Installing a wood stove pipe through an exterior wall, known as through-the-wall or wall pass-through venting, allows homeowners to route the stovepipe directly to the outdoors. This venting method is an alternative to venting through the roof or chimney when the stove location makes it difficult or impossible to use conventional interior venting.
Venting a wood stove through the wall has several advantages. It provides a shorter, more direct venting path in spaces where the chimney or roof vent is not conveniently located near the stove. Wall venting may also be less expensive than extensive interior vent pipe runs. For homes with low-pitched roofs, it can be the only viable venting option. Exterior wall vents are also easier to inspect and clean than chimney vents.
However, venting through a wall has special safety considerations. Maintaining proper clearances from combustible materials is crucial to prevent fire hazards. The installation must also meet local building codes and be properly sealed against the elements. This guide provides a complete walkthrough of the wood stove wall venting process so you can cut through the confusion and vent your stove safely and effectively.
Planning Your Installation
Assessing Your Layout
The first step in planning your wood stove wall vent installation is assessing your available layout options. Determine whether an interior chimney or roof vent is feasible based on the stove’s positioning within the home. Wall venting is best suited for stoves located on exterior walls away from existing chimneys. You will also need to decide between venting directly through the wall behind the stove or offsetting the pipe to pass through a different area of wall. Offset vents allow more flexibility in stove placement but involve additional elbows.
Consider how the venting route will impact the room layout. Avoid passing through high traffic areas or removing windows. A qualified professional can help evaluate the best location based on your floor plan, taking into account stove size, available routes, and termination requirements.
Safe clearances from combustible materials must be maintained for any wood stove installation. The National Fire Protection Association (NFPA) recommends a minimum of 18 inches between stove pipe and combustibles. However, clearances may be reduced by installing heat shields constructed of 24-gauge sheet metal.
For wall pass-throughs, it is critical to maintain at least 1 inch of clearance from pipe to wall framing. Any wood framing or other combustible materials surrounding the vent pipe should be cut back to allow 1-inch air space. Proper clearances are what make wall thimbles necessary.
Choosing Your Venting Route
Once you have determined feasible locations, decide on the best route for running the vent through the wall. A straight, direct path is preferable when possible, as offset vents with elbows are more prone to drafting issues. However, offset vents allow flexibility if the stove is not located directly on an exterior wall. Inspect the exterior to make sure the planned vent termination location will meet code requirements for distance from windows, openings, and property lines.
Venting a wood stove through the wall requires specialized components to provide structural support and protect combustible materials:
- Wall thimble – A metal sleeve installed in the wall framing that the stove pipe passes through. Maintains proper clearance.
- Pipe sections – Either single or double wall stove pipe cut to length.
- Elbows – 90 degree angle connectors to offset pipe runs.
- Supports – Brackets or straps for securing pipe sections in place.
- Termination cap – A cover placed at the pipe’s exterior outlet.
High temperature sealants, insulated pipe, and roof flashing may be needed as well. Having all required materials on hand before starting will make the process go smoothly.
Insulation and Firestopping
Sealing gaps around the vent pipe is crucial for fire safety and preventing drafts. Firestop caulking fills voids between wall framing and the thimble. High-temperature insulation like rock wool can be packed around the pipe where it passes through interior ceilings or attic spaces to prevent heat transfer.
Metal firestops with proper clearance holes at each wall intersection are also required for most through wall chimney runs. Proper firestopping seals off living spaces, attnics, and concealed spaces to control fire spread.
Prep Work and Framing
Cutting Wall Openings
Once you have all the venting components and materials needed, the first construction step is cutting openings in the interior and exterior wall. The holes should be slightly larger than the outer diameter of the wall thimble, usually 8-10 inches depending on pipe size. Cut the interior hole centered at the planned pipe route. For exterior holes, cut a hole large enough to accommodate either a round termination cap or rectangular wall housing.
The framing around the thimble opening will need to be built out with additional studs to provide structural support. Consult your thimble instructions for required framing dimensions.
Securing the Wall Thimble
With the openings cut, secure the thimble centered in the wall opening using pipe straps or metal fasteners. Maintain 1 inch of clearance all around the thimble to framing or other combustibles. Do not fill this air gap with any insulation or sealant. High-temp silicone or metal tape can be used to seal the thimble to sheathing or exterior wall surface. The thimble should be angled downward slightly to allow any condensed moisture to drain outside.
Firestops serve a critical role in sealing combustible wall cavities and preventing fire spread. For straight through wall penetrations, firestop spacers need to be secured at each wall intersection, attic level, and ceiling level. Offset pipes with elbows require an additional firestop at every intermediate point where the pipe routes through framing.
Firestop installation involves cutting an opening for the vent pipe and packing any gaps with firestop caulking. The firestop spacers maintain proper clearances and support the pipe. Rigid fiberglass sheets can provide additional fireproofing between framing and the vent pipe if space allows.
Installing the Chimney Pipe
Connecting Pipe Sections
Once thimble and firestops are in place, the stove pipe sections can be installed by snapping male and female ends together. For double wall stove pipe, the inner and outer pipe segments connect separately. Apply high-temperature sealant at each joint to prevent leaks.
Use adjustable length sections to bridge offsets around framing or elbows. Elbows and tee fittings connect the pipe at interior or exterior corners. Support straps screwed into framing secure the pipe in place approximately every 3 feet. Allow a little room for expansion and contraction from heat.
Maintaining Proper Clearances
Maintaining the 1-inch clearance around the pipe is critical for any sections that pass through combustible framing. Keep pipe from directly contacting wood or insulation by using offset support brackets and spacers. Where needed, sheet metal shields attached to framing provide additional protection of combustibles.
Make sure interior pipe has recommended clearance from ceiling. At the thimble, the pipe should align nearly centered so heat dissipates from all sides into the chimney chase.
Securing and Supporting the Pipe
Adequately supporting the venting system keeps the pipes stable, centered, and maintains clearances. Install listed securement straps or supports at least every 3 feet along horizontal pipe runs. Vertical supports are typically at 10-foot intervals. Allow for some flexibility to accommodate thermal expansion of pipe joints.
There are several support system options:
- Riser supports attached to the wall
- Wood framing secured with metal fasteners
- Suspended supports from ceiling joists
- Floor standoff frames above the pipe
Choose a durable support system that keeps the vent pipe properly positioned through its full run.
Sealing Interior and Exterior
Sealing the venting system from the indoors and outdoors is important for both weatherproofing and firestopping. Use high-temp caulk to seal gaps between wall framing and interior pipe sections where they intersect. Maintaining the vapor barrier with insulation will help reduce cold air infiltration.
For exterior pipe sections, apply waterproof silicone caulk around outer wall penetrations. Flashing should be installed to divert rainwater from the pipe exterior. Finally, finish the exterior wall surface around the pipe with weather-resistant materials to match the siding.
Completing the Installation
Installing the Termination Cap
The final step is installing the vent termination cap on the pipe end exterior to the home. Galvanized steel or stainless steel caps are durable options. The cap should have a wire mesh screen to keep out birds and debris.
For straight through walls, a vertical cap directed away from the home is preferred. Offset pipes will need a horizontal rain cap. In all cases, the cap should maintain minimum code clearances from windows, doors, and other openings.
Inspecting the Installation
After completing the vent installation, thoroughly inspect the full assembly. Check that proper clearances from combustibles have been maintained and firestops properly seal framing cavities. Confirm supports are securely fastened and pipe joints are tight.
Test draft by starting the stove to ensure adequate ventilation directs smoke up through the chimney system. A qualified professional should inspect and confirm the system is properly installed before using.
Checking with Local Building Codes
Most jurisdictions require permits and inspections for through the wall stove vent installations. Research local regulations and meet any requirements before proceeding with your project. Schedule an appointment for the authority having jurisdiction to come out and confirm your installation meets code.
Obtaining final approval is essential before actually using your newly vented stove to prevent fire or carbon monoxide risks from potential violations.
Maintaining Your Wall Vent System
Proper maintenance is necessary for peak performance and safety of your wall-vented wood stove. Inspect the full exterior portion of the venting system periodically. Look for any damaged or deteriorated sections, or areas where water is infiltrating around seams and seals. Repair any damaged caulk or protective finish materials.
Also check vent interiors regularly during cleaning for creosote buildup or obstructions which could inhibit draft. Scrape or brush away any accumulated creosote and remove debris or animal nests found in the cap.
The supports, pipe sections, thimble and elbow connections should be inspected yearly and tightened or repaired if any looseness from shifting or vibrations develops over time. Keeping your wall pass-through system properly maintained will provide years of safe and efficient heating.
Venting a wood stove through the wall can enable placement options not possible with conventional interior chimney venting. But this type of installation has special considerations for structural support, firestopping, weather sealing and clearances. Following the guidelines provided in this walkthrough will allow you to plan and execute your wall pass-through venting project successfully and safely.
Pay close attention to properly sizing and securing the wall thimble, maintaining clearances, and installing firestops. Be sure to seal all interior and exterior penetrations and check local building codes. With careful planning and attention to detail, your innovative wall venting system can provide an ideal heating solution.