I recently reroofed a house with asphalt shingles for a neighbor, who now wants to spiff up his cement-block chimney that vents only a pellet stove–just the portion above the roof deck, about 6′ high. I suggested cultured stone.
My question is how to install the stone in the [aluminum] flashed area. Does one wrap the block with diamond lath all over? And does the stone sit tight on top of the shingles, making eventual re-roofing difficult? If not, doesn’t the air gap look odd? Or is the veneer re-flashed into the shingles (perish the thought…)?
I can find the cultured stone on the web, but not the installation detail. If anyone can help with a link or your experience, i’d be grateful.
Thanks,
Colleen
Replies
Run the stone up from the roof deck. step flash as usual and counterflash like real stone. Running the flashing under the stone veneer is only gonna make a nightmare for the next roofer.
Cultured stone is much softer than real stone. If you wanted to and the pattern allowed you could cut a groove with a circular saw and a masons blade for the counter flash.
I would use copper or lead coated copper or lead and step flash behind the cultured stone before installing it. Make the roof side of the step flashing long enough that it protrudes past the face of the cultured stone several inches. When a reroof happens, the flashing can be accessed and re-used or the chimney can then be flashed as Maverick suggested in the previous post. The flashing behind the stone will repell any h2o that penetrates the cultured stone. I'm not sure how tight that stuff really is.
sooner or later someone is going to flash the face of the stone. If not this roofer then the next. cultured stone is advertised as being impervious to water. After all it is basically concrete with a small agregate.
I dont think your gonna get the stone to adhere to aluminum or lead flashing. You would need to install metal lathe and a scratch coat of mortar over the step and counter flash.
If you really want to bury the flashings you better install a barrier between the steel lathe and the flashings to prevent galvonic corrosion. Maybe using pieces of Ice & water shield.
I guess i didn't describe the situation clearly. The roof was already re-shingled, and the old AL step flashing for the chimney worked in, all lapped, caulked and nailed together, before the owner told me his new desire. I'm not working from the ply surface at this point and the thought of ripping up the work i've done is painful. I knew i could attach cultured stone to the block with mortar, but was stumped at what to do in the already flashed area--mortar would slide right off, no?
It looks like it might be more work than it's worth at this stage of the game to cut into the new shingles and do a secondary layer of flashing. It was just that i saw a chimney nearby done with cultured stone (new construction), but i could see no flashing at all, just 'rocks' to the shingle surface. (Some of the pics i saw online looked like that, too.) So I wondered what was the best practice for installing it, but from what you guys are saying, it sounds like that was an aberrant one.
Maybe i'll advance the idea of parging the block into looking more attractive. New territory for me...open to suggestions.
I think you were pretty clear the first time. I got the idea anyway.
AL is not a great long term flashing for around masonry. It will corrode long before the masonry dies. I would do one of two things. Mosatly I am right on line with what Greencu said and use a lead step flashing.
But I also see the concern you have for adhesion to metal with the mortar. To deal with that, your prep coat for the stone application is similar to doing a stucco coat. Affix wire lathe to the flanks of the chimney after reflashing with lead. Lay a shingle or strip of the asphalt roll roofing on the existing shingles so your stone work is not fused direcly to the roof.
Then slap on that scratch coat over the wire lathe. Now you are all preped for the stone.
most stone work is like laying bricks - bottom up. Sometimes cultured works easier top down.
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Thanks for the 'reinforcement' on the lath idea. I'm adverse to putting a 'bib' of flashing inches out from the stone, so i think covering the exposed Al with Pb flashing started a bit higher might do the trick. I like the idea of a scratch coat to start with, to give a firm base for mortaring the stone over the flashing. The air gap of only a shingle thickness is certainly acceptable. I suppose in 30 years someone else will tear it all apart, anyway!
OK, i've got a plan...merci!
do it right.
tear off the already re-used flashing ....
get down to a solid substrate ...
and do the job right.
times like this ... there's usually a right way ... and an easy way.
Jeff
Buck Construction, llc Pittsburgh,PA
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