Propping Up Sagging Floors a Major Project

QUESTION: We’ve just bought a 50-year-old house. Not surprisingly, the floors are sagging. How big a job would it be to straighten them out, or should I just forget it? Structurally, everything seems to be in good shape.

ANSWER: In older houses, built before lumber was graded for strength, sagging floors were a common problem. Fixing them is hard work, but it is a possible project for the ambitious remodeler.

First, determine how much sag or deflection you have. This can be measured while a helper holds a straightedge that spans the floor from wall to wall. Or measure the distance from the basement floor to the bottom edge of the floor joist, both where the ends of the joist rest on a center wall or support beam and at the center, where the sag is greatest.

To straighten the floor, you’ll need a helper or two, a scissors jack or hydraulic jack, extra joists the same size and length as existing joists, a 4-by-4 long enough to reach from the top of the jack to the bottom edge of the joists, a supply of 16d nails, a hammer and a ruler.

Set the jack under the center joist, at the center of the room. Measure and cut the 4-by-4 post so it reaches from atop the jack to the bottom edge of the joist. Now, working carefully, and being sure that the 4-by-4 post is exactly plumb, use the jack to raise the post and jack the sagged joist until it is level. Depending on the amount of sag you have, you may want to do this in stages and use temporary props to prop each floor joist until they are all raised, then complete the job in a second stage.

When the joist is level, set a new joist alongside the old joist. The ends of the new joists must be settling atop the foundation on one side and the support beam or wall on the other side. While the jack holds the old joist straight, drive the 16d nails through the new joist and into the old one. Nail the two doubled joists together at 16-inch intervals. Remove the jack and make sure the joists are straight.

Gloss Can Clean Most Fiberglass Showers

Q: My fiberglass shower enclosure has become dull and film-coated. I’ve been told not to use an abrasive cleaner. What do you suggest?

A: Abrasive cleaners or cleaning pads can leave fiberglass finishes with scratches, difficult or impossible to repair. We’ve had good luck with a cleaning product called Gel-Gloss, available at most supermarkets. Once it’s clean, you can make the fiberglass easier to clean and more stain-resistant with an application of automotive-type wax or polish. Bear in mind, however, that the floors of shower base units or the bathtub bottom may become slippery if waxed, so wax only the surfaces you do not walk or stand on.

If mineral buildup is heavy, consider doing something about your water quality. Water treatment experts can install filters in water lines to remove lime, rust or other potential sources of stains. Installing a water softener will usually end stains from most water-borne minerals. If soap scum is the problem, soft water will leave less soap residue. Also, consider using an alternative brand of soap that may produce less soap film buildup.

Haywire Dishwasher May Have Cracked Arm

Q: My Maytag dishwasher has a curious problem. When the machine was about 3 years old, the water pump failed, and I replaced it with another Maytag pump. The dishwasher then worked perfectly for about 6 months. Then the force of the water began flipping over the drinking glasses on the bottom rack, breaking nearly two dozen of them. Both the upper and lower spray arms are spinning freely and the water outlet holes are not clogged. Any clues?

A: This problem may be with the lower wash arm, made of polypropylene plastic. When the wash arm has developed a crack or split, all the water under pressure that comes into the arm doesn’t pass through the holes in the arm as it should. The water finds its way to the crack, enlarges it and squirts out in all directions.

This causes strange things to happen inside the dishwasher, including the flipping of glasses. We suggest that you remove the lower wash arm and inspect it carefully. Look for a hairline crack, particularly along the top of the spray arm. A replacement wash arm is available for about $20 from your Maytag parts distributor.

Crayon on Walls: Scrub It Off or Seal It In

Q: My 4-year-old son decided to use the living room wall as a canvas for his new crayon set. I’ve had problems in the past trying to paint over stains when I was unable to completely remove them. What’s the best procedure for dealing with this problem?

A: Your first impulse may be to try to paint over the stain, but many stains cannot be covered with paint alone. Rust, grease and oil, crayon wax and Magic Marker ink may be activated by the solvent (water or oil) in the paint and bleed back through the new paint.This is true regardless of how many coats of paint you apply. You must either seal over the stain or remove the offending material from the wall before painting.

The best approach is to try to remove the stain material. Check with your local paint dealer for products containing solvents that will remove splattered latex paint, grease, crayon and other stains. Pour some cleaner on a clean cloth, wet the stain and let the cleaner work for a couple of minutes. If you just try to scrub the stain away, you may also remove some wall paint.

If the stain comes off the paint, spot prime the stain area and then repaint the wall.

If the stain proves difficult to remove, you can seal in almost any stain with a shellac sealer. The shellac is fast-drying so it does not activate the stain material, covering it over instead.

To avoid the shiny spots caused by higher sheen over the shellac sealer, seal the entire wall with shellac, not just the stain.

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To submit a question, write to Popular Mechanics, Reader Service Bureau, 224 W. 57th St., New York, NY 10019. The most interesting questions will be answered in a future column.