Rebuilding a chimney that is past repointing

Mortar joints are meant to be the sacrificial part of masonry — the National Park Service describes a good repointing job as lasting 30 years and often much longer, after which the joints are done again. Brick is not sacrificial that way. Once the hard outer skin of a brick has spalled off, the soft core underneath drinks water freely, and no amount of new mortar around it puts that skin back. Chimneys reach that point sooner than the walls below them: wet on five sides, slow to dry, and in the Puget Sound area doing it through a long wet season.

• Cracks through the bricks, not just the joints. The Brick Industry Association treats cracks running through multiple brick units, stepped or diagonal cracking, and cracks wider than about 2 mm as structural signals rather than maintenance items.
• Out-of-plane movement. A stack that leans, bows, or has shifted courses is no longer doing its job by geometry. Repointing a leaning chimney leaves it leaning.
• Widespread spalled brick. Scattered spalled units are cut out and replaced individually. When most of the exposed faces have gone, there is nothing left to point to.
• Damage below the visible masonry. Cracked or collapsed flue tiles, tiles with chunks missing, or a damaged smoke chamber change the job entirely, because the repair has to reach them.
• The mortar is gone, not eroded. Repointing needs sound mortar to cut back to. Where joints are voided through the full thickness of the wall over most of the stack, the units are no longer bedded on anything.

A rebuild is defined by one number: the line demolition stops at. Everything above it is new, everything below it stays, and choosing it is the whole decision. It is set by finding where sound, well-bedded masonry actually begins — not by picking the cheapest stopping point.

Above-the-roofline rebuild

The exposed portion is taken down to just below the roof line and rebuilt from there. This is the common case, because the exposed stack takes almost all of the weather and the interior portion is usually intact.

Rebuild to the smoke chamber

The smoke chamber is the tapered masonry funnel above the firebox that gathers smoke into the flue. Taking the chimney down to its top means the entire vertical run above the fireplace is new.

Full rebuild

Demolition continues below the roof to a floor line or to the foundation, and the chimney is rebuilt upward from there, tied into the structure at each level it passes.

Conversion or removal

Instead of new masonry above, a listed factory-built metal chimney is carried up from a transition at the smoke chamber — or the chimney is taken down, capped, and retired from use.

An unreinforced masonry chimney is brick laid up with mortar and nothing else — no steel running through it, no straps tying it to the house. That is how nearly every older chimney in the region was built, and it is why a chimney is treated as a seismic problem and not only a weather problem. The Background section of Seattle's Director's Rule 07-2025 says unreinforced masonry chimneys are extremely vulnerable to earthquake damage because of their height, weight, and weak structural connections, and may collapse in even a minor earthquake.

That is what makes a rebuild different from the chimney it replaces. Seattle is assigned Seismic Design Category D2 in the residential code, which triggers reinforcement and anchorage: continuous vertical bars anchored into the foundation, ties enclosing that steel, and straps anchoring the chimney to floor, ceiling, or roof framing more than 6 feet above grade. Grout is kept from bonding to the flue liner so the liner can still move as it heats.

Repointing a chimney in Seattle needs no permit provided nothing structural changes — SDCI says so in its own homeowner guidance. A rebuild is a different animal, and Director's Rule 07-2025 states that a building permit is required for unreinforced masonry chimney work, with narrow exceptions for minor patching and low-value work. Outside Seattle, jurisdictions in King, Snohomish, and Pierce counties enforce the Washington State Residential Code with their own amendments and their own permit desks.

1. 1

   Confirm which jurisdiction governs

   Seattle's Director's Rule applies inside the city. A house in Bellevue, Everett, or Tacoma is under its own building department, and the answer can differ.

2. 2

   Settle the design path

   Seattle's rule offers an engineered design by a registered design professional, a prescriptive design available for chimneys less than 12 feet tall above the roof line, or removal of the chimney. A taller chimney can sometimes be reduced in height to bring it into the prescriptive path.

3. 3

   Apply, with the scope attached

   The permit application describes what comes down, what goes back, and how the new work ties to the old. The standard details belong to the permit set, not to a sales sheet.

4. 4

   Build to the approved detail

   Where new reinforced masonry meets the existing chimney, Seattle's rule expects either new bar dowelled into the existing masonry or its own concrete bond beam detail at the transition.

5. 5

   Call the required inspections

   Seattle's rule requires calls to SDCI when demolition is complete and repair is ready to begin, before concrete is placed for a bond beam where that detail is used, and when the work is finished. Scheduling those is the contractor's job, not yours.

On an older house the rebuilt stack has to look like it belongs. Sound units from the demolished masonry can often be cleaned of old mortar and reused on the visible faces, with new brick kept to the back and inside. Units that have already lost their face are not salvage — they are the reason for the rebuild.

Where new brick is needed, matching means physical properties as well as color, texture, and size. The Brick Industry Association classifies brick by resistance to freezing when wet, and brick that will be wet and freezing is specified to the severe weathering grade — demonstrated by 50 freeze-thaw cycles, or by strength, absorption, and saturation limits. A brick chosen only for color is chosen halfway.

Mortar follows the same logic in reverse: stronger is not better. Both the Brick Industry Association and the National Park Service hold that mortar should be no stronger than the units around it and no harder than the mortar it meets, because stress a soft joint would relieve gets driven into the brick instead, cracking and spalling it. Reinforcement and grout carry the structure in a rebuilt chimney; the visible joints still have to be compatible with the masonry and tooled to a profile that sheds water.

A rebuild is the one moment when every component at the top of the chimney is accessible at once. Leaving any of them for later means going back up later.

• Termination height. The rebuilt stack has to finish at least 3 feet above the point where it passes through the roof, and at least 2 feet above any part of the building within 10 feet. This is the geometry that sets how tall the new masonry is.
• Flue lining. A masonry chimney is required to be lined with material suited to the appliance connected to it. A rebuild that stops at the brick and reuses a cracked tile liner has solved the visible half of the problem.
• Crown or cap slab. The code calls for a concrete, metal, or stone cap sloped to shed water, with a drip edge and a caulked bond break around the flue liner so the liner can expand independently of the slab.
• Rain cap. A cap over the flue opening keeps rain and animals out of a flue that is otherwise a vertical drain. Where a spark arrestor screen is used, the mesh sizing and free area are specified by code.
• Flashing and counter flashing. Roofing is disturbed by an above-the-roofline rebuild, so flashing is reset rather than smeared over. Counter flashing is let into a mortar joint roughly three quarters of an inch to an inch deep and mortared in, not surface-glued.
• A cricket where the geometry calls for one. A cricket is the small peaked structure behind a chimney that splits water around it. Code requires one where the chimney dimension parallel to the ridgeline is greater than 30 inches and the chimney does not intersect the ridge.

You get a written scope and price before work begins, and nothing starts until you approve it. On a rebuild that document is doing real work, because two bids that both say "rebuild chimney" can differ by most of the chimney. Read it for these.

1. The demolition line, stated in a way you can point at. "To 12 inches below the roof sheathing" or "to the top of the smoke chamber" — not "as needed".
2. What happens if worse conditions appear below that line. How a change is priced and approved before it is built, rather than discovered on the invoice.
3. Brick and mortar specification. Whether existing units are being salvaged and how many, the weathering grade of any new brick, the mortar type, and the joint profile the stack will be tooled to.
4. Reinforcement and anchorage. The vertical steel, ties, straps, bracing points, and the transition detail where new work meets old, matching the approved design.
5. Liner make, model, and size. Which lining system is going in, sized to the appliance it serves, and whether it is insulated.
6. Crown, cap, flashing, and cricket. Named individually with materials, so nothing quietly falls outside the price.
7. Permit, inspections, and who calls them. Which permit is being pulled, by whom, and which inspections the contractor schedules.
8. Protection, debris, and site condition. How the roof, gutters, landscaping, and interior are protected, and how demolition debris leaves the property.
9. The photo record. Before and after photographs from the same angles where practical, including the conditions found once demolition exposed them.