building a block chimney over a radiant poured floor

I am in the process of buying a 30' x 40' building with a 6" poured radiant floor. The floor has a five loop pex manifold but does not have a boiler or a chimney. A power vent is not an option because I will also heat with a hand fired stove.
Would you cut the floor dig down to ledge and poor a footing? Or would you build a steel frame off the huge H beams on 13' centers???????
I will post some pics....
A center chimney with two or three flues is what I have in mind.


Thanks, Eddie

The possability of the fill sinking would stop me from putting
a chimney on top of the floor with out a footing under it.I hope
the cement doesn't touch the outter walls,It will take a bunch
more btu's to heat when its tight to the slab.
Terry

Put the boiler outside and build around it, Chimneys on the outside with wall thimbles. Enclose with chimney in an insulated chase.

Is that the lower part of the garage the pic's are showing ?

gizmo wrote:The possability of the fill sinking would stop me from putting
a chimney on top of the floor with out a footing under it.I hope
the cement doesn't touch the outter walls,It will take a bunch
more btu's to heat when its tight to the slab.
Terry

The floor does touch the outter walls.....

crazy4coal wrote:Put the boiler outside and build around it, Chimneys on the outside with wall thimbles. Enclose with chimney in an insulated chase.

I need the chimney in the center of the building and would like the boiler in the basement.

theo wrote:Is that the lower part of the garage the pic's are showing ?

Yes, The basement has it's own garage door..

Nice setup !!! I'am asuming you want a block or brick chimney ? I would think that you would need to put a footer in the floor for that,,, just my thought. Hopefully someone with more knowledge will chime in. Are there any other options ,,, the chimney have to be in the center ?

Buy LL AnthraKing 220K with powervent. With the money saved over your very expensive infrastructure here and put it in the bank. Take 10% of that capital saved every year and spend a month in Bora Bora. I just don't get it.

If you need a chimney, then you "need" to have a footer. Do you have any information on how the tubing is spaced in the floor?

You could add on outside the barn with a boiler room.
Go with a stainless that is supported by the structure. (expensive and will rot away)

cArNaGe wrote:If you need a chimney, then you "need" to have a footer. Do you have any information on how the tubing is spaced in the floor?

You could add on outside the barn with a boiler room.
Go with a stainless that is supported by the structure. (expensive and will rot away)

I have no info on the pex spacing in the floor.
At work we have a thermal imaging camra that I could use. I would need to run hot water through the floor though.
If I place a footer in the floor I know at least one loop will be lost...That may not be a big deal in the overall picture.

A full chimney needs a concrete footing. If there is no insulation under the radiant floor I think you'd be OK to land the chimney right on the floor & leave the tubing under the chimney. If there is one or two inches of blue board insulation under the radiant floor I think you might run into issues with the weight of the chimney cracking the floor & crushing the insulation. Perhaps a chimney expert could answer that question. I'm thinking you'd have to cut a larger than chimney rectangular hole in the floor, get lucky and break the concrete from around the tubing, splice it and route it around the new to come footing, do away with the insulation and pour a footing on the Earth. A full chimney weighs a LOT. It must either be part of the full foundation or be an independent part & allowed to settle an 8th of an inch & not break the rest of the building.

All good ideas, Eddie. My 50 years in concrete begs the basic question? What are we pouring on? Is the floor on fill now? Sure it is and hopefully well compacted. However YOU don't know what is under the floor.
It appears that there is ledge close to the surface, but it never is level, so drilling and pinning is an option IF you saw-cut the center section where the new chimney would go.

The interior loop heating area lost is no big deal, but as I look at the structure (man, I'd love to have that one!), the gables are the only logical spots IF you would construct an outside chimney.
The lower side is the logical one, because you could have the chimney with 2 or 3 flues, look terrific, and have a flue on each floor.
Structurally, digging to ledge or digging to solid soil is possible, frost walls on a big reinforced steel footing is VERY cost effective, and building the chimney is straight forward.
Yes, I know all the purists will tell you an exterior chimney won't draft as well, but I'll bet the draft will suck the hair off you head if you stick it the flue.

I understand the desire to go internal here, but saw cutting, demo, excavation, re-pouring won't be cheap either. The 'outside solution' causes NO interruption in the plans for the inside either.
Personally I 'dislike' SS chimneys and at 45.00 a foot plus installation.......nuff said.
This in Maine; coastal Maine.....this is a permanent thing, AND masonry will allow for more than one flue.....at a small cost. I'll go snap a few pics of SS installs locally where they have 4500.00 in parts. OUCH!!!
A nice looking building deserves a nice looking chimney. Core a couple holes for the flues through the existing foundation, and clean-outs can be outside.
Masons are slow around here, keep you ear to the ground Tonto, something good is coming your way.
My thoughts on the floor touching the perimeter....and related heat loss.....well, lets just say you are heating with coal, and it won't make any difference.
The thermal mass you will have in this structure will just amaze you. If it were NG or Propane.....well, you are not that foolish.
I hear you are working on a couple hi=tech 'canoes' up there.....probably in a heated shop.....grrrrrrrrrrrr.

My other thought is that the chimney on the lower side would allow VERY easy access to coal storage, mechanical room, etc. and keep any associated mess off the living area.

Like Wistlenut said. Cutting the slab would be costly and comprimize the pex.
Also having the chimney in the center of the room you will loose valuble floor space on the open second floor.
If you can depending upon floor plans,put the chimney on the outside back side so they will miss the windows,If not either loose a window or move a window,the chimney is more valuable then the windows.
Lay 8" block and fill the cores with vermiculite,that tall of a chimney will have great draw.
Nice garage ,adding insulation and a boiler the garage will be easy cheap to heat.
Chimney that size needs a footer any where you put it.

Calculate the weight of the chimney you want to install. Then use a reasonable factor for the ability of the poured floor to support weight. If the weight of the chimney/square foot doesn't exceed the weight carrying capability of the floor/sq foot then I think you could just build the chimney directly on the existing floor. If you need to spread the weight a bit you could put a reinforced pad on top of the existing floor--but obviously you need to factor the weight of the pad into your calculations.

I put my masonry chimney in the barn directly on a 4" slab--no footer under the chimney. I put a single flue in using 16" masonry chimeny block directly on the floor--no sub-structure to spread the weight beyond the 16" x 16" footprint of the chimney block. With chimney block the load is not even uniformly distributed across the 16 x 16 footprint--the load transfer is only at the perimiter of the block where mortar was placed. Install was done 2 years ago and there have been no problems.

The load capability of a concrete slab poured on well compacted material is typically quite high--think of a heavy vehicle or construction equipment or pallet loads of heavy material that are stored on a concrete slab.

It's all about weight distribution, bigger is better.

Where I live we never even heard of *ledge*...and build things all the time.

Here's something to ponder...
This is just a brief concept, naturally, more details are involved...nay-Sayers, please be kind.

If you can put any value in seeing and knowing what you have below that slab, at your desired chimney location, here is what you can do...
Layout on the floor a suitable grid pattern to do some core bore sampling holes, missing the embedded pipes, of course.
Once the *slugs* have been removed, analyze the sub-soil by digging deeper. If your findings now give you some confidence in knowing that previous *unknown*...then proceed to form and pour your reinforced concrete footer and allow the dug out core holes to be part of the pour with vertical reinforcement in holes being tied to the horizontal....more and deeper holes are better.

Who knows...you may even hit that *Ledge*

If your going to go through all the trouble and cost of a block chimney do it right,,,,, pour a footer for it to set on. Youll be glad you did in the end.