Chimney Question.. Thimble Placement

I've started building my chimney. I have some leeway as to where the thimble lands in the chimney. Is there any advantage to have it a few blocks higher as opposed to a few blocks lower? Lower will save me some stove pipe, but higher is OK if it's better for some reason.

Not sure it makes any difference Fred. My daughter's mason just finished their chimney & put the thimble about 5' high off the floor. Just a round hole through the cement wall with a clay liner. Anyone know the code requirement in Mass. to connect the stove pipe to this clay thimble?

My thoughts are: Thimble as high as possible, while keeping the required distance from the ceiling. You'll have more room for a taller stove and/or baros, etc.

Devil: Once the thimble is in place, I don't think there is much more that can be done, other than jambing the stove pipe in the thimble and touching off the fire.

Dallas wrote:Devil: Once the thimble is in place, I don't think there is much more that can be done, other than jambing the stove pipe in the thimble and touching off the fire.

No mechanical fasteners are required?

I'm old school .... never have seen anything like that used. You could put a 100# anvil on the floor and tie a cable to it from the pipe.

Dallas wrote:I'm old school .... never have seen anything like that used. You could put a 100# anvil on the floor and tie a cable to it from the pipe.

I'm serious. The town will be coming out to inspect the installation when it's all hooked up & I'm wondering if there are any Mass codes that require a mechanical connection of the stove pipe to the wall thimble? (sorry Fred..Not trying ti hijack your thread but figured this was pretty close to the topic & we do need an answer b4 the inspector comes out)

Double post

You could put a 100# anvil on the floor

Looking for one?? Is the thimble a clay pipe? I don't think there's much you can do except make sure there's a good amount of the stove pipe slid into it.

Wood'nCoal wrote:Is the thimble a clay pipe? I don't think there's much you can do except make sure there's a good amount of the stove pipe slid into it.

Yes John...It's a clay pipe cemented into a 10" thick foundation wall. No mechanical fastener I required? (I wouldn't even know how to do it, short of masonry anchors drilled into the wall??)

I don't know what may be required by code, but drilling holes in a clay thimble and fitting some screws through into the stovepipe isn't a big problem, I have never seen it done, though.

Freddy wrote:I've started building my chimney. I have some leeway as to where the thimble lands in the chimney. Is there any advantage to have it a few blocks higher as opposed to a few blocks lower? Lower will save me some stove pipe, but higher is OK if it's better for some reason.

I would put it higher. If your boiler is near the thimble this allows you to run a steeply sloped stove pipe between the boiler breech and the chimney thimble. Hopefully this minimizes the adjustable els needed down to two. This will keep the flue gas velocity up carrying the ash propelled by the A-A combustion blower to the chimney where it can fall to the chimney's clean out or fall back to the boiler cyclone. I don't buy the design criteria to have tee clean outs for appliances with forced combustion blowers. I believe having a low obstruction flue gas path is more desirable.

Devil505 wrote:I'm serious. The town will be coming out to inspect the installation when it's all hooked up & I wondering if there are any Mass codes that require a mechanical connection of the stove pipe to the wall thimble?

The stovepipe is cut so you can jam at least a foot into the thimble, do not allow it to enter the chimney itself! It should fit snug and if it has gaps seal them with stove cement. No mechanical fastener is required to my knowledge and I have never seen or heard of one that could be used. I would not drill the thimble in any case.

Agreed, Ian. I've never seen the stovepipe fastened to the thimble, but you never know what an inspector will want done.
As long as the pipe fits into the thimble properly and is sealed at the thimble it should satisfy the inspector's requirements.

My brother in law is a sheet metal mechanic. He put my pipe together. He put two holes in the clay thimble with a hammer drill and fastened the pipe to the thimble with self tapping screws. Not sure if it was necessary but he said he didn't want to take any chances.

billw wrote:He put two holes in the clay thimble with a hammer drill and fastened the pipe to the thimble with self tapping screws.

Drilling into clay?.......Is clay strong enough for that without breaking?