Ask Handyman

By Travis Larson

From The Family Handyman

How should I install cement board on a floor?

Q I’m getting ready to replace the loose, cracked ceramic tile on my bathroom floor. I pulled a few tiles free and saw that the tile was glued down to plywood. I know that I should use cement (backer) board for the new tile and would like some information on installing it correctly.

Pat Mulcahy, San Diego, CA

A You’re right—cement board is the right choice for your tile base. No matter what you’re told at the store, it’s not a good idea to install tile directly over plywood, especially in a damp area like a bathroom. Because plywood expands and contracts beneath the ceramic tile, grout and tile failure (loose tiles and cracked, crumbling grout) is just a matter of time. Correctly installed cement board provides a very stable base that’s permanently bound to the tile with thin-set mortar so your new tile floor will last a very long time. “Correctly installed” is the key.

Here are the steps to a sound ceramic floor:

Prepare a solid, squeak-free subfloor

One of the keys to a long-lasting tile installation is the underlying subfloor. It has to be rock solid before you lay the 1/2-in. thick cement board. Whatever your subfloor is made of, be sure it’s squeak free before you install the cement board. Screwing the plywood down to the floor joists should take care of most squeaks.

To determine your subfloor construction, pull off a heating grate and look at the exposed subfloor edges. Here’s how to prepare the most common subfloor types:

• 1/2-in. plywood with 5/8-in. particleboard underlayment. Remove the particleboard and screw the plywood to the floor joists with 1-5/8 in. drywall screws spaced every 6 in. Install a layer of 5/8-in. CDX plywood and screw it to the subfloor with 1-5/8 in. drywall screws spaced every 4 in.

• 3/4-in. tongue-and-groove plywood or OSB (oriented strand board). No extra layers of underlayment are required. Just screw the floor down with 1-5/8 in. drywall screws spaced every 6 in.

• Vinyl flooring glued over 1/4-in. underlayment. As long as the subfloor is 3/4-in. tongue-and-groove material, screw the underlayment down right through the vinyl with 1-1/4 in. drywall screws spaced every 6 in. Use 1/4-in. thick cement board instead of the usual 1/2-in. sheets. That’ll keep the floor thickness to a minimum.

Get rid of the high ridges and sink the fasteners

Check all plywood seams with a straightedge held perpendicular to the seams. If it teeter-totters over any joints, use a belt sander to grind down the ridge so it’s even with the rest of the floor. Set any “proud” nail- or screwheads.

Embed the cement board in latex-modified thin-set mortar

The main reason for using thin-set between the cement board and the subfloor isn’t as much for bonding as it is for even, void-free cement board support throughout the floor. Precut and fit all the cement board and lift it out. Then spread thinset mortar with the flat side of a 1/4-in.notched trowel and use the notched edge to “comb” the mortar.

Embed the cement board and screw it to the underlayment

with special 1-1/4 in. cement board screws spaced every 4 in.

Tape the seams

Lay cement board fiberglass mesh tape over all the seams (it’s sticky on one side). Use a wide putty knife or a flat trowel to spread thin-set mortar over the tape, making sure to knock down any ridges or high spots.

Lay the tile in thin-set

Set the tiles using the same latex-modified thin-set and techniques used for the cement board. Only mix as much thin-set as you can use in a half hour and be sure to have solid support under each tile. If you follow all these steps, you’ll have a stiff, monolithic, crack-free floor.

What’s the best way to reinforce concrete?

Q I’m pouring a concrete patio slab and am wondering how I should reinforce the concrete. Is the new fiber-reinforced concrete an OK substitute for the welded wire mesh that’s been around for years? I want to do the job right so my slab lasts.

Howard Wolfe, Flint, MI

A The real question is whether or not you even need reinforcement. It really isn’t required on a slab that just gets foot traffic. For slabs that get automobile traffic, reinforcing rod (often called rebar) is a better way to buttress the concrete than fiber or welded wire.

Concrete cracks will develop. The best you can hope for is to direct them with purposely placed “control” joints tooled into the slab. The joints should be at least one-fourth the thickness of the slab. For sidewalks, the control joints should be placed as far apart as the sidewalk is wide (for example, space joints 4 ft. apart for a 4-ft. wide sidewalk). For slabs, multiply the thickness by 24 to get a rough idea of the spacing. Then divide the slab equally within a range of 8 to 12 ft. (For example, a 4-in. thick slab times 24 in. equals 96-in., or 8-ft., spacing between joints.)

To prevent cracks in a typical patio, you just need to follow a few simple guidelines while ordering, pouring and curing the new slab. That’s much more important than using any reinforcement.

For your best shot at a crack-free slab, follow these tips:

• If possible, pour concrete on a cool, windless, cloudy day.

• Order at least 3,500-psi concrete and don’t ask the operator to add any extra water to the mix.

• Order “air-entrained” concrete, especially important because you live in a region that freezes.

• If you have poor-draining soil under the slab, remove 4 in. of earth and replace it with well-compacted gravel.

• After the slab hardens overnight, keep it moist for at least three days by occasionally running a misting-type sprinkler over it.

Are you really safe? GFCI protection

Q I’m not sure if my receptacles are the GFCI-protected kind. Can you explain how to find out?

Bill Boyer, Philadelphia, PA

A A GFCI-protected receptacle can be one of two types: It can be the type with GFCI circuitry built into it, easily identified by a test and reset button on its face, or it could be a standard receptacle wired to a remote GFCI receptacle or a GFCI circuit breaker in the main panel. GFCI receptacles should be labeled (see photo) but aren’t always.

The easiest way to check is by using a GFCI Receptacle Tester ($12 to $15). Plug it into the questionable receptacle and push the test button. The remote GFCI, if present, will trip and the tester’s lights will go out. If this occurs, find the remote GFCI and reset it. Sometimes the remote GFCI you have to reset is a GFCI circuit breaker in the main panel. Then label the receptacle on the faceplate as GFCI protected.

Plans for PVC patio furniture

Q In a previous “Ask Handyman” answer (Dec./Jan. ’01, p. 8), you said that people make cool stuff out of PVC pipe, such as lawn furniture. Are there plans available for making lawn furniture with PVC piping and fittings? I’m particularly interested in a pattern for a chaise lounge.

Mrs. Ted Luecht, Nekoosa, WI

A A company called PTG (Patios To Go) Plastics sells supplies for PVC furniture and has free plans available on its Web site. Some of the plans are complex and require heat bending, but even a beginner can handle others.

The PVC pipe offered at home centers for plumbing isn’t the best to use for furniture because it’s brittle, ugly and can’t stand up to the sun. Specially formulated, furniture-grade PVC fittings and piping are worth investing in for long-lasting furniture. They’re sleeker, colorfast (in white, beige and gray), impact resistant and UV resistant, and they have no unsightly printing or stampings.

You can visit PTG’s Web site at www.patiostogo.com or call (352) 243-3220. The company is located at 307 N. Hwy. 27, Clermont, FL 34711.

Circular saw recall

Ryobi Technologies Inc. has announced a recall to repair the following circular saws: model numbers CSB120, CSB130, CSB1308, CSB130K and CSB130JS. The model number is on a white label on the motor housing. These saws were sold from October 1998 through July 2001.

The lower blade guards can stick in the open position, posing a risk of serious injury. If you own one of these saws, stop using it and call Ryobi’s Consumer Response Team for a free repair kit at (800) 867-9624 between 8 a.m. and 5 p.m. ET Monday through Friday or log on to the company’s Web site at www.ryobitools.com.

Consumers also can write to the company at: Ryobi Technologies Inc., P.O. Box 1207, Anderson, SC 29622, Attention: Consumer Response Team.

Art Direction • GREGG WEIGAND

Photography • BILL ZUEHLKE