Fireplaces, Heating Stoves, Flues and Chimneys - Type of lightweight mortar?

I'm needing to replace mortar on chimney crown. Too many cracks/areas where water can penetrate. Just wondering if there's a lighter product than regular mortar or a better product to replace mortar. Any suggestions?

Depending on your existing chimney construction, you may be able to purchase a precast concrete unit with a proper overhang and drip (not very likely).

Why would you want a lightweight mortar cap?

Dick

I need something lightweight because the crook who sold us the house just had a plywood cover going over the brick, with flue hole cut out. The flue sits up high enough, and we have a gas log unit installed, so it won't catch fire. Problem is that if it rains heavily it pools and bounces off the flat plywood cover into flue and down chimney...dripping in fireplace. No much dripping, but enough to be annoying. Plywood is ok, so I just want something not as heavy to build a sloping cover so water won't pool and cause leaks.

Update...got on the roof yesterday and saw there was less than 1 inch of flue protruding out above the plywood cover. No doubt with the hard rains, water was pooled and splashing down the flue. I'm going to get a gallon of tar and basically cover all the plywood, with about a 1 inch gradient from the flue down to the sides. Not a problem...just needs to stop raining so I can do it!

That would be considered a short term repair and not really desireable.

You flue should be extended and a proper crown or lid used that will extend beyond the edge of the chimney to prevent water from entering and causing moisture problems like stains and mold. You should also have a chimney cap to leep out water and critters that can cause back-ups and fires.

The condition of the chimney indicates a high probability of other problems. If you don't correct them soon, iy could lead to more expense. If you go to sell a good home inspector will easily spot the situation and you wil end up paying more, especially if it leads to other areas.

Dick

You do not need lightwieght mortar, you need a real chimney cap:

http://www.capbrick.com/proper_brick_construction.htm