Outdoor fireplaces - the heaviest thing in the yard

What is outdoor fireplace installation?

An outdoor fireplace is a chimney-vented masonry structure with a firebox, a throat and a flue that carries smoke up and away. Unlike a fire pit it is directional - it warms and faces one seating area rather than a circle - and it is tall and extremely heavy, so it needs a designed footing rather than a compacted base. Most of the cost and nearly all of the risk sits in two invisible places: what it stands on, and whether it drafts.

Signs you need outdoor fireplace installation

• You want an outdoor room with a focal point and a wall, rather than an open circle of seats
• Wind constantly blows smoke from an open fire across the seating, and you want it vented upward instead
• You are enclosing or defining one edge of a patio and want the structure to do that job as well as the fire
• You want a fire feature that can sit under or beside a covered structure, which an open pit usually cannot
• An existing outdoor fireplace smokes back into the seating area, or has cracked masonry and a leaning stack
• You are building a full outdoor living space and want a hearth as the anchor rather than an afterthought

Seeing something not on this list? Browse hardscaping problems by symptom →

How outdoor fireplace installation actually works

1. 1

   Design, permit and - commonly - an engineered footing detail

   Outdoor fireplaces are tall structures with high, concentrated dead loads, and most jurisdictions permit them. In many places the footing design has to be produced or reviewed by an engineer, and seismic and wind considerations apply in some regions.

   Watch forA fireplace proposed with no permit and no footing detail. This is a heavy vertical masonry structure. A contractor treating it as a large barbecue has misjudged what it is.

2. 2

   Excavating and pouring the foundation

   The footing goes below the local frost depth where that applies, is sized for the mass above it, and is usually reinforced. Everything about the fireplace's life depends on this and none of it is visible afterwards.

   Watch forA footing poured on the same base as the surrounding patio, or one placed at patio depth in a freezing climate. Differential frost movement under a tall structure is exactly how a chimney ends up out of plumb.

3. 3

   Choosing site-built masonry or a modular firebox system

   A fully site-built firebox and flue is traditional masonry work. A modular or manufactured firebox and chimney system is engineered as an assembly, comes with listed clearances and installation instructions, and is then clad to look like masonry. Both are legitimate; they are inspected against different criteria.

   Watch forA manufactured firebox installed outside its listing - wrong flue, wrong clearances, wrong cladding detail. The listing is what makes it safe and what the inspector checks it against.

4. 4

   Building the firebox with materials rated for it

   The firebox interior is built in firebrick set in refractory mortar, or is the manufactured unit itself. Ordinary masonry units and ordinary mortar are not intended for sustained direct fire exposure and will deteriorate.

   Watch forStandard mortar used inside the firebox. It degrades under heat, the joints open, and eventually you have a fire behind the firebox rather than in it.

5. 5

   Throat, smoke chamber and flue - the parts that make it draft

   Whether an open fireplace draws smoke up the chimney or spills it into your face is determined by the geometry of the opening, the throat and the smoke chamber, and by the flue size and height relative to that opening. These relationships are set by code and by long-standing masonry practice.

   Watch forAn opening enlarged for looks after the flue was sized. A wide, tall, handsome opening on an undersized flue is the single most common reason a finished outdoor fireplace smokes, and correcting it afterwards is close to a rebuild.

6. 6

   Chimney, height, cap and surroundings

   The stack has to terminate high enough, and far enough from obstructions and nearby roofs, to draft reliably. A cap keeps rain out of the flue and a spark arrestor is required in many areas, particularly in wildfire-prone regions.

   Watch forA chimney terminated low because the client wanted a shorter stack, or sited where the house roof and prevailing wind create downdraft. Both produce a fireplace that works on calm days and smokes on the days you want to use it.

7. 7

   Gas, if included, and the hearth extension

   Gas logs or a gas starter mean a licensed gas fitter and a permitted line. In front of the opening, a non-combustible hearth extension protects the surrounding surface from embers and radiant heat.

   Watch forA wooden deck or combustible surface running right up to the firebox opening. Hearth extension requirements exist because embers land there.

8. 8

   Cladding, curing, inspection and first fire

   Stone veneer, brick or stucco goes on the structure, the mortar and any refractory work is allowed to cure, and the installation is inspected. The first fires are built small and gradually to bring the masonry up to temperature.

   Watch forA full fire in freshly built or freshly repaired masonry. Rapid heating of green mortar or a damp firebox causes cracking, and the damage happens on day one rather than showing up later.

What does outdoor fireplace installation cost?

An outdoor fireplace is the most expensive common hardscape feature, and the footing, the firebox and the flue are the bulk of it rather than the visible stone. Site-built masonry, a manufactured firebox system, and any gas connection all price very differently - compare like for like.

See the full outdoor fireplace installation cost guide - by material, size and region →

If the number is the problem, here are the ways people pay for it →

Outdoor living budget and planning tools → Scope the project before you take quotes on the most expensive feature in the yard.