Chimney leaks water?

[MarkV]

Hi all. I have a brick chimney that services a wood burning insert and has a single tile flue with a cap running in it. The cap only covers the flue leaving around 1 1/2' of chimney top on either side of it exposed. Those areas are covered with mortar and have a good drain slope to them. The problem is that the mortared areas have developed cracks that are letting rain into the chimney cavity. Now in heavy rain we are getting some water leaching through the brick face. Not into the firebox but through the brick facade both inside and out.

Any suggestions on how to reseal the mortar areas? The cracks are not huge, 1/4" wide or less, and I think silicon would seal them. I am concerned silicon would not hold up to the stove heat and sun exposer though. Are there any products out there for these types of applications?

Thanks,
MarkV

 

[JB4310]

Do you have a cathedral ceiling, no attic space above the room where the stove/firebox is, brickwork exposed all the way up?
The reason I ask is all chimneys transfer some water through to the inside through gravity and capillary action, (masonry is absorbent) if you look at almost any chimney in an attic you will see water stains on the chimney as well as surrounding framing. With a cathedral ceiling there is no buffer and any amount of seepage will show up in the finished space.

As far as the 1/4 inch cracks go, a good high quality silicone is best, they are to small to fill with mortar, cut the tip as small as you can and just inject into the crack, strike it clean with your finger, don't smear it on the brick, the stuff is glossy and will contrast with the masonry work.
Look for any other smaller cracks, even hairline ones and seal. after all holes and cracks are sealed apply a high quality spray on water repellent, we use Siloxane, usually only need it from the roof line up, it's clear when dried so wont change the appearance at all.

There should be no heat from your stove affecting the exterior of the chimney, Don't worry about UV factor.

Use GE exterior window and door silicone, that's about the best, don't use that stuff that comes out white and is supposed to dry clear, the GE comes out crystal clear.

Good luck, JB.

 

[MarkV]

It is a cathedral ceiling but the chimney is not on the gable end. I should have mention that is an exterior chimney with 8' exposed to the interior of the house.

JB I may not have been clear as to where the cracking has occurred. This is on the top of the chimney where the flue exits, where Santa comes in. There is no exposed brick in that area, just the mortar they top coated with. For sure this is not capillary action, way too much water.

I really don't know how hot it gets up there during wood burning season. The clay flue tile and the air space around it may make heat a moot point. I've just never climb up there in the winter with the wood stove going.

Thanks for the input,

MarkV

 

[JB4310]

I understood you about the cracks in the crown, but you should also look closely at the rest of the chimney from the roof up, If your chimney is over-sized as an architectural element and you have brickwork all the way to the ceiling inside, you'd be surprised how much water can come through the brick, especially some of the newer types of brick. Usually water that comes down the flue or around the flue will show up in the firebox not on the veneer, typically water that shows up on the veneer is coming through the brick work above the roof.

Don't forget the crown/top of the chimney like the peak of the roof gets the least amount of water, the sides get much more. Look at a typical masonry chimney with an uncapped 12x12 flue pipe for the fireplace, you can look up from the fireplace and see blue sky but yet there's never a drop of water in the fireplace, even in pouring rain. Haven't figured that one out myself yet and I've been repairing chimneys for 30 years. of course some fireplaces do leak and require a cap but the majority never do.

Definitely seal up all holes and cracks that are obvious but look closely for the tiny hairline cracks as well. check the top of the counter/cover flashing where it's cut into the brick joint, look closely at the entire flashing area being at the bottom of the roof like that. Is there a cricket or a saddle behind the chimney? You probably will need to apply water repellent as well.

It shouldn't get hot enough up there to interfere with any material you apply.

The reason the cathedral room came to mind right away is because like I mentioned it is a common problem in single storey construction where there is no buffer area above the finished room.

Do you have any pictures of the layout?

JB.

 

[MarkV]

Thanks JB, I'll take a closer look at all you have mentioned. I never have learned to post photos. Maybe it is time.

MarkV

 

[Egon]

good high quality silicone is best,

You can get a high temperature silicone. The ones I've seen are red and were used for gaskets on the dog house doors on larger engines.

On our house we have a double clay flue brick chimney. One flue has the furnace. The other flue has a stainless steel insert for the fireplace insert. The chimney top has a stainless steel cap that covers the entire top of the chimney. This cap has in turn two other round stainless steel flue covers with their own cap. This pretty well seals off the top of the chimney.

If the leak in your chimney is from the top the silicone would be the easiest solution.

You could also consider forming up some corrosion resistant metal covering [metal cap] that will extend down and around the top sides of the chimney.

Another approach may involve laying on layer of metal mesh reinforced mortar but this method may be subjecting to cracking as the original has done.

The attached picture of our chimney.

 

[EMS503]

Get hold of a chimmeny sweep and ask them about this new sealer they have, I forgot the name off the stuff but my chimmeny had cracks like yours and they coated the top of my chimmeny and no more leaks. It was a little pricey but it beats the water damage. I will check to see if I have the name and let you know.

 

[sal64]

i had similer prob i have a stone chimmney i sealled crackes with sillicone calk and used tomsons water sealler, about 10 coats,never had a prob again.

 

[cowboy357]

Dont Quite understand why You Would use silicone , when Theres specific products used for this purpose .

Quickcrete commercial grade Mortar repair is the best I,ve found. Also comes in a Caulking tube , Found at most stores Like Home depot, Lowes & such .

Easy & Safe to Use , as its an Acrylic , Dries Quick & Waterproof . It Also has an Adhesive Quality for using to Place the Frontal stone for inside & outside uses . I Think its about 8 Bucks , But is a One time Fix IMO & Doesn,t just seal the Cracks But Strengthins them & You Barelly tell the Cracks Were even there as It Matches allmost Perfectlly .

The Other Option is Having a Custom made Stainless steel cap Made for the top cap wich hangs about 2 inches over the side Also bullet proof but More Expensive . just My Opinion , I Had the Same Problem a couple of Years ago . Bob

 

[cowboy357]

Dont Quite understand why You Would use silicone , when Theres specific products used for this purpose .

Quickcrete commercial grade Mortar repair is the best I,ve found. Also comes in a Caulking tube , Easy & Safe to Use as its an Acrylic , Dries Quick & Waterproof . It Also has an Adhesive Quality for using to Place the Frontal stone for inside & outside uses . I Think its about 8 Bucks , But is a One time Fix IMO & Doesn,t just seal the Cracks But Strengthins them & You Barelly tell the Cracks Were even there as It Matches allmost Perfectlly .

The Other Option is Having a Custom made Stainless steel cap Made for the top cap wich hangs about 2 inches over the side Also bullet proof but More Expensive . just My Opinion , I Had the Same Problem a couple of Years ago . Bob