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Handyman on Call

Is there a way to seal a damp brick floor?

Q. Our master bedroom was originally an outdoor carport that was enclosed. The floor of the carport is brick. These are full bricks (not pavers) and are not sealed. There was new carpet laid over that brick. We had horrible issues with moisture coming up through the brick and molding the carpet. We ripped out the carpet and are stuck as to how to proceed. There is no moisture barrier between the concrete slab and the brick, as it was not originally intended to be an indoor space. We have left the brick exposed for about two months to let it “air out.” However, when we put down one small area rug, mold formed under it in just a week’s time. Many of the bricks around the edges are so wet they crumble when poked with something sharp.

One flooring expert advised that we should not seal the brick and cover it with a no-glaze ceramic tile with a large (¼-inch) grout so that the floor can breathe. But another expert said the glue for the tile would never properly dry and we would likely have tiles popping up and grout cracking. Another advised against sealing the brick because the moisture will likely spread to the outer edges and destroy baseboards and Sheetrock. He said moisture will eventually form under the seal, causing a whitish/cloudy appearance on the brick surface. Yet another expert suggested we do seal the brick and then lay a “floating” laminate floor such as a wood laminate that has pieces that lock into place.

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The best option would be to remove the brick flooring and start from scratch by preparing the subfloor properly. But this is a very expensive option and one that will have us out of our bedroom for a long time. Do you have suggestions?

STACEY RASE

A. All those experts listed the correct problems of the inability to stop the rising damp (an English term for water vapor rising from the ground and through slab and brick). But their solutions will not work. You wisely checked again by placing a small rug on the brick, which confirmed the rising damp. Your describing the brick crumbling from a sharp blow when wet made me believe the bricks are very old and soft in the first place.

If you ever want to enjoy that room, you have to do what you said is a very expensive option. And that is to pick up the bricks and use them for another purpose. If the slab is intact, put down 6-mil polyethylene as a vapor barrier, with a foot or so going up walls). Then pour a 4-inch slab and install large ceramic tiles with thin-set mortar. You can put down area rugs if you like. If everything works as it’s supposed to, you will get no moisture coming up from the ground.

Q. I have black slate around my fireplace, but it’s dull. Is there any way to make it shine?

STEVE, in Hotton’s chat room

A. You’re maybe too young to remember blackboards, which were slate in my time, long ago. They were black, and had no shine, so be content it’s the way slate is supposed to look.

If you want it to shine, paint the slate with a clear sealer.

Globe Handyman on Call Peter Hotton also appears in the Sunday Real Estate section.
He is available 1-6 p.m. Tuesdays to answer questions. Call 617-929-2930. Hotton (photton@globe.com) also chats online
2-3 p.m. Thursdays. Go to www.boston.com.
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