A chimney chase is the framing that hides the flue pipe — the rectangular rooftop structure that emits smoke from a lit fireplace — and typically uses steel or wood materials. Often, the exterior chase gets covered in brick or stone veneer, wood or stucco.
Chimney chases are similar to other household framings and comprise planting studs and sheeting to create a box. Inside your home, the chase will have an opening large enough for a functioning firebox or fireplace insert. Likewise, on the roof, it’ll leave an opening on top for the smoke to come out.
Handy homeowners can build a chimney chase themselves. While it’s not a particularly complicated project, they will require the necessary skills to do so efficiently.
6 Steps to Build a Chimney Chase
Your flue may require a new chimney chase for various reasons, such as to hide an unsightly duct or rehab an older chimney. The following six steps can guide skilled homeowners to build a chimney chase onto their homes.
1. Determine the Dimensions
Before you buy the materials for this project, you must know the dimensions of the chimney you’re looking to frame. You can count on measurements to be about 3 feet by 5 feet to clear the roof, while six feet is standard for a fireplace insertion and mantle.
It’s critical to follow the manufacturer’s requirements and ensure you meet local building codes. For instance, your chase dimensions will have to accommodate gas line access and be capable of supporting structural weight.
2. Mark the Dimensions
When you’ve figured out the chase measurements, you’ll want to mark them accurately and clearly in your workspace. Using a ruler and chalk pencil, measure the correct distance off the wall on the ceiling. Then use a plumb bob to provide a vertical reference on the floor for each point.
You’ll also need to mark the outside chase — whether it’s the part of the protruding chimney on the roof or runs up alongside the house.
3. Choose Your Materials
Selecting suitable materials for your chimney chase is essential. Wood framing may be susceptible to wall and roof flashing, causing structural damage and rot. As a result, your chimney chase may become unstable, giving room to leaks, pests and rodents.
Stainless steel and copper are ideal chimney chase materials for long-term use, proving durable, rot-free and rust-free under harsh weather conditions. Of course, the downside is homeowners will have to pay a premium for these casings.
However, you might look at the initial costs as an investment for cutting expenses in the future. Less durable materials will likely need replacement after a few years.
4. Cut the Pieces
When you’re ready to build a chimney chase for your home, you’ll need to cut the materials to the correct sizes. Approximately 16–24 inches is enough space between each stud frame for the interior chase. Stacking two 2-by-4 blocks and cutting the studs to reach the chalk mark on the ceiling will account for the bottom and top plates.
Additionally, you’ll need to cut full-length studs for the side of the chase, cripple studs for between the plates and a header that runs across the front section of the firebox. You can follow a similar method when cutting the materials for the exterior portion of the chase. A prefabricated chimney chase — in which components are assembled elsewhere and attached to your home entirely constructed – is an option to scale back the work.
5. Nail the Pieces in Place
Assembling the chimney chase should be straightforward. After laying the pieces out where they belong, nail each full-length stud to connect the top and bottom plates. Cripple studs and the header should get installed next.
Nail the side studs according to where you marked their appropriate location. It may be necessary to ask for assistance to hold the chase steadily as you nail every level into the top and bottom plates.
6. Fireblock Your Chimney Chase
You must consider fire resistance when you build a chimney chase. Therefore, it’s best to hire a fireplace installer to create a fire block that meets your local municipal codes.
The Chimney Safety Institute of America says chimney fires can ignite at 451° Fahrenheit — fireplaces can reach 450° F — and burn at nearly 2,000° F. A fire can cause flue tiles to crack and metal to melt in minutes at that temperature.
Fireblocking aims to slow and prevent fire, reducing its intensity throughout the chimney chasing between the floors and walls. After installing the appropriate fireblocking, you can cover the frame with plywood or steel and add a stone, brick or stucco facing and metal chase cap.
A Well-Constructed Chimney Chase Ensures Fire Safety
Material selections and sound chimney chase construction will ensure fire safety for future use. Homeowners with the skills and know-how to build a chimney chase can create a box that protects their home long-term.
