My chimney was leaking and the contractor pulled apart the roof around it and reput it with proper sealing and coating. Then he also coated the entire chimney with Geocel siliconized seal which is supposed to be best but we got slow ran for last 8 hours and to my surprise the chimney is still leaking.

Examining the leak in attic, the breaks of chimney are all wet and there is slow dripping from several points all around chimney.

So how could the water still get in?

My contractor will follow up but he even he probably doesn't know for sure what's going on. Any hints?

This is northwest US area.

The dark shade is the wet area. This was take earlier, now almost the entire wall is wet and dripping slows from different points. It's like 1 drop every 5 seconds or so. I don't have picture from outside but its very glossy now after we coated it.

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  • 1
    We once had water leaking in through cracks in the top of the chimney, around the flues. Had to have the chimney cap chipped away and recast. Can you get a picture of the top of the chimney?
    – Mark
    Dec 14, 2019 at 16:54
  • Is this a new leak from something happening or is it an old leak being repaired?
    – Jack
    Dec 14, 2019 at 17:43
  • @Jack I updated post with picture. This leaks seems to be old before we moved into the house and I am aware of it for like two years. I had put buckets to have it under control now time to fix it.
    – zar
    Dec 14, 2019 at 18:00
  • It appears the roof is sloped away from the chimney, so presumably there is no chance for rain to get in but only at the chimney and flashing. Please confirm. If so is the flashing set into a groove cut into the masonry joint or just secured flat to the brick and caulked at the top?
    – Jack
    Dec 14, 2019 at 19:07
  • 4
    Ok there is step flashing on the sides but the horrid mess at the top of each flashed section makes me think it is not a “Z” where the top edge is embedded in the mortar, this looks like a ham fisted repair in my opinion but it is not well focused. With these photos the only place I would be looking is at the cap for cracks and at the flashing top at the chimney (sorry that just looks like crap even out of focus) the other area I was thinking is not an issue with your roof lines.
    – Ed Beal
    Dec 14, 2019 at 23:28

2 Answers 2


Water gets into a chimney by one (or more) of five ways:

  1. Via the actual opening of the flues Yours have metal covers, so this is probably okay.
  2. Via missing, cracked or deteriorated flaunching on the top of the chimney This is very common as the mortar has a very hard life. Your right side flue isn't sitting vertical which means it's dropped and unlikely to have a good seal to the flaunching.
  3. Via the brickwork itself. Mortar erodes to the point where perpends or cross joints are non existent. Water can run in and down such erosion. Difficult to tell what condition your is in from the pic. Plus the chimney is a poor design with very little oversailing to throw the rainwater away from the main body of the walls.
  4. Via the brickwork to roof connection Usually metal flashing. Your's look to be in a bit of a state, repair on top of repair is unlikely to be effective. Plus, it looks like the long horizontal section looks to be in one piece. If this is lead then it's almost certainly cracked. Max length for lead is around 1.5m usually. Thermal expansion and contraction will crack long lengths of this 'thin' lead.
  5. The roof material adjacent to the chimney Very common for tiles etc. to be broken underneath the metal flashing etc. They never get replaced as the flashing makes this difficult. Heavy handed installation of flashing often leaves tiny cracks in the tiles which form into full splits over time due to weather (hot/cold/frost etc.)

My best guess is the flashing wasn't great to start with and the repairs haven't been effective. Plus the top flaunching needs to be in one piece. If it is the flashing you might find that the waterproof sealing of the brickwork has made leaking worse, by the simple fact that the water now runs straight off the brickwork surface and onto the ineffective flashing in greater quantity. Brickwork naturally soaks up a certain amount of water and naturally evaporates the same in dry weather.


Use a crown coat sealant and a brick waterproofer spray. Your chimney brick is absorbing water. Your chimney crown is letting water in.

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