Wood Stove Installation: From Hearth Pad to Chimney Cap

Choosing a Location

Location determines everything. A bad choice means fighting every constraint through the whole installation.

The ideal location:

• Central to the space you want to heat — stove heat radiates outward, it does not travel through walls
• Near an exterior wall, which simplifies the chimney run (single-wall penetration)
• Away from high-traffic areas where people will brush past the stove
• Where the chimney can exit through the roof with a straight, vertical run — every horizontal offset and elbow reduces draft

What to avoid:

• Locations where the chimney must pass close to ceiling joists, roof structure, or existing insulation (each penetration is a fire risk if done improperly)
• Corners that trap heat and reduce air circulation around the stove
• Rooms without sufficient combustion air — a tight modern house may need an outside air kit

Walk the path from the stove floor to the exterior sky in your mind before you start. The straighter and shorter that path, the better your chimney will draw.

Hearth Pad Construction

The hearth pad protects the floor beneath and in front of the stove from radiant heat and falling coals.

Minimum dimensions: The pad must extend a minimum of 18 inches in front of the loading door and 8 inches on all other sides. If the stove has legs less than 6 inches tall, extend the front clearance to 24 inches.

Material options:

| Material | R-Value Note | Ease of Install | |---|---|---| | Concrete board + tile | Standard — meets code | Moderate | | Full-thickness brick on non-combustible substrate | Exceeds standard | Moderate | | Pre-made hearth pad (steel frame + tile) | Quick install, verify listing | Easy | | Poured concrete | Excellent, heavy | Difficult |

For a tile-on-concrete-board pad:

Stovepipe Sizing and Run

The stovepipe connects the stove collar to the chimney. Most stoves use 6-inch or 8-inch single-wall black stovepipe for the interior run.

Rules for the stovepipe run:

• Minimum 18 inches from combustibles (wall, ceiling, trim) with single-wall pipe. Reduce to 6 inches with proper heat shield.
• Maximum 75% horizontal to vertical ratio — you want mostly vertical
• No more than two 90-degree elbows in the run
• Every horizontal section must slope upward toward the chimney at a minimum of 1/4 inch per foot (prevents condensate pooling)
• All joints must overlap at least 3 inches, with the upper pipe telescoping over the lower (male into female going upward)

Fastening: Secure every joint with three sheet metal screws. Do not skip this. Hot gases under draft pressure will separate unsealed joints and fill the room with smoke.

Clearance to ceiling: Where the stovepipe passes through the ceiling into the insulated chimney section, use a listed ceiling support box rated for your pipe diameter. This provides structural support and maintains clearance from combustibles at the penetration point.

Chimney System

The chimney must be a listed, labeled system designed for solid fuel — specifically Class A (HT) chimney rated for 2100°F. This is not a suggestion. Standard metal chimney intended for gas appliances is not rated for wood burning temperatures and will fail catastrophically.

The basic chimney assembly from ceiling to sky:

1. Ceiling support box (provides structure and maintains clearances through ceiling)
2. Insulated chimney sections (typically 2-foot lengths of double-wall or triple-wall pipe)
3. Firestop spacer at each floor and at roof penetration
4. Flashing at the roof penetration
5. Storm collar directly over the flashing to seal around the pipe
6. Chimney cap on top

Sizing: Match the chimney diameter to the stovepipe diameter. Never reduce diameter going up — the transition must stay the same size or increase. A 6-inch stove collar uses 6-inch chimney.

Through-Roof Penetration

This is where most installation errors happen.

Clearances at Roof Penetration

The chimney must clear the roof structure on all sides. In a framed wood roof, every framing member is a combustible. NFPA 211 requires a minimum 2-inch clearance from the outer chimney surface to any combustible material. Most listed ceiling support boxes and firestop spacers are designed to maintain this automatically when properly installed.

First Fire and Curing

Do not build a full fire on day one.

New stove paint, high-temperature sealants, and manufacturing residues need to cure gradually. Skipping this step will fill your house with acrid smoke and may crack the cast iron or steel if thermal expansion is too rapid.

Curing procedure:

• Day 1: Small kindling fire only. Allow to burn for 30 minutes, then let cool completely. Open windows.
• Day 2: Slightly larger fire. 45 minutes, full cool.
• Day 3: Normal small fire. From day 4 onward, normal operation.

During curing, check every joint in the stovepipe for smoke leaks. Light a stick of incense and hold it near each joint — any air movement pulling the smoke toward the joint indicates a gap that needs sealant or tightening.

Draft Problems

A new installation that does not draw well is usually one of three things:

Cold chimney: A cold, unprimed chimney fights you. On the first fire of the season, hold a burning piece of paper up into the firebox (door open) to warm the flue before loading fuel. Once the flue warms and draft establishes, add kindling.

Too many offsets: Each 90-degree elbow degrades draft. If your installation has more than two elbows, you may have chronic draft problems. This is a design problem, not a fixable symptom.

Chimney too short: A chimney that barely clears the roof is subject to wind downdrafts. Extend by adding sections. The 2-10 rule is the minimum — taller is better for draft.

Annual Safety Checklist

Install a wood stove and your annual maintenance starts immediately.

• Clean the chimney before each heating season (see the chimney cleaning article)
• Inspect all stovepipe joints for looseness, rust, or separation
• Check the hearth pad for cracked tile or loose sections
• Inspect the chimney cap — birds and squirrels nest in uncapped chimneys in summer
• Test door gaskets by closing the door on a dollar bill — if it pulls out easily, the gasket has compressed and needs replacing
• Check the firebox and baffle plate for cracks

A properly maintained wood stove installation will outlast the house.