diy chimney cap question

[willy r.]

Hello, everybody. Just installed a woodstove, ran the stovepipe into my masonry chimney, and have been using it for the last two days. The draft is great and we're all very toasty. I do not, however, have a chimney cap, so I made my own out of a couple of sheets of stainless steel and a steel frame.

Here's my question: exactly how high should this cap stand over the top of the chimney?

A complication: The chimney has three flues in it but I'm only using one. They all stop 6 feet shy of the chimney top, which means that that the draft runs up my active 8" flue and into a 16"x24" stack, then 6 more feet into the open.

Here's what I read in Domestic Engineering and the Journal of Mechanical Contracting, v. 98, in an article about chimneys: "The opening beneath the cap should be as large as the area of the flue. This area should be provided on each side."

So... to ensure that I don't screw up my draft... Does this mean the cap need to stand 16" above the chimney, so that I get a 16"x24" opening under both of the cap's long sides? That seems crazy to me. If it stands a measly (and more doable) 4" over the top, the total area would be equivalent to the area of the chimney. Is that enough?

Sorry for this lengthy question, I'm sure there's a simple answer...

 

[Fsappo]

I would have the cap about 10" above the top of the chimney, that doesnt fix the other issue you have with the clay tiles falling short. If it was me, I'd feel real nice about making my own chimney cap, buy a 6" liner for $500 bucks and drop it down the chimey. Take your chimney cap and turn it into a top plate that will cover the opening at the top of the chimney with a 6" hole in it for your liner. I'm assuming it is a stove with a 6" flue, I'm assuming it is an 8x8 tile that will have a 6.5x6.5 inside dimension, I'm assuming the tiles arent staggered, which is a tough one consider the chimney was not built properly and I'm also assuming you'd spend money on a liner..but you did build your own chimney cap..

 

[shawneyboy]

It sounds to me that no liner was used.