Chimney Primer

[blacknoir]

Re: Chimney Primer

If you build a brick chimney around a clay flue, do you fill the 1" gap around the flue with cement or something else? Or is there some other way to keep water from dripping down between the flue and chimney wall?

[karl]

Re: Chimney Primer

Hello Shay.

You definitely do not want to fill that void with cement! The clay flue need to move as it will expand during heat-up. The void is normally air-filled (sometimes filled with stone fibre wool) and the closing of the void is done on the top of the chimney by a suitable hat.

The closing also need to take into consideration the lenght-increase of the clay flue when heated.

regards from karl

[mfiore]

Re: Chimney Primer

Karl, what about filling with vermiculite/concrete insulating material that is used to cover domes? Would that be compressible and allow for expansion (seems to work over domes)?

[karl]

Re: Chimney Primer

Mike.

I guess vermiculite only will be Ok. The clay flue will need to expand in the axial direction (mainly) so you must allow for movement between the flue pipe and the brick chimney. Radial expansion is not enough to worry about. Why fill anything in the void. Air is by far the cheapest "fill"!

regards from karl

[blacknoir]

Re: Chimney Primer

Forgive my ignorance but does anyone have a picture of a suitable hat that can be used to go over a clay flue and brick chimney? everything I've seen just covers the flue and not the surrounding space between the flue and chimney..

[karl]

Re: Chimney Primer

Hello Shay.

There is a picture of my build in this thread which shows the chimney hat I have installed. It is predesigned and sold by the vendor which provides the standard chimney bricks. But it is a simple design. I guess you could also consider to use natural stones (slate?). Just remember to hav a few cm gap between the end of the inner flue pipe and
the hat (for lenght expansion).

karl
http://www.fornobravo.com/forum/atta...ssed-oven1.jpg

[mikes334]

Re: Chimney Primer

I found everything, including a chimney cap, for my duratech chimney project at chimney liner depot.