What actually breaks on a chimney

The crown, the mortar joints, the brick face and the flue tile. In that order, most weeks.

The crown is the concrete slab on top of the stack. It sheds water away from the flue. Thin ones crack, and most crowns poured before the 1970s are thin. Once water gets past it, the whole chimney starts working against itself.

Mortar goes next. Rain soaks into the joints, sun bakes them, and the mix slowly turns to sand. You can usually scrape it out with a screwdriver by the time anyone calls us.

Then the brick face starts spalling, which is when the outer skin pops off in flakes. That is water that got in, froze or expanded, and pushed its way back out. Cosmetic at first. Structural if it keeps going.

Flue tile is the one nobody sees. Clay splits from heat and from earthquakes, and once it does the chimney is no longer sealed. That damage sits fifteen feet up and only a camera finds it.

How we work out what needs doing

A Level II inspection, because guessing at masonry from the ground is how people pay for the wrong repair.

Plenty of chimney repair calls start with a stain on a ceiling or a bit of loose brick in the yard. Neither tells you where the problem is. Water shows up a long way from where it got in, and loose brick on the ground can mean a failing crown or nothing much at all.

So the camera goes up before the quote comes out. You see what we see, and the repair matches the actual fault.

More about Level I and Level II inspections.

Repairs we do most

1. Crown repair and rebuild

   Patching hairline cracks, or pouring a new crown with a proper overhang and drip edge when the old one has gone.

2. Tuckpointing

   Grinding out failed mortar and repacking the joints. Done right it lasts decades. Done as a smear over the top it lasts one winter.

3. Brick replacement

   Cutting out spalled or cracked units and matching what is there. Older LA brick takes some hunting.

4. Firebox repair

   Refractory mortar and firebrick where the gaps have opened up behind the grate.

5. Flashing and waterproofing

   Resealing where the chimney meets the roof, then a breathable sealant on the masonry so the brick stops drinking.

Los Angeles is hard on masonry

Earthquakes crack it and coastal air eats it, and neither shows up in the living room until it is well along.

Northridge in 1994 split flue tile across the basin. Lots of those chimneys got a crown patch and nothing else. Every quake since has added to that.

Near the water it is salt. It works into the mortar and pulls it apart from inside, which is why beach city chimneys need pointing on a shorter cycle than inland ones.

And then there is sun. Two hundred days a year of it bakes the moisture out of masonry that spent the winter soaking wet. That cycle is what turns a hairline crack into a repair.