Mom has a stone f/p and chimney on 35 yo house. She’s had problems with leaks recently. People have tried various caulks and flashing improvements and sealers, but leaks still persist. Latest theory is that the mortar is bad. It’s described to me as “spongy” and “apparently they used the wrong mix and water is leaking through it like
sieve, onto the plywood.”
So the question is, how long should mortar last without becoming porous? I once had a brick chimney in bad need of repointing, but that was 80 years old. Does 30 years sound right for needing repointing? Is it possible that repointing is a legitimate answer? Or is there another possible answer for a leaking problem that showed up after 30 years? The guy looking at it says the answer is to rebuild the chimney out of concrete and lose the beautiful stones. Repointing is my thought, but want to check here before suggesting it to Mom.
Replies
Im with you, I wouldnt want to loose the stones, even if I had to rebuild the chimney with the same stones.
If its 30 its most likely lined, so the cap might be bad as well, or the cause, but I would recap and repoint if it seemed structurally sound.
Im not a mason though so Id be interested to hear others comments.
"Plywood is still wet" caught my eye--is it possible that it's bad flashing instead of bad mortar? Or bad mortar on gone bad flashing?
Chimney cap is a good place to look, if only to see if there's flue/liner, etc.
cloud- check flashing again, common leak problem house settles, flashing can pull away, tucks into mortar joints can be bad, etc. if chimney is structurally sound, repoint as needed and recap it apply masonry sealer to exterior stonework and mortar joints to seal out water reseal periodically add s.s. cap
if chimney reduces in width from firebox to straight flue, check the drainage slopes.. they should be capped w single piece of bluestone or granite, not with pieces of stone and mortar joints they should be sloped AWAY from the house(perpendicular to exterior wall), NOT sideways and parallel w exterior wall had a new house this summer w leakage; firebox / flue reduction on both sides of stone f/p drained water sideways and down against brick exterior wall of house, compounded by both slopes built of several pieces of stone with mortar joints the mason changed drainage slope to point away from house, capped ea. side w single piece of bluestone, end of water problem bluestone should overhang chimney on side and bottom to divert water away from masonry bottom edge should be cut plumb w masonry blade for same reason, proper drip edge
if no clay flue liners, or if they're in place but damaged, and mason can't repair them, reline chimney yourself w stainless steel kit, looks like a big slinky use largest size that will fit within flue drops into place from above, trim to length needed s.s. hardware to attach and secure at top expensive if contracted out, but kit is under $200. from a supply house w a f/p, need sheetmetal pan (use s.s.)fabricated to seat @ damper, cut opening to receive s.s. liner seal w proper heat rated cement
Repoint and flashing.
Mortar is always porous from day one. A seal coat will help
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jim.... in our area a "stone chimney " would mean "field stone" as in New England stone walls...
the only way they will NOT leak is if they are thru flashed.... any flashing that is merely let in to the joints will be bypassed..
IE: some place or other there WILL be a leak... it's the nature of the irregular stone..
so the flashing has to be designed to intercept the leaks and redirect it out of the chimney rather than allowing it to follow the chimeny into the structure
googel on "thru flashing" or look it up in a masonry manual, or Arch. Graphic Stds.Mike Smith Rhode Island : Design / Build / Repair / Restore
Like mike said.
I have built upwards of 40 stone chimneys, only 1 I didnt thru flash, also the only 1 I have ever had leak.
tear the top down to the roof, thru flash and rebuild.
Thanks for the comments. In this picture, do y'all think they have the details right, or would you change anything? Any diff with stone vs the brick they show?
View Image
Where the counterflashing is simply raked into the joints at the bottom of the chimney in your graphic, it should be thru-flashing...going all the way to the flue, then returned up a bit.
I'm going to try to link a graphic from a pdf file. If it doesn't work, or if it does and you want the entire article, email me and I'll fire the attachment back to you. I can't send attachments via taunton's email.
Mongo
Edit: Forgot to add, graphic courtesy of JLC Nov '92.
Edited 12/12/2004 12:19 pm ET by Mongo
Thanks, Mongo. My diagram came from the Masonry Advisory Council: http://www.maconline.org/ Interesting that they didn't show the same flashing detail, huh?
I noticed the difference in the diagrams too. Although it's been more than a few years since I've done this for a living, this forum is the first place I've heard of thru-flashing for chimneys. I'm living back in the area I did most of my work, and no one's complained. One thing I did do differently on stone chimneys than others I know, was brick the chimney thru the roof, flash over that, and then start again with the stone.
Seems like a very similar technique, to me. In the first graphic the thru flashing was under the cap, near the top of the chimney, to keep water from sliding down between the flue and the brick. In Mongo's graphic the same thing only lower, closer to the roofline so any water that gets absorbed by all that masonry and whicks back to the flue will again be diverted out instead of passing down into/onto the framing.
Either one seems like a danged good idea to me. Glad I saw it. Never heard of it or even considered it before. Heck, I gues it wouldn't take much to thru-flash both places, just under the cap, and just above the roofline too. Why wouldn't you? We're talking what, an extra hour or something?
Hey Mongo - do they show any cap details in that article?
jb,
Nothing really regarding the cap in that article. They had a different article several years ago about troubleshooting chimney leaks and broken chimneys. I thuoght it was nicely done.
The thing I remember about caps from that article was:
1) Wrap the flues with something to isolate the flue from the poured cap. You don;t want the flue bonding to the cap, as it could lift and crack it. I think the guy in the article used plastic crime scene tape. I usually have the mason use a wrap of foam sill seal. Caulk the gap wth quality sealer.
2) Use something under the cap to isolate it (bond breaker) from the chimney brick or stone. The article advised to use anything...tar paper, etc. I advocate using through through flashing there as well, kind of like the flashing under the cap in cloud's graphic. Just like you wrote, throught fashing up top under the cap, and down at the roofline.
3) After the cap is poured, keep it damp. Wet burlap covered with plastic, whatever...just keep the sun from beating down on the just-poured cap so it doesn't prematurely or unevenly cure/crack and warp or curl. Fibers in the mix strengthen it especially around the stress raisers/flues.
4) The mason doesn't do it, but I've gotten up on the chimney and used a grinder to grind a groove around the perimeter of the cap on the bottom of the overhang, a drip groove, to prevent water that flows down the edge of the cap from wicking back onto the stone or brick that makes up the chimney.
Thanks, man. Dammm I'm glad I read this forum.
Here's a tip that works well when trying to find a leak.
Try and duplicate the leak with a hose on a dry day. In other words use a hose to wet the flashings around the roof - give them a good soak at a low water pressure.
Then try other spots.
The advantage of doing it this way is you can really focus the water in a small area and thereby identify the exact source of the leak.
Be Careful - Make sure you are harnessed up - wet roofs are a death trap.
I perfer to see flashing woven into the shingles as opposed to sitting on top of the shingles, now because its sitting on top of the shingles or atleast it looks that way in the picture there has to be secondary flashing underneath also, if you can see water coming down the chimney from inside the house then this could be part of the problem
can you get some pictures for us it may be just flashed wrong and somebody could be trying to stiff ya
It's 10 hrs away. Sorry. This is the kind of thing where Mom calls and says, "This nice man was over...he's the son of my friend Mabel...you remember Mabel, right...her brother had his gall stones out last summer...well I was telling him about the water leaking and........"Know what I mean?