Designing Your Wall Exit Flue System: Step by Step
Our newly updated Kit Builder is great at figuring out just what you need for your installation including wall exits and offset pipe. But if your installation needs a little additional planning or you just like seeing how the sausage is made, this guide will walk you through the process of designing your custom wall exit chimney system. After working through the following steps, you should know exactly what you need to purchase or at least have a pretty good idea that you can run by our team of tiny stove experts along with any questions you have.
Step 1: Calculate Horizontal Pipe Needs
Calculating the length of horizontal pipe you'll need might seem straightforward but it is the most challenging calculation in planning your wall exit. It must take into account: which part of your stove/pipe will be closest to the wall, safe clearances, pipe geometry, and wall thickness. We will walk you through the process and provide charts to help you determine what you need.
Stove Orientation and Stove Flue Exit
Decide which side of your stove will face the wall and which flue exit you want to use on the stove (top or rear). Find the chart below that matches your installation plan and use it to make your calculations and get your horizontal pipe needs.
Take Measurements
You’ll need to know three numbers:
- Wall Thickness - Measure from the finished interior wall to the finished exterior wall
- Distance to Wall - The distance from the closest part of the stove or pipe to the wall - review the minimum distances required and use the larger of the two clearance requirements for your setup.
- Minimum Safe Clearances:
- Use the clearance requirements to determine how close your stove and pipe can be to the wall given the type of heat shielding you will be using.
- Minimum Clearance for Pipe Geometry: 6.75” minimum
- Minimum Safe Clearances:
- Pipe Distance from Exterior Wall - This calculator assumes your exterior flue pipe will be 2.75" from the exterior wall. If you need additional distance to get around eaves you can either add additional length to your horizontal pipe or use elbows to offset your chimney. Ideally, you should use elbows over a longer horizontal section wherever possible. See Step 3 below for details on offsets.
Add your wall thickness to your distance to wall (plus any additional length needed for your pipe distance from exterior wall) to get YOUR NUMBER.
Check the Chart
On the chart matching your stove size, find the range in which YOUR NUMBER falls to determine which length(s) of pipe you’ll need for your horizontal run. You’ll also be able to see the minimum vertical height for your flue based on the horizontal run length. We advise using a vertical flue pipe of at least 80 inches for any Dwarf stove wall exit installation. Additionally, ensure a minimum vertical flue pipe height that is three times the length of the horizontal run.
Write down the length(s) of double wall insulated pipe you'll need for your installation.
Step 2: Calculate Your Single Wall Pipe Needs
Total single wall pipe needed = Vertical distance above the stovetop to the center of the wall exit.
- Check the clearance requirements to ensure you are planning enough space and the right type of shielding around your single wall pipe for your walls and ceiling.
- The wall exit installation kits include an 11”-16” adjustable telescoping single wall pipe. Subtract 14" from the total length of the single wall pipe needed to find the additional length of fixed single wall pipe needed. The telescoping pipe will then give you some room for error in either direction.
- If using the rear exit tee on your stove, the distance from the top of the tee will be within an inch or so of the distance from the top of the stove to the center of the wall exit so you can use the stovetop for calculations.
- If your flue design requires elbows for an offset to get around rafters or other obstructions, refer to the Offset Charts linked below to determine how much vertical space will be taken up by your offset. Take this into account as well when planning your vertical pipe needs.
- Higher is better. Keeping as much of the flue as possible inside of the living space keeps your flue gases hotter, resulting in easier startup, cleaner burning, and less maintenance.
- More single-wall pipe inside also means you keep more heat in your living space instead of losing it up the flue.
- Finally, single-wall pipe costs less than insulated pipe, so the more you single-wall pipe you use, the less your overall installation costs will be.
Step 3: Calculate Vertical Double-Wall Insulated Pipe Needs
- Measure the vertical distance from the center of the wall exit to 3’ above the edge of the roof or 2’ above the highest part of the structure within 10’ of the flue pipe. This rule, called the 3-2-10 rule, affects the safety and performance of your stove installation.
- Subtract 6” from this number to account for the vertical portion of the insulated tee. This will give you the amount of Vertical Double Wall Pipe needed.
- If your flue design requires elbows for an offset to get around eaves or other obstructions, refer to the Offset Charts linked below to determine how much vertical space will be taken up by your offset. Take this into account as well when planning your vertical pipe needs.
Step 4: Other Parts Needed
All of the below items are necessary for most wall exit installations and are included in our Wall Exit Installation Kits
You can also find each part individually in our shop under the pipe diameter size required for your installation.
- 90 Degree Single Wall Elbow - connects the vertical pipe coming out of the stove with the horizontal run through the wall
- Wall Thimble - provides a safe penetration adhering to the required 2” clearances for double-wall pipe.
- Single-to-Double Adapter - allows you to transition from our single wall pipe to the double wall insulated pipe required for a wall penetration
- Insulated Tee - makes the exterior 90º turn to connect the horizontal through-wall pipe to the vertical section of exterior pipe.
- Tee Support Bracket - secures the insulated tee to the wall and supports the overall weight of the exterior flue pipe
- Wall Support Bracket - Use at least one mounted as high on the wall as possible to stabilize the exterior flue pipe. Use one bracket for every 6’ of pipe.
- Roof Vent - Both the Shielded and Compact roof vent keep rain out of your flue and include a spark arrestor. The Shielded Vent has additional side shielding to block sideways rain and improve performance in very windy conditions.
- Clamps - Every pipe joint must be secured for stability. We recommend clamps for every joint, but you do have the option to secure the single-wall joints with stove pipe screws since they are inside the structure and not subject to outside elements. We do not recommend using screws on the exterior double-wall pipe because it provides a point for rain/water to infiltrate the pipe wall.
- Stove Gasket Cement - for sealing the first section of single wall pipe into the stove’s flue flange
- High Heat Silicone - for sealing the thimble flange to the exterior siding of your structure
Optional Parts
- Extended Roof Support - If your flue extends more than 5′ above your roof line, you need an extended roof support bracket to provide lateral support to the vertical pipe. The bracket clamps to our double wall insulated pipe and uses two adjustable arms to secure the flue to the included L-brackets attached to your roof. In windy areas or climates that receive high snow loads, an extended support bracket may be necessary for shorter flue as well. In addition to the support bracket, you may also want to use a snow splitter to divert snow and ice from pushing the pipe over as they slide down the roof.
- Pipe Heat Shields - These are a simple and attractive option to safely reduce your clearance requirements from combustibles down to 6” for the single wall pipe. Alternatively, you can put up shielding on your walls. See the clearance requirements article about different types of heat shields and their clearance reduction capabilities.
Questions?
Congratulations! If you’ve made it this far, you should now have a complete list of flue parts for installing your stove. Please be sure to also add to your cart any stove or pipe heat shields you need to maintain the safe clearances you’ve planned, stove upgrades like the Direct Air Intake or Wood Storage Stand, and any other Wood Burning Accessories to make your life easier/more fun.
We recognize that planning a wall exit can be challenging. Our team of experienced wood stove guides is available to assist with any questions that might come up with the above process. Please reach out to us support@tinywoodstove.com or use the contact form below.