Soap and Sanding Help Paint Stick to Concrete
QUESTION: How can I get paint to stick to the high-traffic areas on our concrete front porch?
ANSWER: Epoxy, polyurethane and acrylic paints wear much better than oil and alkyd paints on concrete. Before applying a water-resistant paint, clean and roughen the surface. Use a trisodium phosphate solution or strong detergent to scrub the floor.
Sanding with coarse emery paper may be required to give the old surface a rough texture for good paint bonding. Test-paint a small area to make sure the new paint will adhere.
Check Out Plywood Before Reroofing
Q: My 25-year-old house needs reroofing and I plan to do the job myself. I would like to lay new shingles over the old ones. However, the builder apparently skimped on the roof sheathing. Instead of the usual one-half-inch thick exterior grade plywood, he used three-eighth-inch sheets. Also, he nailed the shingles directly to the sheathing without putting down a layer of building paper.
Can I add a second layer of shingles? Or would this be too heavy for the three-eighth-inch plywood, considering there can be a foot of snow on the roof in the winter?
A: The builder didn’t necessarily skimp on the roof sheathing. The required thickness depends on the rafter spacing, the grade of the plywood and the direction of its face grain.
Look for the APA stamp of the American Plywood Assn. on the exposed underside of the plywood for the identification index. The index contains two numbers such as 20-0 or 32-16.
The left-hand number represents the maximum recommended spacing in inches between rafters when the face grain of the panel runs at right angles to the rafters. If the rafter spacing is not greater than 24 inches, your sheathing is adequate.
It would be sensible to check with your local building department about a second layer. If your town allows only one layer, you’ll have to tear off the existing shingles.
The builder did skimp on building paper. The paper serves as a backup water barrier between the shingles and the sheathing if shingles are lifted, damaged or torn off by winds.
Antifreeze Can Prevent Damage to Water Pipes
Q: I have a second home in Upstate New York and plan to put in an oil-fired central heating system for my water. I am not there all the time, the water pipes are drained and the traps filled with antifreeze. So, I was wondering if I could protect the water-heating pipes by using the proper mixture of nontoxic antifreeze and water. Can you think of any problems that may occur?
A: There are a few things you should do before adding antifreeze to the house’s plumbing system. First, if the house doesn’t have one already, add a back-flow preventer on the water feed line. This prevents the antifreeze from contaminating the house’s potable water supply.
Next, determine how much antifreeze to add to the system. To do this, estimate the volume of water in the house’s pipes and then add the correct ratio of antifreeze.
A free booklet by the Hydronics Institute has information to help you determine the pipe’s volume and other useful tips. Send a letter with a self-addressed, stamped envelope to: Hydronics Institute, 35 Russo Place, Berkeley Heights, N.J. 07922. Ask for “Technical Topics Number 2A.”
