 2 months ago. I told the home owner to get a professional to inspect the exterior of the wall. They ended up digging one entire side of the foundation down to the footer. They found two 1/4" cracks at each corner of the foundation that was not visible from the inside. It was repaired and sealed and new insulation installed on the exterior of the block. If it would have been sealed with foam on the interior, water would have been trapped within the block.
Posted: Jul 26, 2009 08:33 PM	..hold on there bubbalooie,,, you say you can stop leaks on a roof by spraying from the inside of the building,,,but,, you say you cant stop the weeping block foundation???? your right,,you cant stop leaks from the inside,,water isa****** and hydrostatic pressure will prevail.... the block wall will dry as it is drying now,,,except,,it wont dry to the inside of the building after the foam application,,well not as much vapor or gross water drive to the interior,,so the wall will dry back to the outside as the "watertable" subsides,, many of these folks already know the verdict,,excavate,,,tile and get the water away from the foundation,,and the price and the process freaks them out so they are lookin for some other "easier" alternative,,be careful what you represent you can do,,,if it leaks before foam,,it will leak after foam,,, ps: you will reduce the gross & vapor drive,,,but man,,be careful about "what you gaurantee"....
mason Posted: Jul 27, 2009 07:29 AM	Foamdude, These are different scenarios. In a block wall, there is a cavity within the block that can hold water. Sealing up the inside would not allow the water to drain out and it would just accumulate. If it was a masonary wall with no cavities within it, the foam might just seal the wall sufficiently to work. (you would have to consider the hydrostatic pressure, so how high the water table would be a factor.). Plus in that case you would see a crack and could repair it before installing the foam. When spraying the foam to the underside of the roof deck, you again have a layer of roof decking with gaps and cracks between the boards. The foam goes into the gaps and cracks making the roof sheathing a single piece, thereby stopping leaks from getting through the roof deck. The water stays on top of the deck and then gravity takes it to the edge. The only place water could get into the roof is at penetrations through the roof such as vent pipes, etc. If the flashing is deficient, leaks can occur just like any other roofing system and the water will come through just like any other roof system.
Posted: Jul 27, 2009 08:16 AM	mason,,luv you man,,, come visit my small shop,,, 'dude ps: tapeing seams and caulking fasteners and coating late this week me hopes,,,wish i knew a good roofer...lol

Author

Comments

thomas malloy

Posted: Jul 23, 2009 08:46 AM

spraying cinder block

i have a client that wants me to spray his basement from the interior and his wall is made of cinder block (conrete) when it rains the cinder block tends to get wet on the inside but it drys out after a few days. what happens when i spray the block when its dry and then it rains he wants to know how is the block going to dry itself out now that it is sprayed. is there any precautions i should take before spraying cinder block walls. beside making sure there are no cracks and that the substrate is dry and free of dirt or any substance that will affect adhesion.

mason

Posted: Jul 23, 2009 09:13 AM

He has a legitimate concern. You need to find the source of the leaks before insulating the block. Even if you don't insulate the block, your client should investigate its source. There are companies that specialize in this type of work. Have him get an inspection and recommendation before installing any foam to the inside. Because the block has cavities within it if any water gets into the block, it cannot dry towards the inside after you spray the foam.

This would similar to a sprayfoam roofer plugging up the weepholes in a brick parapet wall.

One question, does water actually come out of the block and accumulate on the floor of the basement?

Dennis Davidson

Posted: Jul 23, 2009 10:06 AM

Mason
I just went through this same situation about 2 months ago. I told the home owner to get a professional to inspect the exterior of the wall. They ended up digging one entire side of the foundation down to the footer. They found two 1/4" cracks at each corner of the foundation that was not visible from the inside. It was repaired and sealed and new insulation installed on the exterior of the block. If it would have been sealed with foam on the interior, water would have been trapped within the block.

Posted: Jul 26, 2009 08:33 PM

..hold on there bubbalooie,,,
you say you can stop leaks on a roof by spraying from the inside of the building,,,but,,
you say you cant stop the weeping block foundation???? your right,,you cant stop leaks from the inside,,water isa****** and hydrostatic pressure will prevail....

the block wall will dry as it is drying now,,,except,,it wont dry to the inside of the building after the foam application,,well not as much vapor or gross water drive to the interior,,so the wall will dry back to the outside as the "watertable" subsides,,

many of these folks already know the verdict,,excavate,,,tile and get the water away from the foundation,,and the price and the process freaks them out so they are lookin for some other "easier" alternative,,be careful what you represent you can do,,,if it leaks before foam,,it will leak after foam,,,

ps: you will reduce the gross & vapor drive,,,but man,,be careful about "what you gaurantee"....

mason

Posted: Jul 27, 2009 07:29 AM

Foamdude,

These are different scenarios. In a block wall, there is a cavity within the block that can hold water. Sealing up the inside would not allow the water to drain out and it would just accumulate. If it was a masonary wall with no cavities within it, the foam might just seal the wall sufficiently to work. (you would have to consider the hydrostatic pressure, so how high the water table would be a factor.). Plus in that case you would see a crack and could repair it before installing the foam.

When spraying the foam to the underside of the roof deck, you again have a layer of roof decking with gaps and cracks between the boards. The foam goes into the gaps and cracks making the roof sheathing a single piece, thereby stopping leaks from getting through the roof deck. The water stays on top of the deck and then gravity takes it to the edge. The only place water could get into the roof is at penetrations through the roof such as vent pipes, etc. If the flashing is deficient, leaks can occur just like any other roofing system and the water will come through just like any other roof system.

Posted: Jul 27, 2009 08:16 AM

mason,,luv you man,,,
come visit my small shop,,,
'dude

ps: tapeing seams and caulking fasteners and coating late this week me hopes,,,wish i knew a good roofer...lol

You need to login to reply to this topic. Please click here to login.