For a Secure Steam Room, Sweat the Small Stuff

Q: DEAR TIM: I have wanted a steam room in my house for a long time. Are there certain things you must do to ensure that a home steam room will work well? How do you build a steam room that doesn't have any water or water-vapor issues? -- Nate B., Lexington, Ky.

A: DEAR NATE: When I was a kid, my friends and I would go swimming at an indoor health facility. It had a steam room that was wonderful to sit in after swimming in the cool pool. Although I have built home steam rooms for more than one client, I have never indulged myself. My aching bones and muscles have complained about this oversight on more than one occasion.

As you get ready to build, don't let the benefits of a steam room distract you. Construction details must be kept in mind to make sure the room doesn't become a haven for mold, mildew and wood rot. Steam and wood do not play well together. If possible, all wood framing for your new steam room should be treated lumber, including the subfloor.

Steam will readily return to the liquid state by condensing on cooler surfaces. Because the steam is so hot, the vapor will condense even on surfaces that are warm to the touch. That's what happens when you get out of a hot shower and see a fogged mirror. Don't think for a moment that the fog is only on the mirror; it's on the walls, ceiling and even the wood cabinets in your bathroom.

To build a great steam room, you need to keep the water vapor inside the room, where it can condense and run down to the floor drain. Any steam that does leave the room must be vacuumed out and vented through the roof. If possible, try to make sure none of the steam room's walls is an exterior wall. If any of the water vapor escapes into the exterior wall, you will have serious water issues.

I recommend that you consider ceramic tile for the entire room, including the floor. The tile must be applied to cement board or other substrate approved for use in a steam room. Use thinset mortar to apply the tile to the cement board.

You can use a membrane shower-pan liner that connects to the floor drain to capture all of the water. This is the first thing that needs to be installed after the walls are framed, and it needs to lap up onto the walls by about six inches.

The second-most-important element is a high-performance vapor barrier. You will need to get one that meets the ASTM E 1745 standard. This will protect the wood in your home if you install one giant piece of it on the ceiling and walls without any seams. This vapor barrier must extend over the membrane shower liner. The barrier on the ceiling and walls will capture any water, returning it to the floor drain.

Before you start, I urge you to research in great detail the steam-generation machine. The manufacturers of these heaters have very specific installation instructions that ensure that the units will generate the amount of steam needed. The steam room must be sized correctly for the steam unit you purchase.

The ceiling height in the steam room should not exceed eight feet. It is a good idea to slope the ceiling so that condensation drops do not fall on you as you sit and enjoy the steam. A slope of two inches per foot should suffice.

Tim Carter can be contacted via his Web site, http://www.askthebuilder.com/printer_Submit_Question.shtml.

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