Mar 26, 2015 4 min read

Globe Handyman on Call Peter Hotton is available 1-6 p.m. Tuesdays to answer questions on house repair. Call 617-929-2930. He can be reached at phottonglobe.com.

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Q. After one of the blizzards, I went upstairs to find snow on the floor of my single-family home’s attic. The snow is entirely on the north side of the house, and at some points was a substantial pile. Any thoughts on what could be causing this? The roof was redone a few years ago, but the folks who did it (whom I did not hire) may not have done it correctly. They also did the siding and put up the gutters. I had some contractors in to do work over the summer and they noted some problems with the old contractors’ work — for example, in places they used finish nails to put up the shingles. I did have these new contractors check to see and repair any holes in the fascia on the north side. Should I call a roofer, general contractor? I do not know where to start.

ODETTE WILLIAMSON

A. This question was asked several weeks ago, but I don’t think I gave it enough thought the first time. So, once more into the figurative breach!

You did not say if the roof has a ridge vent or vents anywhere else, but the snow could have blown through the north side of a ridge vent by strong winds. Or it could have been condensation by moist air on the cooler (north) side of the vent. This is harmless, but it can be corrected by more insulation on the attic floor and more vents: in the soffit, which is the under part of the roof overhang. The best soffit vent is a continuous 2-inch wide screened strip along each soffit.

There don’t seem to be other problems, and if they nailed shingles with finish nails they probably face-nailed them high under the roof overhang where they won’t show. Let’s hope they were galvanized finish nails. This is a minor problem, unless they start to rust. As for who to call, I think there seem to be several vague problems for a general contractor to handle.

Q. My wife and I are getting ready to sell our house. We have a white substance on part of our basement walls. I have been told that it is efflorescence. The parts of the walls where it appears are below ground, but it’s only on a portion of the walls. Do I need to get this off the walls before selling the house? Is it harmful? It is hard to clean off. Am I better to hire someone to do it? LOU WEISZ

A. Yes, it is efflorescence, which is lime being leached out of the concrete by water. It is harmless but annoying, and scary for the uninitiated. The walls are wet from condensation of warm humid air escaping into the basement. It can be corrected by venting the basement, and insulating the basement ceiling. Insulate that ceiling with 9-inch fiberglass batts with the paper vapor barrier up, touching the ceiling boards between joists. Or insulate that space neatly by inserting 4 or more inches of rigid foam insulation such as Styrofoam insulation. Sweep it off with a broom and then dispose of it. It will come back if you don’t do something about it.

Help for heating problem

I thought I might toss in my two cents worth regarding the homeowners’ problems concerning high carbon monoxide readings within the boiler cabinet. It sounds to me that the gasketing and/or refractory cement used to seal between the boiler sections. Before junking a good system, I would advise a thorough boiler cleaning and burner set up, along with checking the boiler for leakage of combustion gasses. FRED HAYES

Q. I have brown water stains on one of my ceilings. A man at Home Depot suggested spraying the stains with white Kilz spray, then a coat of white latex ceiling paint.MICHAEL

A. Yes, that will work, but don’t forget the mold in the middle of that stain. Treat the mold with 1 part bleach and 3 parts water, and continue over the entire ceiling with this solution, which can also take off other stains. I would be careful using the Kilz because it is so intensely white that it is hard to cover with one coat of ceiling paint. So if you use the Kilz, do the entire ceiling (in that room) before using the ceiling paint. And remember, when using bleach or bleach mixes, you must rinse any bleach solution you will be applying thoroughly before adding any more finishes.