How to Order a DuraVent Class A Flat Ceiling Kit

DuraVent DuraTech Class A chimney pipe is a great option for venting a wood burning stove when you don't have a masonry chimney. One of the best ways to vent a wood stove is to install the stove and chimney pipe straight up through the ceiling and roof. When the stove is in a room with a flat ceiling, several factors must be considered when choosing the correct DuraTech parts for your chimney system. 

Starting With The Stove

When planning for a DuraTech Class A chimney system installation, stove placement is important to consider. Double check the stove manual to ensure you maintain all necessary clearances from combustible materials. Once the stove is in place measure from the top of the stove for top-exhaust wood stoves, or from the center of the exhaust hole for rear-exhaust wood stoves, to the bottom of the flat ceiling. This will tell you the length of the single wall or double wall stove pipe you need to connect the stove to the ceiling support box. 

Keep in mind, the stove might be positioned where the exhaust hole is not perfectly centered between the ceiling joists. When this happens, measure the horizontal distance from the center point between the ceiling joist and the center point of the stove's exhaust hole. Use offset elbows to offset the pipe over to where the pipe will be able to pass through the ceiling joist.

DuraVent DuraTech Ceiling Support Box

Before the stove pipe will reach the ceiling, the DuraTech Class A Square Ceiling Support Box will be mounted between the ceiling joists and extend down below the ceiling. The Ceiling Support Box allows the stove pipe to connect to the DuraTech pipe while providing the proper clearance to combustibles. 

The Ceiling Support Box supports the weight of the heavy Class A chimney pipe and must extend below the flat ceiling a minimum of 3" (per the DuraVent instruction manual). The Ceiling Support Box is sized so that any size of DuraTech Class A chimney pipe will fit between 16" on-center ceiling joists. A trim collar is included to conceal the cut you make in the ceiling. 

With the Ceiling Support Box in place, you will need the DuraTech Single Wall Snap-Lock Adapter With Trim to connect the single or double wall stove pipe to the ceiling box. If the ceiling box is too long, you can cut it down to size. 

Passing Through The Attic

With the DuraTech Ceiling Support Box mounted between the ceiling joists, we will take a look at installing the DuraTech chimney pipe and insulation shield options. 

In most flat ceiling installations, the chimney pipe passes through an attic space above the flat ceiling. If the chimney pipe passes through an attic space, you must either fully enclose the pipe in a chimney chase or install an Attic Insulation Shield above the ceiling box. Enclosing the DuraTech pipe or installing an Attic Insulation Shield prevents debris from falling into the ceiling box and coming in contact with the chimney pipe. 

If your attic space is greater than 15" from the attic floor to the underside of the roof joist, you can easily install the DuraTech Attic Insulation Shield.

Considerations for Two Story Homes

If your DuraTech Class A chimney pipe needs to pass through a second level of the home before entering the attic, you need to ensure the pipe is fully enclosed in a chimney chase to prevent anything from coming in contact with the Class A chimney. Maintain a 2" clearance between the pipe and any combustible material in the chimney chase. 

Once the DuraTech pipe reaches the second ceiling, you will need to install a DuraTech Firestop Joist Shield on the underside of the second ceiling. In the event of a fire, the Firestop helps prevent the fire from spreading as quickly. 

With long chimney pipe runs, install a DuraTech Wall Strap every 8' above the ceiling box to stabilize the chimney pipe. Once you pass through the second ceiling, you can follow the attic requirements that were just covered in the previous section. 

Passing Through The Roof

Now you are ready to pass DuraTech Class A chimney pipe through the roof. You will need the Roof Flashing and Storm Collar to waterproof the roof penetration. 

DuraVent offers a roof flashing for nearly any roof. You will need to know the roof material and the roof pitch to choose the correct Roof Flashing. For normal asphalt shingle roofs, The DuraTech Roof Flashing is the perfect choice. You will also need a DuraTech Storm Collar to seal around the DuraTech chimney pipe where it passes through the flashing. For metal roofs, we offer the DuraTech Rubber Boot Flashing. 

How Much DuraVent DuraTech Class A Chimney Pipe Do I Need?

As previously mentioned, the Ceiling Support Box must extend at least 3" below the ceiling. You will need to measure from 3" below the first ceiling to the bottom of the roof deck to determine how much pipe will be inside the home. 

The chimney pipe height above the roof for code compliance depends on the roof pitch and the lateral distance from the roof penetration to the roof peak. This is often referred to as the 3-2-10 rule (3-2-10 rule explained). 

Combining the total length of the pipe inside the home and the height required by the 3-2-10 rule will determine the total chimney pipe needed. Keep in mind that if you need more than 5' of pipe above the roof, you will need the DuraTech Extended Roof Bracket to stabilize the pipe above the roof. 

The final part of any DuraTech Class A chimney pipe installation is the DuraTech Class A Rain Cap to prevent rain from entering the chimney. An optional DuraTech Spark Arrestor is available if local building codes require a spark arrestor, such as in California. 

Additional Considerations

In some situations, the Ceiling Support Box and the roof penetration do not align and you may need to offset the DuraTech Class A Chimney. You can achieve an offset by using two offset elbows. The Elbow Kits are available in either 15-degree or 30-degree angles. Put a section or two of the DuraTech Class A chimney pipe between the two elbows in order to achieve the necessary offset. Here is a helpful measurement guide that will walk you though taking the proper measurements for a flat ceiling chimney installation.