Water Proofing External Chimney bricks

[Jerry_NJ]

We have a large "used brick" external wall fireplace chimney structure, three flues, two fireplaces and one stove. The structure still looks fine, albeit old (as intended), the mortar is in good condition, but....

We had "our" chimney guy in today to do a roto-cleaning to remove some of the creosote glaze that has accumulated over the years due to the operation of insert that was simply dumping its smoke into the fireplace. We had this service performed to help remove/reduce a chimney/old-fire odor that has developed in recent years. He noted that there was some condensation inside the chimney...this could contribute the odor generation. I asked if there was someway to seal the brick and he said "yes", he has a process/product that is sprayed on the external brick area, including the apron at the top of the multiple chimney stack. He said this spray soaks in and is invisible, but does stop water penetration from the outside, while allowing moisture inside the chimney to evaporate.

Any experience/advice?

Thanks,
Jerry

 

[begreen]

Hard to say without knowing the product. Might be able to accomplish the same with Thompson's Water Seal.

 

[webbie]

There are a number of clear masonry sealers, I think they are silicone based. Keep in mind that neither that nor the roto-cleaning will always take care of any smells. Creosote and smoke have soaked into tons of masonry for years and it does not take much to cause a smell.

 

[Jerry_NJ]

Thanks, I can't say I've ever been happy with Thompson's products when used on wood. I bet I have a near full gallon of it in the basement somewhere.

I have read on the web on the subject of waterproofing brick and have read about concerns in trapping moisture inside the chimney...the following seems to be a solution and fits the description my chimney sweep gave me:
A DEFY Water Repellent for Brick treatment is 100% vapor permeable, which allows the water vapors to escape. This reduces costly chimney repair such as spalling, scaling, deterioration, and freeze-thaw damage that results from trapped moisture when clear coatings and water sealers are used for waterproofing brick.

Looking for a dealer, the nearest is over 60 miles away, none at Home Depot it seems. Looking on the HD web site I see a lot of Thompson's stuff under a search for water proofing". While my reading so far has left me a bit confused, need to study rather than "speed read" some of the references I turned up, it seems on would like to make the brick/mortar shed water from external sources, yet evaporate moisture coming from the inside.

If he comes up with a price bit of several hundred dollars, I'll have to think real hard and may DIY if it seems to be the right answer. If he comes in under $250 I may just give it a try. Seems all that one needs to do is use a low pressure sprayer to apply the DEFY stuff, and while I have a two story house, chimney at least 32' up from the outside ground, it shouldn't require a only reasonable ladder work, and a trip to the roof, something I'm not going to do.

 

[RedRanger]

Jerry: any of the above will work. timing is crucial. if you get 3 or 4 weeks of dry sunny weather this july or august, then go for it. just don`t be silly like I was the first time and try and use a brush :red: did my chimneys 2 years ago,first with a brush, and then I woke up; and bought a sprayer,

You do need the heat and the time eg. lots of sun and heat for at least 3 weeks before you do the work. if you get that then go for it. Sounds simple enough, but you really do have to keep an eye on the humidity,the temps and the forcast to get the timing right. Maybe not so crucial for you,but here in the pacific north west,it really is important >

 

[Jerry_NJ]

Sony... thanks for the input. Can you give me/us any idea on why you did the waterproofing...did it fix something, or was it done as a recommended preventive maintenance procedure?

My chimney is about 25 years old, and it looks like it'll stand for another 50 years (what do I know?)... still we have some efflorescence on the floor of a bedroom fireplace (that has never been used in my 20 years here), and some on the outside (hard to say, this is really used brick and has some white paint splotches...), and the real driver, we have fireplace odor from the fireplace in the living room which has seen regular use via a simple insert. These are the drivers that has caused me to think water proof, and the chimney company guy (son of the owner, who I've hired several times over the years) was happy to sell me a service, which he highly recommends...I expect a proposal in a week or two, so I have no idea what it'll be priced at, and I'm still trying to determine the real benefits from users, not sellers.

The product I've read about recommends application with a "low pressure" sprayer...which I take to be a simple hand pump garden sprayer. All that said, I'm moved more to DIY, I can reach areas over my head/ladder by at least 5' using a sprayer, if the over-spray isn't too hazardous.

We have too much humidity in NJ in the summer, but not a lot of rain in July and August, so that may be a time when the brickwork will be dry. The idea seems to be the proofing must shed water from the atmosphere/outside while breathing interior moisture. Seems like an impossible behavior, but the product says that's what it does, same story from the chimney service.

 

[hilly]

Jerry,
I did this three years ago on my chimney. The water was being absorbed by the bricks and then pieces of brick would split off in freeze/thaw cycles. Research very carefully for a waterproofing product.

From my reading a few years ago, Thompsons was definitely not the right product for this. If I recall correctly, Thompsons coats the surface, whereas the product you want will penetrate the brick and set up a water barrier there. I think I had to do two coats within fifteen minutes of each other, or the first would set up the barrier and the second would not penetrate, and like the product you're thinking of, the stuff I used went on with a sprayer as well. It was very viscous, almost water-like, and cost upwards of $60/gallon.

I had to go to a specialty concrete place because no local stores had it.

 

[begreen]

Perhaps it would be good to have a mason look at this chimney? It may be there is a leak and not condensation? Condensation is formed by interior warm moist air meeting the cold brick surface. I don't see how an exterior sealer is going to make a difference. However, if the moisture is due to a mortar, then it might. But it may need replacement of a cracked brick or bad mortar as well.

The other thing to check is if there is a way for interior air to be constantly drawn into the chimney. Suspects would be an open or leaky cleanout door or a poorly sealed additional tap into the flue. When I took out our chimney I found two old taps that were buried in the wall. I remember one place where a bathroom fan was being dumped into an older (at the time unused) chimney.

If it turns out to be a leak check with your mason for the best remedy. If it is a sealer consult the local masonry suppliers or mason to see what they like best. I suggested Thompsons because it's easy to find, but am not advocating it as the best product out there.

 

[Jerry_NJ]

Thanks, I talked with a neighbor today who also has a used brick fireplace, his being about 5 years older than mine. He has had his sealed with "Chimney Saver" and also needed a lot of brick mortar repair, spending over $2,000 before he was done. He had water coming into the fireplace, and when water proofing didn't completely solve the problem he had major masonry work done...says no more water to date.

The more I pay for a fireplace, the less economical it looks for a heating solution. True that even if I purchase cut/split/delivered hardwood firewood, the cost of heat is less than Oil at today's prices. It isn't less though than my electric geothermal heat pump. Guess I need to add to my cost of electricity about $350-$400 per year depreciation on the heat pump which is similar to the cost chimney maintenance costs.....just no free rides/lunch.

 

[begreen]

Do you have the same issue or just some observed condensation? If it truly is condensation, then it seems a block off plate could stop this issue completely.

 

[Jerry_NJ]

I have not seen the "condensation", I think it is visible only from the roof, looking down the chimney. I don't go up there, roof too steep and high, the attic was build for the addition of a third floor via adding some dormers.

Looking of the web haven't found a lot in favor of water proofing brick, in fact this: http://www.oldlouisville.com/circa1900/brick-structures.htm is a strong argument against using waterproofing on brick...or I misunderstand the point of the "brick-structures" article/treatise.

 

[RedRanger]

Okay,found the stuff I used before. It`s called homecrete,it is a acrylic clear sealer that goes on white and then changes to clear.Can`t remember if I bought it at homehardware or homedeopt? 'Anyway the ingredients are-diethylene glycol,monobutlyl ether,and 2-butoxyethanol.

You are supposed to clean the bricks first with tsp. Then you will have to wait 48 hours for the surface to be completly dry before applying. Hope this clears things up for you. good luck.

 

[Jerry_NJ]

sonnyinbc,

Thanks, I'll look Homecrete up on the web and see if I can find were it is sold in NJ, if it is sold in NJ.

My chimney guy did mention power washing before applying whatever he has.

I really have two steps to a decision that have not been fully worked out in my mind yet.
1) Is water proofing a good thing, good for the brick chimney?
2) What does it cost to have someone else do it.

I'm waiting for an offer from my chimney guy, and I have the name of the chimney service that did the neighbor's chimney, for $175 I think. Given the amount of work that needs to be done well above ground I'll go for a hired job if I can conclude the answer to #1 above is yes. You seem to have seen some benefit.

 

[billb3]

I don't quite understand the advantage of sealing a vertical wall of bricks, either.
If anything, I'd be worried about trapping moisture in them .

 

[Jerry_NJ]

Still doing research, here's another reference that supports and explains why waterproofing is right/good (then too they are selling): http://www.home-pro.com/homebook/articles/ChimneysSufferTheHeartbreakOfPsoriasis.htm

So, what's the right advice? I have also read an interesting thread on the Garden Web Home Repair Forum, there someone did major repair and waterproofing, like my neighbor has. I sent them an email asking how it has worked out...the thread was a couple of years old.

 

[thechimneysweep]

Brick is porous, and will absorb moisture if left unprotected. If the chimney is unlined, moisture condensation as a result of combustion will soak into the bricks and mortar joints from the inside. This is one reason code requires a suitable liner for all brick chimneys.

An unprotected brick chimney exterior will soak up rainwater. Given time and enough dry weather, this moisture will vaporize and evaporate away (even condensation from the inside of the chimney will migrate to the outside and evaporate eventually). Problems occur when moisture is trapped in the brick, or when exposure is so constant that the brick structure doesn't get a chance to dry out.

A soaked brick chimney can cause several problems, including:

Efflorescence: if the chimney remains soaked for too long, the lime will eventually leech out of the mortar joints, causing unsightly white stains, which are particularly annoying when they "bloom" on the inside walls.

Mold/mildew growth.

Breakdown of the binder which solidifies the mortar joints (this action is accelerated by caustic agents in the exhaust). We've seen chimneys where the mortar has been turned to mush.

Spalling: if the soaked-in water should freeze, ice expansion can break away the outer surface of the bricks to the depth of water penetration.

You don't want to seal the outside of a chimney with any kind of impermeable chemical, or the soaked-in moisture will be trapped in the bricks, worsening the above problems.

The best masonry chimney sealants are electrostatic. For some reason, water always carries a negative charge, and so do electrostatic sealants. Like charges repel, so water that comes into contact with an electrostatically treated chimney won't soak in: it just runs off. Meanwhile, according to the manufacturers, water VAPOR evaporating through the bricks from the inside passes right through the sealant. As a bonus, electrostatic sealants soak deep into the brick, and only need reapplication every 10 years or so. We have used an electrostatic product called Chimney Saver for about 20 years now, and it works.

 

[Jerry_NJ]

tcs,

Thanks for your detailed/expert input. I had found "Chimney Saver" as one product in my research on the web. I don't recall it saying anything about being "electrostatic", but I like the idea (I'm a Electrical Engineer/retired) :>) I do comment, however, I don't see how the electrostatic shield can differentiate between water trying to migrate into the brick from the outside, verses water trying to migrate out of the brick from the inside.....but I do know my chimney service guy did say the service he offers has that critical characteristic, no water in, but water works out. I think he said something like 10 years too. I'll ask what product he plans to use when he gives me a price. He also commented that he'd apply at the crown/cap (top cement that joins the three tile flues and closes off the top) and that it would seal any fine crack on that too. I had my roofer patch that area up about a year ago when he was here checking flashing and shingles.

 

[thechimneysweep]

Hey Jerry,

I'm not sure about the physics either, but witnessed the following demo at a Sweep Convention a couple decades ago:

Two brick "bowls" were constructed, side-by-side. One was treated with an electrostatic sealant on the INSIDE. The other was treated on the OUTSIDE.

Both were filled to the top with water, and clear plastic panels were siliconed in place over the tops.

I'm not sure how far in advance of the convention this demonstration was set up, but by the time I saw it, the water level in the outside-treated brick structure had lowered, while the level in the inside-treated brick structure was still right near the top.

There's more: we started using that product, and soon thereafter one of our Sweeps spilled some on the sidewalk outside our store. For about a decade thereafter, you could clearly see that light-gray splashmark, surrounded by dark gray rain-soaked sidewalk, every time it rained.

 

[Jerry_NJ]

Thanks Tom,

I trust my chimney service, a father and son team, plus a couple of long term hired hands, still it is what he sells, and he may (want to) believe it is great. I will ask him what product he uses. Some of my caution comes from some negatives I've read. Still, my 25 year old chimney sill looks good, so it is worth preserving, and it may well be "pay me now, or pay me later, and a lot more if later".

Hi to Bellingham, I lived in Seattle for a number of years, served a tour a the Sand Point Naval Air Station, and married my wife in the base chapel, then I got out of the Navy and earned a degree in EE at the University of Washington. Sadly I moved upon graduation and have never returned to the NW. I think the property values are up so high there we couldn't afford to return if we wanted too...but we don't miss the rain.

 

[dvellone]

Having repaired, repointed and rebuilt many chimneys over the years I can assure you that waterproofing bricks is unnecessary. Most folks and some of today's generation of brick masons are unaware of the grading of bricks according to weathering as well as extreme locations. (freeze/thaw cycles) Bricks should be chosen for application, then aesthetics. Unlike a concrete block which is never intended for an exposed chimney surface because of it's ability to absorb a large amount of water, bricks have a much harder "skin" that impedes water absorption to the point where it doesn't adversely affect the integrity of the brick. Of course, this is where the weather grading comes in to play in the case of an exposed chimney in a zone 3 climate - some bricks have a harder and "glazed" surface to protect even further. There are many products out there that claim that they can provide the protection you need, though in my experience as a mason they are unnecessary. Are your bricks spalling? If they are, it is much more likely that water in a larger volume is entering from above. Check your cap. Is it cracked? Is there a unprotected gap between the flue tile and the cap? If you have efflorescence the same above applies - excess water entering from above that cannot easily exit the bricks because of their density(which in turn prevents excess water from entering the vertical surface!) What do the mortar joints look like? are they sound - hard and solid? Rotten joints that are crumbling provide an entrance to driving rain or water running down the surface, and will allow a large volume of water to enter. If you don't have any spalling or efflorescence and your chimney is in good shape, protecting the surface of the brick is redundant and a waste of time and money. In a masonry chimney the flue tile is free from the outer units. In other words, they are stacked upon one another, often mortared together with a bit of refractory clay. There is airspace between them and the bricks top to bottom. Many fly-by-night "masons" would mortar everything together creating fatal and and largely unrepairable future problems. This could be the source of your condensation though it would seem unlikely if your chimney and flue tiles have no rupturing going on. If your tiles were set correctly you would do well to remove a couple bricks from the top of the chimney on the north or east side (away from prevailing winds) as well as from the bottom of the chimney and replace them with brick vents which will allow air circulation. If you have no airspace you can certainly install weeps to encourage the mystery water to escape. If the condensation is, as I understand, on the inside of your flue tiles it's not coming from the outer surface of the bricks. I didn't read all your posts in great detail but, you might consider that the moisture is from within you house. If you have a fairly tight construction with vapor barrier, warm moist air is escaping via your chimney draft and condensing on the cool walls of your flue. If its just a little bit of condensation and all seems well with your chimney I wouldn't worry about the bricks or much else.

 

[dvellone]

Sorry, but one more thing I just caught on one of your posts. Do not apply the cement to the top flue tiles connecting them to the cap. This is a very necessary expansion joint that will soon rupture when you run your stove. You can seal it with a high temp caulk which will allow for expansion and contraction between the different density of materials and the heat of your flue. It will seal out water.

 

[Jerry_NJ]

dveellone,

Thanks for taking the time to give expert advice. Around here, central NJ, it seems all the chimney "guys" see waterproofing as another line-of-business to make some (fast?) money. I have talked with only two, but both are sellers of waterproofing.

I had the cap repaired based on advice from my chimney sweep service. As I was having a roof inspection anyway I asked the roofer about patching the chimney cap, he said he could do that, and did. I don't go up there, two stories and steep slope on the roof, so I don't know how the interface between the chimney tiles and cap was handled. Later, about 6 months later, my chimney sweep was up there again and as I asked him to check the work, he told me the job look good...but there were some small cracks that could be filled by the waterproofing when (if) he waterproofed the overall brick.

Again, my chimney looks good on the outside where I can see it, but there is some efflorescence on the outside brick and in an upstairs fireplace floor. This could have been due to the old cracks in the cap, not sure. Also, the brick is used brick, has some splotches of paint and the like on it. All bricks and mortar looks good, but the bricks are somewhat soft on the surface, i.e., not the hard glazed look of modern brick used to build houses today. The subject chimney has a LockTop damper on top, which I have left open the last couple of days to let air flow... reasonable temperatures outdoors these days and low humidity.

I'll hold off on the waterproofing. and will be sure to have the cap repaired by a specialist when (if) I get around to having a new insert installed in one of the fireplaces.

 

[dvellone]

Jerry, the "softness" of the bricks believe it or not, isn't always indicative of the weather grading. I have done historic work using bricks that seemed soft and were in fact graded "sw" indicating severe weather. Years ago the average building brick was seemingly "soft" on the outside, though cores were solid. The clay of all bricks is dense and the outer surface receives the longest and hottest firing, always giving it a weathering ability. All bricks in general are made for outdoor use, and unless spalling causes the outer surface to fall away causing the softer core to be exposed, will withstand the weather well. Efflorescence itself isn't particularly damaging to your structure but is a symptom of water trapped behind the mortar joints which then can freeze rupturing the masonry structure. Your damper, if I understand correctly, is located at the top of your chimney? I might take a look at that situation as the possible culprit to the water causing the efflorescence as well as the cracks in the cap. Efflorescence generally does not occur from moisture entering from the outside of the units. It occurs when water enters at a greater rate than driving rain to the face of the bricks can cause - usually from above or from behind when water is trapped and held against the brick with no place else to go. It is unlikely for that amount of water to enter the face of your chimney. Consider the historic brick buildings of multiple stories that are battered by driving rains and are absent of efflorescence. Your sweep or mason contractor should be able very easily find where the water is entering. As I mentioned above, I'd check the damper and especially where the steel of the damper connects to the masonry. Also of consideration is where the chimney exits the roof or meets the roof if it is entirely outside. Check out the flashing in particular or the rake end if applicable for water entry. Follow the trail of efflorescence.

 

[Jerry_NJ]

Dvellone,
Thanks, maybe my best action is to have, I'll not work that high, the chimney cap resurfaced/sealed, and leave the brick alone. It looks fine to my eye, the Efflorescence is not particularly ugly, may go unnoticed until one examines the chimney. I'm negotiation to have a new insert installed, and of course that's a new stainless steel liner and new cap for that liner, so the chimney expert is up there anyway, should be a reasonable additional amount to have the cap/apron resealed, as I think I said in this thread, my roofer was here last fall and while inspecting my roof put a coat of something cement-link on the cap/apron to fill some 1/4" cracks the chimney sweep reported on the last cleaning.