Chimney Leak Repair Cost Calculator
A leak is water finding a way in at the crown, cap, flashing or porous brick. Price the fix — but find the real source before you seal anything.
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A leaking chimney is usually water getting in at the crown, the cap or the flashing, or through porous brick. A cap, a crown seal and a breathable water repellent are the common fixes — about $660 here. Find the source before you seal.
A leaking chimney is not one problem — it is water winning at whichever point is weakest. The usual suspects, roughly top to bottom, are a cracked crown, a missing or rusted cap, failed flashing at the roof joint, and porous or spalled brick that wicks water straight through. The cheap mistake is to slap a sealer on the brick and hope; the leak just re-appears from the real source above.
So the order of operations matters more than the price. Find the source, fix that, then waterproof. A common belt-and-suspenders package is a crown seal, a new cap and a breathable water repellent on the brick — this tool totals that package, but it is worth pricing the crown, cap and flashing tools individually once you know which one is actually failing.
Formula
The package total is a simple sum with a cushion:
total = (waterproofing + cap/crown seal + labor) × (1 + contingency)
If the diagnosis points to one culprit — say, only the flashing — use that dedicated tool instead of the whole package.
Worked example
A chimney weeps after every storm. The plan: a breathable repellent on the brick ($210), a crown seal plus a new stainless cap ($265), and $320 labor for the roof visit. Because the source is not yet certain, you carry a 12% contingency in case the flashing turns out to be the culprit too:
(210 + 265 + 320) × 1.12 = 795 × 1.12 ≈ $890
If a hose test pins the leak on the flashing alone, you would drop the repellent-and-cap package and price a reflash instead — cheaper and actually on target.
Find the source before you seal
- Do a hose test. With a helper inside, wet one component at a time — flashing, then crown, then brick face — for several minutes each until the leak shows. Guessing wastes money on the wrong fix.
- Never seal a wet or cracked crown. A sealer over damage traps water. Repair the crown or flashing first, let it dry, then apply a breathable repellent.
- Use a vapor-permeable repellent, not a film. Masonry needs to breathe. A film-forming “waterproofer” can trap moisture and cause spalling; a breathable silane/siloxane repellent sheds water while letting vapor out.
- Rule in the cap. A missing cap lets rain straight down the flue — often the simplest, cheapest fix of all.
Reference table
The three water-entry points to price individually once you know the source — labeled planning bands for each:
| Masonry job | Typical planning band |
|---|---|
| Chimney flashing repair | $200–$1,500 |
| Crown repair / replacement | $200–$3,500 |
| Chimney cap install | $150–$600 |
These are labeled planning bands — a reality check on a written quote, never a price you should expect to pay. Chimney cost swings with roof access and scaffolding, chimney height, roof pitch, how far the damage runs and local labor. Enter the real figures from your itemized quote above, and get that quote from a CSIA-certified sweep and a licensed, insured mason.