Skimcoat in New Hampshire

New Hampshire, United States   

They say it should not be done.

I have chipped off the skim coat that was falling apart after this heavy winter. I was going to seal the cinder block with a excellent Breathable drylock product/paint.

The cinder blocks are in need of a skim coat to fix uneven areas.

The book says that I should use a bonding agent before cement skim coat for proper adhesion. Bonding agents are acrylic and do not breathe.

You say burning wood releases moisture into the brick and the chimney needs to breath.

BUT if I have a pellet stove insert with a metal flue the moisture should have no contact with the brick. 

So can I use a bonding agent so my skim coat does not fall off? 

Are there some other reasons for the need for the chimney to breathe?


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by ChimneyChick | April 07, 2015 ChimneyChick's avatar
Midland, Ontario

Without seeing the project I can only make suggestions on the repair.
If moisture gets trapped in any masonry construction and then freezes, as it changes to ice, it will expand and damage the masonry, THAT is why masonry must be able to breath.
It must be able to release as much moisture as possible to prevent damage.
With the pellet unit venting into a stainless steel liner you will not get moisture from the burn process but you may get interior moisture thru pure condensation between the cold masonry and the warm liner.
I see from you picture that this chimney may have more than one flue channel, what is the other side venting??
Your breatheable drylok paint product may be all you need for an adhesion

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