Whether you're redoing your attic or building a home, a home attic project can be a daunting task. It's important to know what you're doing and what not to do before you start so you don't make a big, irreversible mistake. Attic trusses are one of those things that you don't want to mess up. But don't worry: we've done the research on attic trusses for you.
You should not drill, cut, or notch your attic trusses. These actions will significantly weaken your trusses. If you have to modify your trusses after the final design has already been approved, consult an engineer.
Can you screw into attic trusses? Do roof trusses need support in the middle? How do you strengthen roof trusses? Keep reading to learn the answers to these questions and more.
Why Is Drilling Into Your Trusses Bad?
Trusses are structural support in the attic to support the roof. They are usually cut to support a specific weight load where the stress is distributed depending on the material, length, and width. Trusses also allow for a certain amount of deflection for hard winds or small earthquakes. Drilling holes into your trusses, even small ones, compromises their structural integrity and weakens the amount of support they can provide.
Furthermore, drilling or modifying attic trusses violates most building codes. Codes vary depending on your location, but general codes prohibit any alteration to trusses after the initial design is approved (except for extenuating circumstances). Even then, it's best to hand the job over to an engineer. Take a look at R802.10.4 in the International Residential Building Codes for more information on the rules against modifying trusses.
Can You Ever Cut Into Attic Trusses?
You cannot cut into attic trusses. Like drilling into trusses, cutting or notching your trusses compromises the structural integrity of the trusses and violates building codes. Your trusses should be cut to fit before installation. If you have concerns that you can't fix without cutting into your trusses, contact a professional in your area.
Can You Screw Into Attic Trusses?
It is possible to screw into your truss, but it's risky. You would still be modifying the stress distribution on the truss, but significantly less so than cutting or drilling. However, only screw into your truss if it's absolutely necessary, and consult the engineer who designed your attic before you do. You can remove a screw, but its mark will be there forever.
Do Roof Trusses Need Support In The Middle?
Depending on the design of the roof trusses, there is already a central support beam to aid with bearing the weight of the roof above it. Only a few truss designs don't contain a central support beam.
Most domestic roofs don't require additional support for roof trusses. This is because most homes are typically small enough for the trusses to support their own weight as well as the roof above them.
However, in large homes and in industrial settings, trusses may need support in the middle. These roofs are generally much larger and often have heavier, more durable materials for the roof that make it more difficult for the trusses to support. Generally, trusses can span 30 to 50 feet without any need for additional support. So, for your home attic project, your trusses likely don't need support in the middle.
How Do You Strengthen Roof Trusses?
Trusses are made of triangular frames to better support the roof. The longer beams of wood allow for more stress distribution and more weight. To strengthen your trusses, you can add vertical beams as additional braces, also known as cripples. Here are some basic steps on how to add cripples to your attic trusses:
Supplies you'll need:
- Measuring tape
- 2x4 wood plank
- Circular saw
- 1/2-inch plywood board
- Utility knife
- Construction adhesive
- Staple gun
Start in the center of your trusses and measure the distance to either wall, using a pencil to mark the distance in thirds. You can always add more cripples, but two braces on either side is a typical addition. Measure each truss separately so your marks will all be even and the same distance from the wall.
2. Mark The 2x4
Hold your 2x4 up to your truss so it intersects at a 90-degree angle. Mark where the 2x4 meets the top and bottom truss. The top will have a slanted portion.
3. Cut The 2x4
Using a circular saw, cut the 2x4 where you made the marks, making sure your cuts are straight and precise. Duplicate this piece for the other side of the truss and for the other trusses in your attic. Then, carefully wedge the cripples into the space between trusses so that the 2x4 is resting on top of the bottom part of the truss and sits under the top slant.
4. Add Supports
You don't want your cripples just sitting in your trusses without being fixed or attached, so using some cardboard, trace the joints at the top and bottom of where your cripple connects with the truss. Your cardboard tracing will be a template for plywood gussets, which are less aggressive than metal ones and don't require you to add holes to your trusses.
5. Cut Out The Plywood
Using the cardboard templates as a guide, cut out gussets made of 1/2-inch plywood and carefully apply them to your cripple joints using construction adhesive. Hold them in place until the adhesive begins to set. For additional support and security, carefully staple the gussets into place with a staple gun.
How Do You Repair Attic Trusses?
After many years, attic trusses may become weak and need repairs and reinforcements to keep the roof stable and supported. You can use plywood to create bracers for trusses with minor issues, or you can use metal bracers for trusses that need a bit more help. Here are some quick steps on how to make your own plywood bracers:
Materials you'll need:
- Plywood sheet
- Wood glue
- C clamps
- Wood screws
You'll want to start by determining the areas of your trusses that need additional support and measure the width of the areas. You then mark these spots on your plywood sheet.
2. Cut Out The Plywood
Using a circular saw or another cutting tool, carefully cut out sections of the plywood sheet. You'll want two identical sections of plywood sheeting for every section of the truss you want to repair. This way, you can apply a bracer to both sides of the truss for support.
3. Glue On The Bracers
Aligning the plywood sheets as best you can, use wood glue to align bracers on either side of your truss and hold them into place with a C clamp until the glue dries.
4. Add The Wood Screws
Once your glue has dried, you will want to secure your plywood bracers even further with some wood screws. These will limit the additional stress on your trusses as much as possible. Try to avoid using the screws in damaged areas of the trusses. Instead, make sure your plywood bracers extend past the damaged area enough for you to insert screws into the solid truss.
Attic trusses are vital to keeping your roof stable and supported, and you should never cut or drill into your trusses, as this might weaken or damage them. There are several ways you can add additional support to your attic trusses, such as inserting cripple braces or repairing weakened spots. We hope you've learned something about trusses and feel confident working with yours.
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