Looking for a little help on a chimney repair. I went up to re-point the mortar and the first 10 courses of brick were crap so I took them off. they’ve been de-mortared and power washed ready for replacement. I’ve already re-mortared the lower levels of brick and will give them a few days to set up.
My question is how to go about applying the crown. All the pictures I’ve seen show the mortar hard against the tile flues but my understanding is that the flues are supposed to float independent of the brickwork.
Do I make a metal form around the flues and mortar a beveled edge to that and then caulk the top to the flues?
Is it necessary to extend the top layer of brick out as a drip edge? I don’t see where a little water running off the top is going to matter if it’s raining. It’s all going to get wet.
Prior to installing the masonry crown, I would apply a polyurethane caulk at the base of the flu tile where it enters the chimney. Once cured, install the crown. On the flu metal flashing, installing this in addition to the caulk might be more of a belt and suspenders approach but I can’t see the harm in it. Just be sure to use ample caulk at the upper vertical edge of the flashing: otherwise, water will seep through.
I recommend a drip edge for the top course or two of brick because this will redirect runoff water from the crown away from the chimney sides which in turn reduces the amount of water running down the chimney onto the chimney step and/or counter flashing thus reducing another potential leak source.
I was going to use the flashing as a form to keep the mortar off the tile but I’ve since read about using corrugated cardboard as a temporary spacer (oiled on the cement side). I’ve got a gap problem to deal with.
I was thinking of building the brickwork straight up and mortaring in a metal drip edge. This would be to save time and avoid moving the bricks further away from the tiles since it’s not a very close fit to begin with. There’s a good inch of space between tile and brick now and overhanging bricks 1 1/2 inches would add considerably to this gap.
Have you ever seen drip edges mortared into place? Also, the gap between the 2 tiles is 1/2 in which makes it tough to get a sealant into because of the amount of tile that sticks up. I suppose I could add another row or 2 of bricks.
Last question, are the flue tiles mortared to each other/ I pulled the top ones off as if they were just stacked in place.
A masonry drip edge is simply more aesthetic but I understand your issue with increasing the gap at the flu tile. I have never seen metal drip edge mortared like that but see no harm because it will serve its functional purpose. The only issue I see might involve someone working on or around the chimney at a later date and possibly denting the metal inward eliminating its ability to drip water away from the chimney side.
One way that might allow you to use a masonry drip edge involves a different way to install the top course of brick. If you want say, a 1/2" overhang for the drip edge, simply proportionally increase the width of each mortar joints at the top course so as to accomplish this. Depending on the size of the chimney, this may increase each mortar joint by an 1/8" or so. Whatever overhang you decide upon, I would never extend the drip edge more than about 25% to 30% of the width of the brick.
The flu tiles should be mortared at the joint and I suspect your tiles seem to easily come apart because they were either improperly mortared or the old mortar simply died. Use a high temp mortar much like the mortar used at the firebrick in the firebox. An unmortared flu tile is an invitation for hot gases to escape.
Dereknocue67, thanks for the information. I was a little apprehensive about doing this but after seeing a number of chimneys that were not built or flashed correctly I’d rather do it myself.
I’ve got the chimney bricked up and flue tiles mortared back in place. I’ve decided to go with a cement crown with a an overhang but I’ve got conflicting answers to the product used. I’ve been told to pour a pure portland cement type I/II. Is there an advantage to a pure cement versus a concrete mix?
Did you get a permit to do the chimney work? Most locales have specific regulations regarding chimneys, due to the safety issues, and require a sign off by an inspector.
I can’t find the source for this, but I recall the pure cement is more flexible and can handle the temperature differential better. The concrete mix might be expected to contain sand, and less lime. I think this is one of the basic differences between mortar and concrete mixes.
Good luck with this though. I plan to install a stanless steel liner in my chimney soon, and I might have to do repair work on the crown too. But they have all sorts of top plate designs to minimize the flashing requirements.
That would explain why I was told to use just cement on the crown. It’s not doing anything structurally other than keeping water off the bricks. If I had the bucks I would have ordered a 2 piece stainless steel system that keeps the water off and screens out the flues. But at $9 for a bag of cement plus some scrap wood for a form I have to let unemployment make that call.
I have a gas fireplace and the flues looked pretty good going down but I didn’t see a way of putting a liner in from above without some kind of flexible tubing. It’s not a straight shot down to either the furnace or the fire place.
both modern mortar and concrete contain fine aggregate (sand) and cement. concrete may have coarse aggregate (stone and gravel) thought for a cap it wouldn’t.
old mortar might be lime and sand.
modern mortar might contain equal lime and cement to make it sticky.
The liners are flexible to some degree. For my chimney, the flue to the furnace is almost straight down. I don’t know how flexible they are though. I plan to talk to someone who’s actually installed one before I start. Most of my problems are at the bottom of the chimney with cracking in the liner tile. I figure the SS liner is the easiest way to stay safe.