How do I install a fiberglass shower bay over a concrete floor?

Q I’m ready to frame up the walls for my lower-level bathroom. There’s a 2-in. pipe sticking up through the concrete floor. How do I position my fiberglass shower bay and connect it to the drain?

E. Johanson, via E-mail

A Sounds like your bathroom plumbing is already roughed in, although a call to the plumber or contractor who did the work will confirm it. The 2-in. pipe is typically the shower or tub drain. Line it up exactly with the drain hole in the bottom of your shower bay. This position determines the location of the stud walls around the shower. The supplier may be able to provide a dimensioned drawing of the shower bay, so you don’t actually have to put it in first.

If the existing 2-in. drainpipe isn’t where you want it, you’ll have to break up the concrete and replumb the drain.

Make sure the drainpipe extends at least an inch above the concrete. If the pipe is too short, you’ll have to break up the concrete and extend it. Also, you’ll need at least a 1-1/2 in. space between the pipe and the concrete to accommodate the drain assembly (see photo below). If there isn’t, carefully chisel out the concrete around the pipe.

Tip

If you’re considering a single-piece shower bay, make sure you can get it into the new bathroom space. You may have to bring the unit into the space before framing the doorway or walls. If access is a problem, check out multiple-piece units that will fit through doorways more easily.

How to mount a leakproof drain assembly

After you frame the shower walls to fit the shower bay, lay the bay on its back and install the drain. Use a special leakproof drain assembly called the No-Caulk Shower Drain. It’s available at home centers and plumbing supply houses. Although these drain baskets are available in plastic ($10), I’d opt for the brass one ($18). Follow these steps to attach the shower to the drain:

• Roll out a coil (about the diameter of a pencil) of plumber’s putty (available at all hardware stores) and wrap it under the drain basket flange.

• Hold the drain basket in position in the shower bay drain hole, slide on the washers, and then thread on and hand-tighten the exterior setting ring. Tighten the ring with a large slip-joint pliers until it’s firmly in place. You shouldn’t be able to move the shower basket by hand. The plumber’s putty will squeeze out.

• Lower the shower bay and basket assembly over the drainpipe. Mark the pipe about 3/4 in. below the drain basket flange.

• Lift the shower bay out of the way and cut the drainpipe to length. A hacksaw works well. Make sure to cut the pipe square, not angled.

• Set the shower bay and basket assembly back over the pipe. Slide the caulking gasket over the pipe and push it all the way down so it sits against the lip at the bottom of the drain basket. You may have to tap this gasket into place with a hammer and a thin piece of wood.

• Thread on the caulking nut and firmly tighten to compress the caulking gasket and seal the pipe. Use the slotted bar tool that comes with the drain assembly. Stick the flat blade of a screwdriver into the bar’s slot and firmly hand-tighten.

• Snap on the perforated drain cover (not shown).

Can I install wood plank flooring over concrete?

Q I enjoyed your magazine’s article about solid pine floors (Feb. ’02, p. 28), but my house is built on a concrete slab. What can I do?

Julie Swenson, Atlanta, GA

A It’s considerably more difficult to install a 3/4-in. wood floor over concrete than over a wood subfloor. You’ll first have to install 3/4-in. thick wood underlayment.

The combination of the underlayment and flooring raises the height of the floor 1-1/2 in., so be sure the extra height doesn’t create problems around cabinets, in doorways or at transitions to other types of flooring.

Also, be absolutely sure that the concrete doesn’t get damp because of exterior water problems.

Lay 6-mil polyethylene sheeting over the concrete to minimize moisture migration from the concrete up into the wood flooring. Then fasten 3/4-in. treated plywood to the concrete with concrete screws spaced every 16 in. Alternatively, screwrows of treated 1x4s to the concrete 16 in. on center. Lay the 1x4s perpendicular to the direction you intend to install the floor planks.

Then nail the flooring planks with a standard flooring nailer (see photo for details).

Tip

If the 1-1/2 in. height change is too much, consider laying a laminated wood floor instead. It will add less than 3/4 in. of height. You can either glue it down or float it (the edges are either glued or snapped together). See the article on p. 48.

What size pilot holes?

Q You’re always talking about drilling pilot, clearance and countersink holes when working with wood screws. What size holes do I drill?

A. Charles, via E-mail

A The purpose of the pilot hole is either to reduce the chance of splitting a board or to make a screw easier to drive. In both cases, the hole makes room for the body of the screw shaft, yet leaves enough material for the threads to bite. The drill bit should match the diameter of the screw body (not the threads). In practice, hold the screw up to the light and match a drill bit to the shank diameter.

A clearance hole allows the whole body of the screw to pass through. When it’s important to draw one piece of wood tight to another, first drill a clearance hole.

The countersink allows the screwhead to sit either flush or below the surface. Special drill bits will cut clearance, pilot and countersink holes in one operation. While that’s convenient, you have to buy a bit for each screw size.

What’s the best way to cut off wood door bottoms?

Q I recently installed carpeting and now the doors rub. What’s the best way to trim off the door bottoms without splintering them?

B. Simmons, via E-mail

A Trimming a wood door with a circular saw without splintering the wood or damaging the finish is a challenge. Here’s the method that works best for me.

First mark the clearance needed on the door. Then pull out the hinge pins and lay the door on padded sawhorses.

Mark the cutting line on the top face and edges of the door and apply a 6-in. wide strip of masking tape along the line to protect the door’s finish from the circular saw’s base plate.

Next, score the cutting lines 1/16 in. deep with a utility knife. I like to clamp a metal straightedge to the door on top of the masking tape along the cutting line. This helps to guide the knife, and then if the knife slips,it only scars the waste side of the cut. You don’t need to score the underside of the door.

Make sure your saw blade is sharp and has a minimum of 18 teeth. Hold the circular saw against the edge of the door as if you’re ready to cut. With the blade teeth held just to the waste side of the scored line, mark the masking tape along the opposite edge of the base plate.

Position a straight saw guide at this mark, parallel to the cutting line, and clamp it at both ends. A 3/4-in. thick guide is thin enough to provide clearance under the saw’s motor.

Hold the saw against the cutting guide and check the position of the blade’s teeth. They should be just outside of the scored cutting line. Make the cut slowly. The scored line will stop the splintering. The bottom side of the door won’t splinter because the saw teeth cut up into the wood.

Lightly sand all the edges along the new door bottom to soften them, then rehang the door.

Corrections and additions

Fluorescent ballast reminder

Before you throw out the old ballast from a fluorescent light (Oct. ’02, p. 28), be sure to check for the words “No PCBs.” If the ballast doesn't have these words written on it, return the old ballast to the store or to a hazardous waste site for proper disposal. It may contain PCBs, a chemical mixture that's harmful to the environment.

In addition, if the old ballast was connected with wires that appear to have cloth insulation, replace the entire fixture. Wiring with this type of insulation becomes unsafe as it ages.

Wear goggles

On p. 96 of the Oct. ’02 issue, we showed the proper way to jump a run-down car battery, but the worker hooking up the cables should be wearing safety glasses. Working on or near batteries can be dangerous. When you’re jumping a battery, wear yours.

Art Direction • GREGG WEIGAND

Photography • BILL ZUEHLKE

Consultants • CHARLES AVOLES and LES ZELL, MASTER PLUMBERS