Water – Chimney still leaking despite reflashing and coating

chimneyleakroofwaterproofing

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 north west US area.

Update

Here is the picture inside the attic. 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.

[![enter image description here][2]][2]

Outside

[2]: https://i.stack.imgur.com/323ma.jpgenter image description here

Best Answer

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.

Related Topic