mjzraz

I had a leaking chimney crown, spalled bricks, deteriorated mortar, etc. There is an existing metal chimney liner installed due to cracked flue tiles before we bought the house. So far I have removed the crown and replaced the top 2 rows of bricks and a few other spalled bricks. I am also grinding out the joints to repoint.

My main question is when replacing bricks that are spalled or loose in the mortar: I have been grinding them out with a 4 1/4" tuckpoint blade and then using the air chisel to pop loose mortar and I have a diamond glitter bit. the problem is that I go to replace one brick and and up with 5 loose bricks all around.
once the mortar has lost the bond with the brick, does is need to come out or can it be tuckpointed back 1"? I am trying to do the least damage, but cracks appear anyway. I don't want to cover up the problem, but i also dont want to do extra work.



crown:


bad row:




south side:

mjzraz

my crown will be like this:


Fiber reinforced concrete with a builtin overhang and drip edge

jomama45

Wow, that's a fairly aggressive job for a DIY'er, but you're doing a nice job from what I can see.

I wouldn't be concerned with a few hairline cracks, they're bound to happen trying to remove one brick here & there. As long as you're tuckpointing the "loose" brick, you'll be fine.

If you're looking to match the existing joints, you'll need a grapevine jointer.

Keep up the good work.

Michael Thomas

Nice to see that you have so many of the cap details right. What appliances are venting into the chimney? Is the metal / clay tile liner is continuous from the appliance vent connectors to the tile projecting from the cap?

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mjzraz

Thanks there have been a few times I have questioned what i was getting into going up on the roof with a harness, tool belt, air chisel, grinder, etc. I thought about renting scaffolding, but bought 7 sections off craigslist for the same amount as renting and they needed minimal work.
yesterday I went to replace 2 severely spalled bricks and ended up with I think 8 total bricks out of the corner. I replaced all but 2 of them before I lost sunlight. I want to get a headlamp to work past 5. My neighbors think I am nuts already.
I have the grapevine jointer... I was thinking of doing that joint on the lower joints. I don't know... it's hard to see that detail up at the top and I liked the water shedding of the concave joints better.
I will be tuckpointing the entire area above the roofline.

mjzraz

That pic is pretty much what i will have. I made wood forms with a 15 deg bevel with a slot rabbited out for a 1/4" strip of wood to be inserted to form the drip. these are 2x4, then a 2x6 will go over that forming the lip.

My question is the sealant to use between the crown and the flue. Would 100% silicone work? Geocel 2300?

The tile liner is continuous from the top of the firebox/flue vent to the top. There is already a stainless steel liner with a dark gray mortar sealing it at the top of the clay liner. This was done by a professional chimney company 10 or so years ago. I believe it was because the clay tiles were cracked. I can see cracks as I open the bricks here and there. I thought about replacing the top clay tile, but they are all cracked so replacing 1 didnt make sense with the liner already there.

There is a brick wood fireplace venting into the chimney. We used it occasionally over the past 10 years.

mem

Maybe the vibrations from the air chisel are knocking the other bricks loose? Scraping, prying or blowing out the loose mortar may save you some grief.

Your crown plans look good but I would like to offer a few suggestions. The bevel idea seems like a good theory, but in actuality it just works to weaken the concrete as it becomes thinner and thinner. A simple step down around the edge would be far stronger and serve the same purpose, as well as be much easier to construct. A drip groove could also be added with a piece of half-inch half round.

The crown needs to float as it will expand and contract at a different rate than the brick. A bond break between the brickwork and crown is essential--either sheet metal or tar paper would be suitable. A gap around the flue is also necessary for expansion. The gap can be filled with sand or oakum once the concrete cures, then caulked with the appropriate sealant. An expansion gap around the underside of the crown, between the brick and the step down, is also a good idea.

I posted a reply a while back in a similar thread chronicling how I went about incorporating all the details in my new crown. I looked it up:

http://www.diychatroom.com/f19/rebui...ney-cap-91516/

It's only been a few years now, but it still looks brand new! I wish you likewise success.

mjzraz

I agree the air chisel can do damage, but I am using it strategically, not going nuts on it. for example, were mortar joints intersect, it usually causes more damage. I can only grind so deep with the 4 1/4" blade. anyway what I believe is the case for most of the bricks in an area is that the bond between the mortar and the brick is broken on all 4 sides and the brick is "floating" but the mortar is bonded to itself locking it from just falling out.
The problem is once the brick is out, there is basically no room for new mortar until I remove the old, which is quite solid, just it wasn't bonded to the brick.

Thanks for the tips. maybe my picture exxagerated the bevel. It's only 15 degrees off of a right angle. I am using a bond breaker to float the crown. I like the idea of the expansion gap on the underside at the stepdown. I can add that without major modification.



Good read. I think I read that before and it gave me some ideas. My info came from the JLC guide to moisture control book.

Pittsville

Just curious... but what's with the stacked extension ladders?

Michael Thomas

One possibility for bond breaker is to use self-adhesive flashing above a metal drip edge, along with a capillary on the underside of cap, as is done on parapet walls under the coping (see image below),

IMO, its preferable to slope the cap, if you are concerned about it structural integrity add a metal mesh reinforcement of the type used in driveways.

The English, who are the authorities on brick masonry construction "to last a lifetime", like to add a "through-wall" in the chimney flashing several feet below the cap.

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Home Inspections, Infrared (Thermal Imaging) Leak Identification and Inspection Services, Roof, Attic, Building, Basement and Foundation Moisture Intrusion and Water Leak Inspections, Troubled Building Consultations - Serving Chicago and Suburbs http://paragoninspects.com/

mjzraz

Nothing - the aluminum one has issues going down, it will go up and I just moved it there temporarily to get it out of the way

stadry

if jomama's happy, i am thrilled to death it looks as if you're thought out the work well & are going about it as we would, too - nice going

mjzraz

So far,so good. I ended up putting a foam board spacer between the brick and the form to create a space to caulk and for it to float.
The only thing that went wrong was I ran out of sunlight and ended up finishing it in the dark @ 10PM ! neighbors must think I lost it.

How long till I take the forms off? I have kept wet towels on it and it's covered with plastic and a tarp. inside I have the flue open and a heater near the chimney. We had a few nice days in the high 60's, 50's overnight. Last night was the coldest @ 32. The next few days the lows are 45 or so.

mem

Looks great mj! I blanketed and plastic wrapped mine too, with a heater in the firebox and it was downright balmy under there every time I checked it. I left my forms on for probably a week and a half or so, but I had much more severe weather at the time.

It looks like you were able to friction fit the forms? Mine was purposely a very tight fit as well, but I stuck some legs under it for insurance, Murphy's Law you know. I don't see any need to caulk up under there either. Your drip ledge will keep it dry.

Nice work, especially if jomamma and itsreallyconcrete and happy!

mjzraz

Thanks. With the foam board around the top row of bricks, the 2x4's fit tight. In addition, I put a couple of screws in just until they touched the brick.
What really locked the forms to each other was the silicone caulk. I got some that skinned in 30 min and was paintable in 3 hrs. I removed forms after 5 days. with all the screws out, it took a lot of gentle persuasion to get the forms off because the caulk stuck really well to the wood.

The only problem is a few spots like this where there was an air pocket and there is a hole in the concrete. can I fill these with something? looks like a place for water to sit and freeze that I don't want: