attaching a chimney cap to a clay flue

[Caleb]

I was hoping for a little advice on the best way to attach a chimney cap to a clay flue. I am planning to have my local metal shop fabricate a cap.... essentially, the cap will be a rounded piece of iron and I was thinking I'd have them drop four prongs that I could attach to the clay flue with nuts and bolts. Is this a bad idea? Does anyone know how easy/difficult it is to drill a small hole in a clay flue?

Thanks!

[dmun]

Re: attaching a chimney cap to a clay flue

You might start by looking at the commercial chimney caps, which are sized to fit the two main flue tiles, and see how they clamp to the edge of the flue.

There's no reason you couldn't drill through the tile, but it seems like a potential freeze/thaw problem, if the hole gets wet.

[Les]

Re: attaching a chimney cap to a clay flue

Caleb,

What are you planning on covering the flue with? I used brick and set in some lead anchors to screw into. You can drill into the liner with no problem - my concern is that it's pretty brittle and if you crack it, well, that would be bad...

Les....

[Caleb]

Re: attaching a chimney cap to a clay flue

Hi guys,

Thanks for your speedy response. Freeze/thaw is definitely something I should consider. Flagstaff is at 7,000 ft and experiences a nightly freeze/thaw cycle about 80% of the year.

I wasn't planning to cover the flue... is that a bad idea? I've gotten the oven chamber up to ~300 degrees and the chimney did a great job of funneling the smoke. I assume one reason to cover the flue is to insulate it but if it funnels the smoke, is that necessary?

I've been considering having the shop fabricate a cylinder with an outer diameter = inner diameter of the flue. If the cylinder was long enough (1 foot or so), it should be stable in high winds. The cylinder liner would attach to the top cap via 4 prongs. Thoughts?

Oh yeah, here is my Picasa photos of the oven so you know what I am dealing with. I'm a novice at this whole thing, which you may find evident in the photos.

Picasa Web Albums - Caleb

Thanks a bunch, you guys are great!

[amber]

Re: attaching a chimney cap to a clay flue

Caleb, I would cover it if for no other reason than to keep water out of the chimney and dome.

[Chef]

Re: attaching a chimney cap to a clay flue

We had a wind storm of the weekend and can't seem to find our chimney cap...we never even tightened the screws around the clay flue never mind drill holes in it. We were planning on extending the chimney in the spring to improve the draw.

So my advise is DO secure the cap...let us know what you do end up doing!!

[cvdukes]

Re: attaching a chimney cap to a clay flue

Caleb,
Easy way to attach is to have the four prongs made so they slip inside the flue about a foot. If you don't worry much about wind, a friction fit will hold it in place...for a little bit of security, you can use sodium silicate sealer or other heat resistent adhesive...there's a caulk tube material sold at Lowes that'll go to 2000 and is sticky as the dickens... it seems like it adheres metal pretty good to brick once it sets up, so no reason why it won't bond the cap prongs to the inside of the flue.

[BCiliberto]

Re: attaching a chimney cap to a clay flue

Caleb- great looking dome!

isn't that an 8" or 10" round terra cotta flue? Just google "chimney caps" and dozens of suppliers will come up offering hundreds of caps styles-- from about $30 to 300. they usually have set screws or bands which tighten.

probably lot easier , and cheaper, than fabricating... IMHO.

Ben

[amber]

Re: attaching a chimney cap to a clay flue

Les,
Did you make or buy your flue cover? It looks great!

[Caleb]

Re: attaching a chimney cap to a clay flue

Hi everyone,

Thank you for your input. Below is a picture of the design I went with. My local welder is fabricating it for me. I'll likely use some heat resistant adhesive to fully secure it. It should be done in a week or so and I'll let you know how it comes out!

The top of the chimney cap is meant to replicate the San Francisco Peaks, which is also in my backyard.

Thanks again

Picasa Web Albums - Caleb