Refrax Mortar Chimney for Chase Brick

[RCANCILLA]

Hello,

Thanks to the help of a few good forum members, I have reached the chimney and gable roof phase of my construction.

I have the Premio modular oven.

I intend to use the 36" insulated chimney flue purchased through Forno Bravo. Then surround it with brick.

I have 2 questions:

1. Can the vent support the weight of the brick chase?

2. Should I use refrax mortar to lay the brick or can I use S type mortar? I ask this, because I do not know how much heat is actually transmitted from the oven to the vent and then to the chimney chase through contact. I understand the insulated flue itself should not transmit much heat.

[CanuckJim]

The SS flue will transmit very little heat to the chase. However, you should leave an air gap between the flue and the chase. The Premio's cast oven landing will support the weight, but you might be better off using thinner chase material, such as a steel stud box, covered with cement board, then dressed with thinner veneer brick (1" thick). You won't need Refrax for the brick work if you go the full depth route; Type S and sand, 1:3 will work fine, although you might want to go with Type N for a vertical surface. Veneer brick can be pasted on with Thinset Stone & Marble, then the joints can be pointed with mortar once the Thinset dries.

Jim

[dmun]

If you build the chase out of full thickness brick, you should devise a way for the weight of the chimney to be borne from the support slab rather than the top of your dome, particularly if it's more than a few feet tall.

[RCANCILLA]

Thanks for the info. I don't get along well with steel studs so I'm trying to avoid them. Although I find it interesting that so many people here do a great job them.

I am bulding brick and block up from the hearth floor to level with the vent on both sides of the vent. I plan on trying to distribute the weight of the chase across the vent and the two brick sides so that the vent should only have to accept 1/3 of the weight.

Thanks again!

[dmun]

I plan on trying to distribute the weight of the chase across the vent and the two brick sides so that the vent should only have to accept 1/3 of the weight.

Exactly right. You may want to consider bridging the dome with a pre-cast concrete lintel (or a homemade equivalent) so your entire chimney weight is transmitted to the support slab.

[CanuckJim]

You could cast your own lintel out of a material called Kastite, available from, I think, Chicago Fire Brick. It's quite strong and will not have the same expansion/contraction problems as more traditional steel.

Jim

[RCANCILLA]

How about supporting the lintle (concrete or whatever) on the front with the brick wall in front and to the sides of the vent and supporting the lintle from the back with two floor jacks mounted inside the walls and spanning the oven?

I'm afraid to use just the side walls to support the lintle as they are 63" apart and I used 4" wide bock above the hearth.

[dmun]

Well, jacks are expensive, how 'bout stacking up some 4" concrete blocks on the inside of your existing block wall? If you buy the solid ones you can cut them to length with no loss in strength. I'm not convinced, by the way, that your four inch thick wall isn't strong enough to support a lintel, unless your chimney is two stories tall, or something.

[RCANCILLA]

Well, based upon the geodesic dome you built, I'll take your advice. I'll try the blocks.

Don't worry, I won't hold you responsible.

Thanks again!