Front Vent/Chimney base questions

[thebadger]

Gang,

A couple of these questions are in my building "blog" but wanted to post here as well...

1) Should I add a row of bricks (on their side) to the sides of my vent walls for extra support? I'll have 8 ft of duravent chimney on top to clear my pergola. I thought it weighed more but a 2 ft section was about 8-10 lbs (so I'll have about 40 lbs of chimney). I'm thinking the arch will support it but I know others were concerned about weight of just a 4 ft section?

2) Any issues with using that "black fireplace caulk" to seal the metal chimney to the firebrick instead of using HS? I'll then use tapcon screws/brick wedges to keep it in place.

3) On the bottom of my chimney plate there is a 1-inch lip that hangs down. So I have a square firebrick opening with a 6 inch round lip inside. Should I fill in this gap between the square brick opening and round chimney section to help funnel the smoke - about 1/2 - 1-inch gap? (FYI - I still need to fit the bricks so they will only be a small gap between all 4 sides.)

Thanks
Dick
'thebadger'

[Ken524]

Originally Posted by thebadger

2) Any issues with using that "black fireplace caulk" to seal the metal chimney to the firebrick instead of using HS? I'll then use tapcon screws/brick wedges to keep it in place.

I used CanuckJim's technique (the second time) to attach the chimney mount. Drill 4 Tapcon holes in the bricks to line up with the chimney mount holes. Put a layer of insulating blanket between the bricks and vent, screw the vent on snuggly (but NOT tightly). Works a treat!

3) On the bottom of my chimney plate there is a 1-inch lip that hangs down. So I have a square firebrick opening with a 6 inch round lip inside. Should I fill in this gap between the square brick opening and round chimney section to help funnel the smoke - about 1/2 - 1-inch gap? (FYI - I still need to fit the bricks so they will only be a small gap between all 4 sides.)

I didn't mess with it. Just drop the round peg into the square hole and screw it down. The insulation will keep it from leaking. The laws of physics will assure the smoke finds it's way up the stack.

[thebadger]

Ken,

Do you need to seal the blanket so it's not exposed in the vent area or is it okay to spill in? I was thinking of the black goo on the inner edge then the blanket on the rest of brick... Just concerned about the blanket being "exposed."

Thanks
Dick

[biondoli]

Dick looking at the way you built your arch, any weight you put on top will be distributed on the side walls of the arch; with the weight you are going to put on top, I would reinforce the arch sides --buttressing new word I learned, I thought it meant "cladding"!

[Ken524]

Dick,

If the blankie is sandwiched between the chimney mount and the brick, it should be fine. I don't think it's going to shred, or fall apart and fall into the oven, if that's what you mean.

[gjbingham]

Dick,

1, I agree with buttressing the walls. I wasn't going to but finally did with concrete by scabbing forms against the outsides of the walls and vibrating the heck out of the concrete when I filled the forms. Because the top of the entryway is wider than the sides, the dovetail helps lock the concrete in place (I hope). I used 8 feet of Duravent, so my decision was a bit easier.

2) no idea!

3) I agree with Ken. Make sure that it is a slightly loose fit - the round lip in the square hole. Others have had problems with tight fitting ones when the oven heated up. The expansion of the metal cracked the surrounding bricks.

[biondoli]

Dickregarding question #1 it looks like all agreed buttressing
#2 "black fireplace caulk" if it is high temp resistant I don't see any problem...any specific reason you don't want to use HS? It worked great for all of us.
Then I have decided to not put screws on top of the anchor plate, my decision was based on the fact that bricks are very hard and consequently very fragile, and any stress would easily break them, that's why I added some L bricks here the photo.
I added also a pic of my anchor transition, I did a tight fit and so far no problem, my dome cracked but not the chimney. On top of it I put blanket and pelcrete to allow up and down expansion.

[thebadger]

Biondoli,

Thanks
I'll take the advice and add some extra bricks to the sides - they'll be hidden anyway so it won't matter.

I heard HS wouldn't really do a good job adhering metal to brick. I do like what you did with the angle bricks. I just don't have as much surface area... I might use a combination of the two...

Dick