Skip to Content

Running Ductwork Through Floor Trusses: All You Need to Know

A good ductwork system can save your management costs while protecting you from a lot of trouble.

However, running ductwork is a complicated process. Thus, finding the right place for your ducts to move is important.

You might ask, is running ductwork through floor trusses possible? 

The answer is yes! You can run your trusses through the ductworks of your house. However, you have to make sure your trusses are sturdy enough to hold them. Also, you need to use specific materials and choose the right size for safety.

In this article, we’re going to discuss everything you need to know about floor trusses! And discuss whether your floor trusses are strong enough to house your ductwork. Let’s begin! 

How Do Floor Trusses Work And Why You Need It? 

We need to know how trusses work before we discuss the technicalities. Trusses are wooden structures made to support the roof. They’re incredibly strong wooden structures that hold the strength of your wood. 

Generally, trusses are made of 2×4 lumber and are placed based on your needs. They’re made in multiple shapes and sizes. So, you can customize them to fit your needs. 

You can place your trusses in two ways. You can use your trusses to span a large distance or a short distance on your roof. If they’re spread long enough, they will transmit the weight to the exterior walls. Thus, preventing any load on the internal ones. 

Trusses are important for the balance of your house. They act as a bridge between the walls and the roof. As a result, the weight is spread evenly around. Also, this gives you an additional space to house your ductwork easily. 

Also, if they’re long enough, you can move or relocate them based on your needs.

Running Ductwork Through Floor Trusses: Necessary Steps 

To put your ducts through the trusses of your house, you need to keep some things in check. 

If you plan to run your ductwork through the trusses, you have to decide early. Planning and deciding early makes the process a lot more convenient! 

Before we proceed to the steps, we need to gather some tools for the operation-

Required Tools:

  • Ductwork 
  • Sheathe 
  • Utility Knife
  • Mastic
  • Tape

Once you’ve gathered the tools you are ready to do the ductworks. The steps required to help you run your ductwork through floor trusses are-

Step 1: Design Accordingly

The planning of your trusses should be confirmed and approved before building. The duct layout should be done beforehand. Important factors such as the designs for the floor joists, ceiling soffits, and other cavities must be mentioned.

The design must be in accordance with the ACCA Manual D (ACCA 2009). Also, Relevant factors must be kept in check. These include the insulation of duct chases, air-sealed metal, flex or fiberboard ducts. 

Once the design is complete, prepare the materials.

Step 2: Choose The Correct Building Materials for Truss 

You have to make sure your trusses are strong enough to hold your ductwork. For this reason, you need the correct material. If your trusses aren’t strong enough, they won’t be able to hold the weight of your ductwork. 

Use materials such as galvanized steel, aluminium, fiberglass duct board etc. to make your ducts. They’re proven to be very sturdy. Ideal for your roof as well as anything that goes inside. 

If you have an Aluminium roof, get the patio of your roof insulated. This will prevent the ductwork from overheating. 

These are some things we need to keep in check during construction! 

Step 3: Put The Ductwork in Place 

Putting the ductwork in place is a bit technical. You need to make sure you’re following the ductwork and know the position of the vents. Mark the supply and return ducts carefully. Otherwise, repairing any faulty duct would be a hassle. 

If you have ductwork running between floors, make sure you have a map of your ducts. It’s very useful in the long run, especially when your ducts need replacement.

Step 4: Close the Ducts 

Now that the ductwork is in place, you need to close the ducts carefully. We recommend that you put the ductwork before you sheath the wall. It helps the sheathing set in better without causing trouble. 

It’s better to leave a part of the sheath loose or open. This will help you during repairs. You can also choose to not sheath the joist band for easy access. Use some duct tape to close the open part. 

Close all the supply and return connections with mastic tape. However, make sure the markings aren’t covered. If you have to cut holes for your joists, fill them up as well. Use tape to cover any remaining holes or gaps. 

Make sure the tape you’re using is of industrial standard. If you’re wondering which tape to use to close your ducts, we got you covered! Check out our recommendations for the best mastic tapes: 

Product 1
Product 2

These are some of the best products available out there! You can check their reviews for more information! 

Step 5: Test The Ductwork 

Now that everything is done and ready to go, you need to place the drywall. However, we recommend that you do a final evaluation of everything.

You won’t have access to most cavity spaces in the ducts. So, we suggest doing a duct-blaster test of the entire system. This will help you detect any issues within the system and you can fix them immediately. 

With that, we’ve discussed everything about running your ducting through the floor trusses. We hope you find this article helpful!


Question: Can you cut the floor joist for HVAC?

Answer: While you can cut your floor joist for HVAC, it’s not recommended. Any accident can cause serious damage to the structural integrity of your house. 

Question: How to cover my ductwork?

Answer: The easiest way to cover your ductwork is by using drywall over it. You can also choose to paint or use household appliances to cover it. 

Question: Should return air ducts be sealed?

Answer: Yes! Return air ducts need to be sealed properly. Otherwise they won’t remain airtight and might leak out! 

Final Words

Taking care of your ductwork is a mammoth task. Any leaks or mistakes can increase your electricity consumption greatly. Thus, resulting in a lot of wastage and high electricity bills. So, dealing with them is important. 

Running ductwork through floor trusses is a great way to keep your ductwork safe. We’ve discussed the steps in this article to help you out. 

We hope you find it helpful!