Q: I am putting a new tile shower in my home. The tile is over a steel tub. Unfortunately, I am doing this myself, so I'm really wanting...

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Q: I am putting a new tile shower in my home. The tile is over a steel tub. Unfortunately, I am doing this myself, so I’m really wanting to get this right.

Hearing conflicting information from different sources, I want some advice. Cement backing boards are not waterproof. I want to know whether I should put a plastic vapor barrier beneath the cement board.

It seems to make sense logically, like a last resort to keep water out of the wall. But then others said absolutely do not do this.

Who is right, and why?

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A: You want the tile side of the cement board as watertight as possible, using a trowel-on waterproofing membrane such as Redguard or Laticrete. This type of product (with “tape” at cement board joints) keeps moisture out of the cement board, which is not totally waterproof and also serves as a flexible anti-fracture membrane.

Thinset mortar is applied over the top of the waterproofing membrane after it dries. Interestingly, grout is not waterproof, and cement board is not waterproof, yet they are what is keeping the water out of your wall in a tile shower — which is why waterproofing membrane and grout sealant are so important.

With or without trowel-on waterproofing membrane, a plastic vapor barrier behind the cement board will only hold moisture in the cement board and make the entire assembly prone to mold issues (and by default the wall as well, particularly with some of the non-breathing siding types).

So skip the plastic and save the waterproofing efforts for the wet side of the cement board.

Q: I am moving to the boonies in a couple of weeks and have an almost-new gas dryer that I love and want to keep. The home lacks gas service and has propane, but no connection for the dryer. The previous owner had an electric dryer.

I am sure we could get a gas (propane) pipe to the dryer, since the basement ceiling is open, and the line feeding a fireplace is relatively close.

What would it take to get my gas dryer converted?

A: Welcome to the boonies, friend. A gas line could be installed by a plumber, heating contractor or gas-service company. Generally you are looking at about $400 for a short-line installation, plus a permit. A gas line is not a good DIY project.

All gas-appliance manufacturers make gas/propane conversion kits for their products. The kit is typically less than $20 at appliance dealers, and will at a minimum include a new burner orifice, a sticker indicating it has been converted and instructions.

The conversion itself is fairly simple if you are mechanically inclined, but also could be undertaken by a service technician if you don’t feel qualified after reading the instructions and having a gander.

Q: If my bathroom exhaust fan is vented to the outside but not insulated over its top, can it condense water? I got “rained” on (small little drip-drip-drip action) while sitting in that most sacred place of honor one cold clear morning this past winter and wondered whether condensation could be the reason.

A: Yes, indeed it can. In fact, many municipalities require the pipe leading away from the fan to be insulated as well, since it can produce condensation, run down the pipe and rain on your parade that way, too.

You could insulate your fan and the pipe leading away to the exterior to prevent this.

Darrell Hay is a local home inspector and manages several rental properties. Send questions to dhay@seattletimes.com or call 206-464-8514 to record your question. Sorry, no personal replies.

More columns can be found at www.seattletimes.com/columnists.