Results 1 to 18 of 18
  1. #1
    RoadBikeReview Member
    Reputation: Christine's Avatar
    Join Date
    Jul 2005
    Posts
    15,009

    silicone sealing vs repointing

    Specifically, for a chimney crown/cap that's crumbling.

    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.

  2. #2
    RoadBikeReview Member
    Reputation:
    Join Date
    Dec 2010
    Posts
    5,358
    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.

  3. #3
    RoadBikeReview Member
    Reputation: Christine's Avatar
    Join Date
    Jul 2005
    Posts
    15,009
    The silicone supposedly fills up the gaps better than the mortar. Is it okay for the top part of a chimney?

  4. #4
    We have met the enemy...
    Reputation: paredown's Avatar
    Join Date
    Oct 2006
    Posts
    7,847
    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...
    "There are two novels that can change a bookish fourteen-year old’s life: The Lord of the Rings and Atlas Shrugged. One is a childish fantasy that often engenders a lifelong obsession with its unbelievable heroes, leading to an emotionally stunted, socially crippled adulthood, unable to deal with the real world. The other, of course, involves orcs."
    John Rogers

  5. #5
    RoadBikeReview Member
    Reputation: Christine's Avatar
    Join Date
    Jul 2005
    Posts
    15,009
    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.

  6. #6
    half-fast
    Reputation: 10ae1203's Avatar
    Join Date
    Jan 2007
    Posts
    7,137
    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.

  7. #7
    half-fast
    Reputation: 10ae1203's Avatar
    Join Date
    Jan 2007
    Posts
    7,137
    Architectural Graphic Standard, 8th ed.
    silicone sealing vs repointing-graphic.jpg

    Audel's Guide for Masons, 1924
    silicone sealing vs repointing-audel.jpg


    F. D. K. Ching, Building Construction Illus.
    silicone sealing vs repointing-f.-ching.jpg


    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.

  8. #8
    RoadBikeReview Member
    Reputation:
    Join Date
    Oct 2013
    Posts
    2,105
    I would talk to more than one contractor and get their opinion before taking any action.
    BANNED

  9. #9
    Frog Whisperer
    Reputation: Touch0Gray's Avatar
    Join Date
    May 2003
    Posts
    38,931
    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.
    Of course I'm sure...that doesn't mean I'm right.....

    "There's no sense being stupid unless you show it."

    "that was like trying to teach a goldfish how to play basketball over the phone."

  10. #10
    RoadBikeReview Member
    Reputation: bikerjulio's Avatar
    Join Date
    Jan 2010
    Posts
    7,303
    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.
    We just don’t realize the most significant moments of our lives when they’re happening
    Back then I thought “well there'll be other days”
    I didn’t realize that was the only day
    https://www.youtube.com/watch?v=Y9yrupye7B0

    There's sometimes a buggy.
    How many drivers does a buggy have?
    One.
    So let's just say I'm drivin' this buggy...
    and if you fix your attitude you can ride along with me.
    http://www.youtube.com/watch?v=GekiIMh4ZkM

  11. #11
    RoadBikeReview Member
    Reputation: Christine's Avatar
    Join Date
    Jul 2005
    Posts
    15,009
    "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......... <----(that's the chinmney)

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

  12. #12
    half-fast
    Reputation: 10ae1203's Avatar
    Join Date
    Jan 2007
    Posts
    7,137
    Quote Originally Posted by Christine View Post
    "Parging?" ...

    ... <----(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.

  13. #13
    Frog Whisperer
    Reputation: Touch0Gray's Avatar
    Join Date
    May 2003
    Posts
    38,931
    Quote Originally Posted by 10ae1203 View Post
    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
    Of course I'm sure...that doesn't mean I'm right.....

    "There's no sense being stupid unless you show it."

    "that was like trying to teach a goldfish how to play basketball over the phone."

  14. #14
    RoadBikeReview Member
    Reputation: Christine's Avatar
    Join Date
    Jul 2005
    Posts
    15,009
    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.

  15. #15
    Frog Whisperer
    Reputation: Touch0Gray's Avatar
    Join Date
    May 2003
    Posts
    38,931
    Quote Originally Posted by Christine View Post
    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
    Of course I'm sure...that doesn't mean I'm right.....

    "There's no sense being stupid unless you show it."

    "that was like trying to teach a goldfish how to play basketball over the phone."

  16. #16
    We have met the enemy...
    Reputation: paredown's Avatar
    Join Date
    Oct 2006
    Posts
    7,847
    Quote Originally Posted by Touch0Gray View Post
    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....
    "There are two novels that can change a bookish fourteen-year old’s life: The Lord of the Rings and Atlas Shrugged. One is a childish fantasy that often engenders a lifelong obsession with its unbelievable heroes, leading to an emotionally stunted, socially crippled adulthood, unable to deal with the real world. The other, of course, involves orcs."
    John Rogers

  17. #17
    RoadBikeReview Member
    Reputation: Christine's Avatar
    Join Date
    Jul 2005
    Posts
    15,009
    Let's see, there's a Street View shot of it.........bah, can't edit it...........

  18. #18
    half-fast
    Reputation: 10ae1203's Avatar
    Join Date
    Jan 2007
    Posts
    7,137
    The guy in the picture is parging the concrete block wall.

    Attachment 318240

    Pointing, aka tuck pointing, is the act of replacing the mortar in the tooled joints between the masonry units, whether block, stone, or brick.

    silicone sealing vs repointing-best-parging-basement-walls.jpg
    Last edited by 10ae1203; 03-08-2017 at 12:58 PM.

Similar Threads

  1. DIY Silicone grippers?
    By jnbrown in forum General Cycling Discussion
    Replies: 4
    Last Post: 08-16-2015, 04:02 PM
  2. leg gripper options other than silicone
    By melusive in forum General Cycling Discussion
    Replies: 8
    Last Post: 06-29-2011, 03:18 PM
  3. Seam sealing a tent.
    By Antonio_B in forum The Lounge
    Replies: 28
    Last Post: 06-17-2010, 11:06 AM
  4. Self-Sealing Tubes for CX
    By southpointcycles in forum Cyclocross
    Replies: 5
    Last Post: 12-18-2009, 08:28 AM
  5. Sealing sidewalls
    By alem1583 in forum Cyclocross
    Replies: 3
    Last Post: 10-15-2007, 02:30 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •