Flat roof install - What chimney support should I use?

[PJF1313]

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Good Monday evening! (even thou it's MY Friday ;-) )


I'm kicking around the idea of installing another stove in our den/living room/game room.

The Overview -

The house is a 1918 ranch. The attached garage was remolded into an apartment for the former
owners' father in the late '70's/early '80's. 2 x 6 walls; 2 x 10 (12 maybe - long span) ceiling.
This past summer we replaced the roofs, both on the main house and the apartment. The old
hot tar was replaced with 1-4" of tapered ridged Styrofoam insulation, due to poor drainage. It
now has an EPDM rubber roof. It's about 28' wide and about 16' deep - a single piece of rubber.
There is NO attic above or crawl space below.
The wood floor will need a hearth built; it's over 3/4" ply over 2x4, on their side (sleepers)with
homasoap (sp?) between the sleepers, over 1/2" foil cover ridged Styrofoam insulation, all over at
least 4" of poured concrete over soil.


The Question -

What kind of chimney support box should I use - A pitched roof (1in 12 to 7 in 12) or a cathedral
support? Since there is no attic, I would ASSume that all the support will have to be installed
inside, under/around the sheet rock. I know that there is at least 6" of fiberglass insulation up there,
so I guess that I'll need an insulation shield also, correct?
Also, would it be necessary to have the roofers come back and flash around the flashing,
due to the EPDM roof?

Thank you for all your help. Hearth.com is an insurmountably source of information with all your inputs
and ideas!

 

[MountainStoveGuy]

what brand of chimney are you looking at? If its simpson, i would install a 9438A roof support.

If you install two stoves in the same level of the house, they can compete with make up air, and could cause problems if both stoves are working, or smell problems if one stove is working and the other stove is providing make up air.

I would have edpm roofers to come up after the installation and glue that flashing up with the proper stuff. EDPM can be a bi*ch.

 

[Hogwildz]

.
.

Good Monday evening! (even thou it's MY Friday ;-) )


I'm kicking around the idea of installing another stove in our den/living room/game room.

The Overview -

The house is a 1918 ranch. The attached garage was remolded into an apartment for the former
owners' father in the late '70's/early '80's. 2 x 6 walls; 2 x 10 (12 maybe - long span) ceiling.
This past summer we replaced the roofs, both on the main house and the apartment. The old
hot tar was replaced with 1-4" of tapered ridged Styrofoam insulation, due to poor drainage. It
now has an EPDM rubber roof. It's about 28' wide and about 16' deep - a single piece of rubber.
There is NO attic above or crawl space below.
The wood floor will need a hearth built; it's over 3/4" ply over 2x4, on their side (sleepers)with
homasoap (sp?) between the sleepers, over 1/2" foil cover ridged Styrofoam insulation, all over at
least 4" of poured concrete over soil.


The Question -

What kind of chimney support box should I use - A pitched roof (1in 12 to 7 in 12) or a cathedral
support? Since there is no attic, I would ASSume that all the support will have to be installed
inside, under/around the sheet rock. I know that there is at least 6" of fiberglass insulation up there,
so I guess that I'll need an insulation shield also, correct?
Also, would it be necessary to have the roofers come back and flash around the flashing,
due to the EPDM roof?

Thank you for all your help. Hearth.com is an insurmountably source of information with all your inputs
and ideas!

You can use the square box, it is made for both flat & cathedral ceiling installs. This one will extend into the thew roof cavity, which should have some kind of roof rafters, and you can cut it's height to fit to the underside of the rood deck. Thus doing the job of the insulation shield, so no additional insulation shield needed.
Yes you will need the metal outside flashing pan wrapped in EPDM flashing after install.

 

[PJF1313]

MountainStoveGuy -

I was going to use Selkirk, only because I used them before. The stoves would be in two
"separate" areas of the house - no less than 2 doors and 4 steps separating them (I hate
the cats playing pinball with me - I can't see the silver ball over their big behinds )



Hogwildz -

I couldn't remember if you where the resident roofer ;-) Does the square box also require
the prerequisite of 2" clearance from combustibles? I am kind of scared of the foam they used
to make up the pitch on the roof. Or do I cut the rubber and the foam to the outer edge of the
round interior of the chimney flashing?

Thanks again guys.

I'm only kicking around the idea because of O's rebate. The Atlanta stove has it's days numbered,
the Jotul should be here soon. Does anyone need a 300 pound counter weight, anchor, or an
out-door space heater ?!

 

[Hogwildz]

MountainStoveGuy -

I was going to use Selkirk, only because I used them before. The stoves would be in two
"separate" areas of the house - no less than 2 doors and 4 steps separating them (I hate
the cats playing pinball with me - I can't see the silver ball over their big behinds )



Hogwildz -

I couldn't remember if you where the resident roofer ;-) Does the square box also require
the prerequisite of 2" clearance from combustibles? I am kind of scared of the foam they used
to make up the pitch on the roof. Or do I cut the rubber and the foam to the outer edge of the
round interior of the chimney flashing?

Thanks again guys.

I'm only kicking around the idea because of O's rebate. The Atlanta stove has it's days numbered,
the Jotul should be here soon. Does anyone need a 300 pound counter weight, anchor, or an
out-door space heater ?!

The box already makes up the required 2" clearance. So, basically you would trace the outside of the box to the bottom or top side of the roof, cut an "X" in the EPDM from corner to corner. Leave the EPDM intact other than cutting the "X". cut the complete roof decking & insulation out so the box will pass through, take hand brakes that you can buy at Home Depot, bend a 3" flange on the box end on all 4 sides. Flap the EPDM down into the hole along side the outside of the box, set the newly made flanges on the box that you made flat to the top of the EPDM. Screw or nail down through the flange, closer to the outside edge. Then the roofer will take the metal base flashing, and install it. Before he sets it in place He should be putting a bead of either in seam sealant or water cut off mastic on the roof surface under where the base flashing will rest against the roof surface.
This is a back up in case the EPDM flashing should ever fail, this will stop water from flowing under the base flashing and down into the hole. He will then flash the metal base flashing with uncured EPDM flashing. And use lap sealant on all edges & intersections of the uncured flashing.
When you buy the support box, don't forget to figure one high enough to extend through the cavity from the room ceiling to the roof surface and also add the needed 3" through the roof for the 3" nailing flanges to be made.
If you need better details, just lemme know. The roof should know all this if hes worth a damn. If he don't, find another.

 

[PJF1313]

The box already makes up the required 2" clearance. So, basically you would trace the outside of the box to the bottom or top side of the roof, cut an "X" in the EPDM from corner to corner. Leave the EPDM intact other than cutting the "X". cut the complete roof decking & insulation out so the box will pass through, take hand brakes that you can buy at Home Depot, bend a 3" flange on the box end on all 4 sides. Flap the EPDM down into the hole along side the outside of the box, set the newly made flanges on the box that you made flat to the top of the EPDM. Screw or nail down through the flange, closer to the outside edge. Then the roofer will take the metal base flashing, and install it. Before he sets it in place He should be putting a bead of either in seam sealant or water cut off mastic on the roof surface under where the base flashing will rest against the roof surface.
This is a back up in case the EPDM flashing should ever fail, this will stop water from flowing under the base flashing and down into the hole. He will then flash the metal base flashing with uncured EPDM flashing. And use lap sealant on all edges & intersections of the uncured flashing.
When you buy the support box, don't forget to figure one high enough to extend through the cavity from the room ceiling to the roof surface and also add the needed 3" through the roof for the 3" nailing flanges to be made.
If you need better details, just lemme know. The roof should know all this if hes worth a damn. If he don't, find another.

Thanks Hogwildz.

Just the the foam got me nervous/scared with the C to C. As I was saying, we're just kicking the idea around now. IF we do go with it, it would most likely be in the spring - the easiest time of the year for me to take off of work.

Again, thank you.