What to do about rusty posts

Q. I have several posts in my basement holding up a center beam. They are steel filled with concrete, and are developing one-quarter-inch holes with rust showing through. My husband sanded off the rust and painted the posts, but the rust persisted. What can I do now? Will the posts continue to hold their weight?

WORRIED

A. I don't think there is a lot to worry about. Moisture is coming up through the concrete floor, and moves into the concrete in the post and then rusts the steel. The British have a quaint name for this: rising damp. The post itself is rusting on the outside from water vapor.

The house is unlikely to collapse, but there are things you can do to tackle the rust and prevent more moisture from getting into the air and into the post. Ideally, you can replace the posts and put a vapor barrier under each post as it is installed. This will prevent water vapor from getting into the post.

The next best thing will work: Build a wood box around the post, sealing it at the bottom and top. This should keep moisture in the air off the post, but it will not do anything for the moisture in the post itself.

Also, ventilating the basement in the summer, or using a dehumidifer in the humid months of July and August will reduce the water vapor, but is unlikely to fix the problem of moisture in the post.

Here's another possible solution: Shore up the beam on both sides of the post, cut it near the bottom so you can put down a piece of plastic (vapor barrier), then put a pressure-treated timber or concrete block under the post, and release the shoring posts.

It may be a jury rig, but it can work. Since this latter work involves the structure of the house, the work should be done by a professional, or at least have a professional advise you.

Q. My aluminum siding (circa 1965) needs painting. I have two offers, one using a brush and roller, another a high-powered sprayer. Which is better?

CURIOUS

A. One of the most important parts of an exterior paint job is to put as much pressure in the application as possible for the paint to get into the existing finish instead of lying on the surface. I think this is best done by high-pressure spraying, so go with the sprayer.

Q. I have a flat rubber roof. My roofer said I should paint it white or silver to reflect heat. Is that a good idea?

VIRGINIA BEACH, Va.

A. You bet. Light-colored roofs reflect heat in Southern climes. It is not necessary in the North, but essential in the heat of the South. To give you an example of how true this is, recall going to the beach on a scorching hot day. Walking on a black asphalt parking lot in your bare feet is almost impossible; you have to curl your feet to keep from getting burned (almost). You couldn't wait to get to light-colored sand, which might even be cool in the sun. Later you had the smarts to wear sandals.

Q. I have a screw stuck in a wood stud, and no amount of coaxing, twisting, or any other removal method is working. A hardware man suggested grabbing it with needle-nosed pliers and twisting, but I can't even grab it. The screw is attached to a broken plastic bracket. What now?

ANNE CULLEN, Cambridge

A. OK, some ideas:

1. First and always, spray it with WD-40.

2. Saw off that plastic bracket; it might reveal enough of the screw shaft that can be turned by a pair of regular pliers.

3. If the screw head has a slot, place a screwdriver on the right side of the slot and tap lightly with a hammer, turning the screw counter-clockwise. This will also work with a Phillips-head screw. An auto mechanic taught me that trick.

4. Buy a screw extractor (not expensive at hardware stores), and drive it into the screw; the extractor will automatically reverse the twist and - voila! - out it comes.

5. Cut off the bracket and dig the screw out. Not pretty, but you can fill the hole with wood filler.

Q. Do you know anythng about ductless air-conditioners?

TONY, from Andover

A. I have heard a bit about them. They are the ones usually installed over windows, and they act as window air conditioners but without the problems that come with window units.

They are ductless because, well, there are no ducts to string around the house. Instead, I believe they cool from the gas-filled copper tubing that carries the refrigerant from the compressor. Those tubes are easier to string through walls and other hard-to-reach areas. They are most popular when you do not have ducts already in the house in a hot air heating sytem.

Q. I had a bat in my house, and the bat was removed. Now I have to seal a door in the knee wall leading to eave space where I think the bat came in. How can I seal that door? I don't use it very often.

SUSAN, from Boston

A. If you don't mind how it looks, cut a piece of polyethylene plastic several inches bigger (on all four sides) than the door. Fold each side of the plastic so you can staple the plastic around the door. Staple the bottom fold on the floor.

A more permanent and attractive fix is to tack a piece of plywood on the door at the top and side. Weatherstrip the bottom and staple a flexible rubber-like flange on the hinge side.

Globe Handyman on Call Peter Hotton also appears in the Sunday Homes Section. He's available 1-6 p.m. Tuesdays to answer questions on house repair. Call 617-929-2930. Hotton also chats on line about house matters 2-3 p.m. Thursdays: Go to Boston.com. Hotton's e-mail is photton@Globe.com