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Discussion Starter · #1 ·
Specifically, for a chimney crown/cap that's crumbling. :confused:

Also learned that brick houses could be sealed like this as well- rather than grout falling apart, silicone prevents that. Sounds a bit extreme to me, but what the hell do I know.
 

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Extremely bad idea to seal brick house with silicone.
Unless you leave drain holes at the bottom of the brick wall.
Moisture builds up behind the brick. Freeze/thaw cycles destroy the wall.
 

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Discussion Starter · #3 ·
The silicone supposedly fills up the gaps better than the mortar. Is it okay for the top part of a chimney?
 

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Boobies!
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I'm with Cinelli--I would not use silicone, but find a good 'brickie' ie mason... The crowns made of mortar will last 30-40 years properly done, and repointing will be better because the patch can 'breathe' the same as the rest of the wall.

I've used silicone patch for block/sidewalk patches where you actually want to keep water out...ie, you are patching a leak...
 

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Discussion Starter · #5 ·
I've used silicone patch for block/sidewalk patches where you actually want to keep water out...ie, you are patching a leak...

But chimneys can leak also. Just the top part, not the entire thing.
 

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Siloxane, a common mason sealant, is a good product for maintaining masonry walls.

It is liquid, and won't fill things like big cracks, weep holes, missing stones, etc .

It probably isn't the best solution for your chimney cap.

I will look for a couple pictures to send you to get your repair in the right direction.
 

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Architectural Graphic Standard, 8th ed.
Text White Line Plan Font

Audel's Guide for Masons, 1924
Text Publication White Paper Paper product


F. D. K. Ching, Building Construction Illus.
Text Line Paper Paper product Font


Note all three examples have a slope, known as a wash.

This is one of the keys to leaking chimney tops.

Siloxane or other liquid applied products won't make up for the lack of this water shedding feature.
 

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as well as....once you have siliconed it and it failed, you cannot re-point it, the silicone will prevent the mortar from bonding, you will most likely have to replace the bricks too!

edit: If the brick is in poor condition, you may be able to buy some time by parging the entire chimney or top at least. Pictures would help us out here.
 

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I'm not sure how old OP's house is.

On older houses where the chimney was originally built without a liner, then when the combustion products meet the cold part of the chimney above the roof, there is condensation, that works it's way through from the inside and eventually destroys the brick.

If the chimney was run for years without a liner, then an up close inspection of the top is needed with replacement if necessary. I know. I've been there.
 

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Discussion Starter · #11 ·
"Parging?" So much to learn........

Here's what we did: The neighbors had their roof worked on the other day. John asked them to do our gutters; they looked and said that the gutters were fine, but they noticed our chimney needed work (which we know; haven't gotten around to finding a mason.)

They offered to patch it up with silicone for $600; John said fine. I figured why not, it'll buy us some time even if it's not the way to go.

once you have siliconed it and it failed, you cannot re-point it, the silicone will prevent the mortar from bonding, you will most likely have to replace the bricks too!

Fuuuuuck......... :mad2: <----(that's the chinmney)

Oh well, such is noob home ownership. :rolleyes: The house was built in 1949; not sure if the chimney has a liner.
 

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"Parging?" ...

... :mad2: <----(that's the chinmney)...
Parging is the application of a thin (less than one inch) layer of mortar to masonry such as brick or block.

The silicone situation might not be a total tragedy, it probably can be abraded (grinder or something) enough that the repair can take place.

Or you could do like I did and buy a different house.
 

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Parging is the application of a thin (less than one inch) layer of mortar to masonry such as brick or block.

The silicone situation might not be a total tragedy, it probably can be abraded (grinder or something) enough that the repair can take place.

Or you could do like I did and buy a different house.
Probably, being the key word here...the job just got a whole lot more difficult and expensive
 

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Discussion Starter · #14 ·
Parging is repointing then?

Guess we should know better than to get a roofer to do a mason's job. At least it's posted here for others to learn from.
 

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Parging is repointing then?

Guess we should know better than to get a roofer to do a mason's job. At least it's posted here for others to learn from.
No, parging is "back plastering" skim coat of mortar on the entire surface
 

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No, parging is "back plastering" skim coat of mortar on the entire surface
If you look at the pictures 10ae1203 posted, the one on the bottom right (1st pic) and bottom of second pic shows a nice pyramidal shape from outside of brick course to center where flue sticks out of chimney. It is parging--ie mortar buildup on a nice angle so that rainwater/snow etc will run off the chimney to the outside. This mortar cap is what fails.

Left unfixed, water starts to work its way down into the brick courses from the top, and can cause failing--but usually it cracks a little first, and takes a good long while before it fails completely.

Mine need doing--but I am not panicking yet....
 
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