Bracing should quiet creaking sounds coming from attic

Q: The attic in our 4-year-old house creaks, and when it’s windy we hear cracking noises as well. The sounds are loud, waking us up. The builder sent a fellow to add 2-by-4s to some of the trusses. It didn’t resolve the problem. What is causing the creaking, and how can we stop it?

A: Although I’m not a structural engineer, I have built enough wood-frame houses to know that they can groan, creak and moan when the wind is howling.

In severe windstorms, it’s normal for a house to make a few noises.

Imagine the surface area of your entire 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 is experiencing the wind.

The mathematical formulas for calculating such forces are complex. Modern building codes have taken all this into account, however, and the trusses in your home should have been designed to withstand normal weather events and windy days.

As for what’s causing the problem and the noise, it’s pretty simple: 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 you could be getting noise from wood rubbing against metal fasteners.

The solution, in my opinion, 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 in sending a worker to add more bracing to the underside of the trusses, but the bracing might not have been installed correctly.

I would hire a residential structural engineer to inspect your attic. Fortunately, it’s wide open, so he or she can see all the framing members. Be sure the engineer is a residential expert with substantial experience in working on houses that creak in the wind. Ask for references.

My guess, based on engineered drawings from which I have worked, is that the engineer will come to your home and take notes and photos, do a detailed inspection of your attic space, then develop a simple retrofit plan that most carpenters can follow.

The plan will show added bracing that will be placed within the trusses.

Following the plan to the letter and using the correct fasteners is crucial.

The wild card is the construction of your exterior walls on the first floor of your home. 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 oriented strand board or plywood sheets nailed to the wall studs so the walls can’t shake under wind or seismic loads.

Any photos you might have of the house as it was being built, showing the wood-framed walls, would be helpful to the engineer. I have advocated for years that homeowners take hundreds of photos of their homes as they are built.

The most important photos are those that show areas that will eventually be covered by insulation, drywall, vinyl siding, shingles or any other material.

Tim Carter is a columnist for Tribune Content Agency. He can be reached via his website, www.askthebuilder.com.