Chimney Crown Repair/Replace

Merc1973

Member
Oct 14, 2016
26
MD
As I was cleaning my Chimney liner to prep this season, I noticed my crown is in disrepair. It looks to be poorly done and very thin, even without expansion joint around tile flue. It's beyond caulking since I can lift out loose chunks with my finger. It looks like it has fiberglass in the mix... My house was a foreclosure, so probably one of the many hack repair jobs hired out by the bank i have noticed since we moved in.

A few questions:
-What type of sand concrete mix is recommended?
-I heard about adding latex additive for waterproofing?
-Whats the recommended depth?
-Make the wood form to add a rain drip edge or leave as is?



 

Woody Stover

Minister of Fire
Dec 25, 2010
10,781
Southern IN
I used "crack resistant" concrete, no latex, and I haven't put any coating or anything on the 'crete. Here's a link to my thread. Shoulda got more pics as I went, but I was short on time and had to keep moving. Sounds like you watched some videos already. The middle one posted was pretty good. https://www.hearth.com/talk/threads/time-for-a-new-chimney-crown.156629/
 
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bholler

Chimney sweep
Staff member
Jan 14, 2014
19,050
central pa
As I was cleaning my Chimney liner to prep this season, I noticed my crown is in disrepair. It looks to be poorly done and very thin, even without expansion joint around tile flue. It's beyond caulking since I can lift out loose chunks with my finger. It looks like it has fiberglass in the mix... My house was a foreclosure, so probably one of the many hack repair jobs hired out by the bank i have noticed since we moved in.

A few questions:
-What type of sand concrete mix is recommended?
-I heard about adding latex additive for waterproofing?
-Whats the recommended depth?
-Make the wood form to add a rain drip edge or leave as is?



You want to make a form and pour an overhanging concrete slab. We use acrylic additive and reinforcing fiber.
 
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Merc1973

Member
Oct 14, 2016
26
MD
I used "crack resistant" concrete, no latex, and I haven't put any coating or anything on the 'crete. Here's a link to my thread. Shoulda got more pics as I went, but I was short on time and had to keep moving. Sounds like you watched some videos already. The middle one posted was pretty good. https://www.hearth.com/talk/threads/time-for-a-new-chimney-crown.156629/

Thanks. I did not realize how many bags of mix it will take. I have 3 flues in my Chimney, I did not measure it yet. I may rethink how Im going to bring up 80#bags com mix a ladder. :eek:
 
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spudman99

Member
Jan 26, 2018
175
Yardley, PA
I did my crown last week, 22' x 26' that was in disrepair. I did not make an overhang as I should have, although there was not one there originally and the crown lasted 37 years. I used 45lbs of sand mix and built up the outside edges about 2" to less than 1/2" by the former clay liner. Installed stainless cap for my liner so I was trying to remove the steep slope to allow a better installation.

Mixed the cement in a 5 gal bucket and carried that up the ladder 35'. Wasn't too bad, took my time and made sure I had safe footing.

*will add photo later**
 
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Merc1973

Member
Oct 14, 2016
26
MD
OK, more details. It's a 78"x25" chimney with 3 flues, house build in 1973. The current crown is deeper than when I first looked (it was getting dark). It's been skim coated with fiberglass reinforced cement mix, and deep repairs at the edges. There is plenty of moisture underneath the original crown so I'm glad I'm getting this done this year. Some cinder block is quite crumbly too. Looks like some of the bricks on the top row will need to be set/mortared as they are loose. I don't want to create more work so I'm more careful with the sledge and chisel and using the hammer-drill more around the flue tiles. The far right upper chimney tile just lifted right up, with my hand only, I'm surprised a strong wind didn't blow it off with the stainless steel cap. Hopefully I will do a better job than those hacks who "repaired" this back in 2013. I'm still undecided about forming a drip edge.





 

spudman99

Member
Jan 26, 2018
175
Yardley, PA
Dang that's a big job. Be safe while you are working there.

I would probably avoid a drip edge with the brick corbels. Not sure if it would look good, but then again who looks up at chimneys from the ground and knows how they should look. Adding a drip edge is more work forming the frame, but is probably the best way to go. You do have quite a bit of cement to move up there, multiple 5 gal buckets. Don't forget to add an expansion break around the clay tiles and the cement crown.

Know this that when you go to sell the property, the home inspector will not ding you then for the faulty crown and save you having to hire someone on short notice to fix that mess that existed before. So you save money now, and even more later had you not undertaken this job.
 
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bholler

Chimney sweep
Staff member
Jan 14, 2014
19,050
central pa
In this case I would take down the top course of brick and pour an overhanging crown on top of the band. It looks much better proportionately than having the course step back in then out for the crown.
 
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Merc1973

Member
Oct 14, 2016
26
MD
Dang that's a big job. Be safe while you are working there.

I would probably avoid a drip edge with the brick corbels. Not sure if it would look good, but then again who looks up at chimneys from the ground and knows how they should look. Adding a drip edge is more work forming the frame, but is probably the best way to go. You do have quite a bit of cement to move up there, multiple 5 gal buckets. Don't forget to add an expansion break around the clay tiles and the cement crown.

Know this that when you go to sell the property, the home inspector will not ding you then for the faulty crown and save you having to hire someone on short notice to fix that mess that existed before. So you save money now, and even more later had you not undertaken this job.
Thanks. I hate heights, but I do feel safe here, I will not venture to the exterior side of the chimney unless I have to. I have a 4 ft ladder leaning on the chimney on the roof.

Looks like I will need just under 3.5 cubic ft. of mix if I make it 3" deep. That's a lot to haul up, about 6.


In this case I would take down the top course of brick and pour an overhanging crown on top of the band. It looks much better proportionately than having the course step back in then out for the crown.
Hmm, sounds like more work. I think its going to be without an overhang. Thanks for the idea.
 

spudman99

Member
Jan 26, 2018
175
Yardley, PA
If you are inclined, next spring when the weather warms up, coat the crown and surrounding bricks with a sealer. That should help to shed some water and also make the bricks last longer if they too shed some water. Simple application and wont take long.
 
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Merc1973

Member
Oct 14, 2016
26
MD
Today I finished demo, air chisel is the way to go! Also re laid the top row of loose bricks, its ugly but who's going to see? It was my first time. Re mortared the 2 loose flue tiles and surrounded the flues with foam sil insulation. Tomorrow is pour day.
 

Merc1973

Member
Oct 14, 2016
26
MD
6 bags was perfect. I will cut the sil insulation flush and caulk the gap. In hindsight i should have built a form for a drip edge. Its quite difficult to form an edge with just a float and trowel as it just wants to bulge out. The last bag we used a rock screen to filter out the large aggregate for a smoother top coat. It was in the 50's today and will be a low of 39. I covered it with plastic this evening as it was still quite wet. The temp will be in the 50's tomorrow so I may remove the plastic and see how it dries.

 
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spudman99

Member
Jan 26, 2018
175
Yardley, PA
That looks great although I am not a professional. You should have no problem curing the cement now, cooler nights and some dew will help to retard the drying process. When I did a different crown I included a drip edge. Its a much more involved framing process to include the overhang, add the drip depression and then secure it all to the existing chimney. Yes that is the best practices method, but if your work lasts 20 years and you are not there at that time, it is the new owners problem....hehe.

If you really want to be crazy, next April get a gallon of brick and concrete sealer, hit the top and the brick, focusing on the seam between the crown and brick. Hopefully that should add some moisture intrusion protection but is probably not necessary.
 
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bholler

Chimney sweep
Staff member
Jan 14, 2014
19,050
central pa
That looks great although I am not a professional. You should have no problem curing the cement now, cooler nights and some dew will help to retard the drying process. When I did a different crown I included a drip edge. Its a much more involved framing process to include the overhang, add the drip depression and then secure it all to the existing chimney. Yes that is the best practices method, but if your work lasts 20 years and you are not there at that time, it is the new owners problem....hehe.

If you really want to be crazy, next April get a gallon of brick and concrete sealer, hit the top and the brick, focusing on the seam between the crown and brick. Hopefully that should add some moisture intrusion protection but is probably not necessary.
Don't waste the time or money of sealing it. Just do it right and it is in needed