I’m wondering if it’s ok the seal exterior brick on a central chimney. I did a remodel where the chimney cobbled over the stairwell. I attached cement backerboard on the inside and plastered it to be the interior finished surface. I neglected to put plastic as a barrier between the brick and the backerboard and now, when we get a serious rain, the brick becomes saturated and wets the upper section of wall. Can I seal the exterior brick without risking freeze/thaw damage to the brick? The chimney is on Cape Cod.
Thanks
Replies
I can't remember brand names because it was so long ago, but a mason friend said there is a sealer that keeps liquid water out of the masonry but lets moisture vapor escape. Try a good mason supply house, or perhaps the internet.
Don't seal it with something that won't let vapor escape.
You could not have put plastic on the brick anyway because code requires a 2" space between the chimney and anything flammable. The plastic would have deteriorated quickly.
Have you checked the chimney cap? Often a great deal of water comes through cracks in the cap, either around the flue or in other cracks. And you should have rain caps with screens on top of the flues, too.
Thanks for replying. The chimney is brand new and the mason warned me not to seal the brick to prevent freeze/thaw problems. Maybe I'll Google it!
hello 35 yr gc here,I've been the route.. wait till its dry, then seal the whole thing. MAKE SURE the cap is properly done before sealing. any effloresense on the chimney will become permanent when it's sealed in. If the brick is sealed properly, water can't penetrate, making the freeze thaw issue moot. the key phrase here being "properly sealed" ,do it twice, this is one place where I do it myself. I use "Water Sealant" Made by PK Professional products of kansas. call them at 1-800-676 7346 to get a local dist. use a cheap pump sprayer, almost impossible to save one after using this stuff. where it warns you to mask off areas, pay attention! think rain-x on steroids. no known way to remove it from glass. built a house for the guy in charge of PPGs aircraft glass division, he said they were the worlds larget user of this molecule. ever seen rain drops outside the plane window? remember, a chain is only as strong as it's weakest link, seldom will you see that proven more than in homebuilding. jim
Your mason is correct.DO NOT seal the chimney. That will create greater future problems.
a. If it is a brand new chimney I doubt the water is coming from the brick.
b. If it is a brand new chimney I doubt the water is coming from the mortar joints.
c. If it is a brand new chimney I doubt the water is coming from the cap.
d. It takes a long time for water to migrate through brick and then get soaked up by nearby plaster or gypsum board. Take a brick, soak it in a bucket of water over night, so you know it is saturated. Lift it out of the water and lightly pat dry. Now hold it up. Do you see any more water dripping from it. No. But it is saturated with water! It doesn't want to let the water go. That's brick.
My guess is that the chimney was not flashed properly of some othere nearby valley in your roof was not flashed properly. The water from this leak may be running down the surface of the chimney.
Let us know what you find out.
Frankie
There he goes—one of God's own prototypes—a high powered mutant of some kind never even considered for mass production. Too weird to live and too rare to die.
—Hunter S. Thompson
from Fear And Loathing In Las Vegas
not to denigrate your post,but I nearly broke a roofer one time because it leaked. finally, after staying on the roof all the way thru the third re-flash with him[yes it still leaked] I called my brick people. they told me the brick met the absorption standard for brick. I was not satisfied, took a random sample of bricks to a local co. that does U.L. testing. sat down and talked with the guys there and you could see the gleam in their eye's. the chance to learn something new. they ran absorption tests, perm rate, and a bunch of other tests I but dimly understand. result was- brick absorption in any batch can vary widely, all the way from impervious to kitchen sponge. as long as the "average" fits in the acceptable range, the brick pass the standard. My brick rep. was most helpfull but pretty much clueless when it came to a fix. Okay, here I sit, Flashing is done right,brick fit in the standards, still leaks. great to know everything is hunky-dory but the damned thing still leaks. seal it. I've had way more problem w/freeze-thaw on un-sealed brick than sealed. the key is to do a good job sealing it. if you miss a spot then water gets in ,can't get out. this is one place you don't send the labor crew or the mason or anybody else to do the job, done right, problem solved,done wrong, total system failure. good luck
Thanks for sharing your experience.It sounds like I have a similar issue.3-4 year old house (and chimney) and I am the 2nd owner.After 3 days of heavy rain, I get water in the fireplace - enough to soak through to the basement, saturate ceiling tiles and create a big mess. I've created a good system to catch the water to prevent additional damage.When I look up the chimney in these conditions - it looks like the flue is wet almost all the way to the top. It is hard to get a good look with dirty water dripping in my eyes.I can get hurricane type rain for 24 hours and not see a leak.I put a cap on the chimney and closed off the 2nd unused flue to no avail.My neighbor's house was built by same builder and my guess the same mason w/ same chimney design. He has no problems but it looks like it might be different brick.I've checked the flashing and it looks like it was done right - if there was an issue here, I would guess that the 24 hour hurricane rain would expose it and I would think I would have water inside the house, not coming down the inside of the flue.I was originally going to "outsource" this job to someone more comfortable with heights but I certainly can relate to making sure the job is done right by doing it myself - especially the cleaning prior to the application of the sealer.I'll post my results (probably in the Spring).
I put a cap on the chimney and closed off the 2nd unused flue to no avail.
Did you put a cap on the chimney or just on the flue liner? In my experience, the most common source of chimney leaks is the flashing. The second most common source of leaks is the masonry cap or wash. These are usually done very poorly, using the same mortar that's used to lay the brick. They are typically feathered to a fine edge around the perimeter of the chimney, which soon breaks.
The third most common source is poorly filled/compacted mortar joints on the vertical walls of the chimney. Get up on the roof and carefully examine the joints, particularly the (vertical) head joints, to see if there are any gaps or cracks.
Modern bricks, which are manufactured with much greater quality control than the bricks of 75 years ago, are usually not the problem. The poster who recommended sealing the chimney probably met with success because the sealant sealed both the cap and the mortar joints. If you go this route, make sure you seal the cap. If you seal up the face of the bricks and the cap continues to leak, you'll create more problems than you already have.
You can troubleshoot the problem by draping a tarp over the chimney and leaving it short of the flashing. Use a rope to secure it. You need to leave it there for several weeks, which might not be practical at this time of year. If the chimney stops leaking with the tarp in place, the problem is probably the masonry cap.
Thanks - that's an excellent suggestion on using the tarp to help pinpoint the problem. I haven't sealed the chimney yet and won't until the spring but could probably get a tarp up over the top. I only capped the flue for the fireplace and closed off the unused flue.
Sorry to get back to you over a year later, but I sealed the chimeny with a breathable sealer and the problem is solved. Thanks for your reply.
Mike
Sealing brick
What brand breathable sealer did you use?
The sealant is generically called silane or siloxane, and it comes in different brands. It's been on my chimney's exterior for ten years now, and I've had no spalling. I can tell that it works, because the dufus who applied it sprayed a quantity on the adjacent sidewalk, and now that area never stays wet. It also adheres to glass, so spraying may also involve masking. See http://www.brickinfo.org/ for more about maintaining exterior masonry. Be sure to clean the masonry very well, including any efflorescence, as it'll be sealed in afterward.
Thanks for your reply. I sealed it last summer with stuff I found online. I forget the brand name, but so far, so good!
Mike
Tear it down and do it right, at least you'll be able to sleep at night.
saeling brick
Really? What help is it to say that you sealed your brick and can't remember the name of what you used?
Sealers
As one poster noted,the high quality products are siloxane or some variation on it. Prosoco and Sonneborn (BASF now) are few reputable manufactures. It does seem unlikely in is coming through the brick particularly with newer brick that tends to be fired and more dense then older brick. That said, sealing it should have little or no effect on freeze/thaw issues.
You said you used cement backerboard, which can wick moisture like a mother so if is touching the brick, it might be drawing moisture from the brick like sponge and even after it rains the moisture "drive" is wanting to get in the house so it may never really dry out and a heavy rain just pushes it past 100% saturation.