The attic in our four-year-old house creaks, and when it’s windy, we hear cracking noises as well. It sounds as if something is going to come crashing through the ceiling above our bed. The builder sent a fellow to add 2-by-4s to some of the trusses. It did not resolve the problem. What’s the problem, and how can we stop the frightening creaking?
— Martha A., Egg Harbor Township, N.J.
While I’m not a structural engineer, I’ve built enough wood-frame houses to know that they can groan, creak and moan when the wind is howling. Even my own home, which I didn’t build, creaks and strains when powerful nor’easters batter her.
If your home creaks and moves with each slight breeze or moderate wind, I would say you have a valid complaint. But in severe windstorms, it’s normal for a house to make noises.
It’s easy to understand what’s going on if you’ve ever had to carry a single sheet of plywood or oriented strand board (OSB) in a strong wind. I clearly remember a gusty day years ago when, as a young carpenter, I hoisted up a piece of plywood and promptly was put on the ground by Mother Nature.
I didn’t get hurt, but the pressure of the wind on that single sheet of plywood was far greater than the combined strength of my leg, arm and back muscles to resist the force.
Imagine the surface area of your roof or the side walls of your house. Structural engineers will tell you that the combined pressure of a moderate wind is equivalent to thousands of pounds of force, depending on the surface area of the structure that’s experiencing the wind.
The mathematical formulas for calculating this are complex. Modern building codes have taken this into account, and the trusses should have been designed to withstand normal weather events and windy days.
When the wind is blowing against your roof or your attic side walls, the pressure of the wind is causing the wood framing to flex. The wood sheathing could be rubbing against the trusses, and the noise could be from wood rubbing against metal fasteners.
The solution is to stiffen the attic structure so that much more force is required to make it flex or move. Your builder had the right idea to add more bracing to the underside of the trusses; however, it may not have been installed correctly.
I’d hire a residential structural engineer to inspect your attic. Be sure he or she is an expert with experience in working on houses that creak in the wind — and can prove it. Ask for references and call the homeowners to see whether their houses stopped making noises after recommendations were followed.
The engineer should take notes and photos, do a detailed inspection of your attic and develop a simple retrofit plan that most carpenters can follow.
The odds are that the plan will show all sorts of added bracing that will be placed within the trusses. The engineer’s plan will specify the type of nails or screws, how long they must be and how many should be installed at a given location.
The construction of your exterior walls on the first floor of your home is the wild card. It’s important that the walls of the house were built with sufficient diagonal bracing so they don’t move, either. This bracing can be metal strips cut and nailed into the wall studs, or it can be OSB or plywood sheets nailed to the wall studs so the walls can’t rack under wind or seismic loads.
If you have photos of the house while under construction showing the wood-framed walls as they were being built, those will be helpful to the engineer.The most important photos will show things that eventually will be covered by insulation, drywall, vinyl siding, shingles or any other material.
It’s important to be able to see what’s behind or inside a wall. I suspect once you find a carpenter to complete the installation of the bracing in your attic, all will be well and you’ll sleep peacefully on all but the worst windy nights.
Tim Carter is a columnist for Tribune Media Services. Contact him through his Web site: www.askthebuilder.com.