Floor support plans

Anyone know a good formula or a way to a quick and dirty support post calculation?  

I am about to install a masonry heater build that is based off the batch box rocket concept.  My plan is to have this thing pretty heavy.  Maybe an upwards of 6,000 pounds or more in the end.  

I have a chimney in the middle of my main floor away from any walls or furniture.  I plan to basically build a masonry build around the whole chimney about 2.5 feet out from all sides of the chimney(in the shape of a square, but more rounded).  The basic plan is to have a routed portion be a cook top and oven to a tall tower like bell, to maybe a smaller bell, and to about a 2.5' x 6.5' x 2'(Width x Length x Height) bench of sorts.  Nothing set in stone(pun intended).

I have built a J tube style RMH in my last house and used it for two winters.  For that one I cut a large hole in my floor and built a cinder block foundation up from my basement to support the weight.  Which as my first prototype was only about 2,000 lbs about.  Worked pretty well I might add.  Although it took a while to build.

This farm house I have now I wanted to build on top of the hardwood floor instead.  I wanted to skip the step where I cut into the floor for its messy and a pain.  It also seems it would heat sink less to the basement this way as well.  For my old house's basement was cold and the cinder block foundation was built strait up from the concrete floor.  Which stayed fairly cold all winter.

I have the Bonnie heater plans from Erica and Ernie so I understand some good methods of building on the floor to keep proper clearances from the hardwood and what not, but the floor supports is a left concern of mine.  I am not sure where to approach the support calculations standards.    

As for materials can I use two slapped together 2x4s in the proper array and quantity?  Or should I use metal posts, or something better and cheaper?  I guess I am looking for how many posts and what kind per area of weight if you follow.  I am starting this project next weekend so any info would be greatly appreciated.

-Thanks Perma People!

Mathew. Just an idea, cut the floor anyway. Put a bunch of RSJ bellow the level of your actual floor joists. Make a OSB box on top of this, support the RSJs  with piers. And pour concrete in the box. Insulate from underneath, so you don't have the heat going away.

Anyway, you can use the old chimney as mass already. I kike the idea of batch conversions for old fireplaces.

If you could take a few pics, that would be good.

Satamax Antone wrote:RSJ  

??

matthew boersma wrote:

Satamax Antone wrote:RSJ  

??

Uk acronym for rolled steel joist, a metal I beam.

Let me clarify.  What does RSJ stand for?  You said "Put a bunch of RSJ bellow the level of your actual floor joists."


**update: I just googled it.  "rolled steel joist".  I see now.

Honesty I like your idea with the floor hearth concept.  But in reality not cutting the floor is way way way easier, and less messy, and will take me a whole day less to start building.  I really just want to lay the brick on the floor and support it as necessary.  I will add some picks in a short while to give you a better idea of what I have to work with.  

-Thanks.

So a quick reference I came up with that could help narrow the answer to my question.  My overall area of floor should be close to about 7x7.  This include about a 2'x2' chimney in the middle of it all that will be supporting itself from the basement floor on up.  I need to be able to support about 2-4k lbs in that area.  As I add mass and cooking parts I am guess about 6k is a good number to think about.  So in about 49 square feet I need to support that much weight not including the cimney.  It that helps com up with some sort of calculation please let me know.  

-Thanks!

I understand why you're doing this, but the whole thing sounds incredibly risky to me.  At the very least all these DIY modifications will void any homeowner's insurance you might have, and you are messing with both very high heat and high loads in systems that were not designed to handle them.  You could easily burn your house down or cause serious structural harm.

If you're dead set on doing this, get some professionals (at least a structural engineer) on-site to give you advice based on the specifics of your case.  Even the best intentioned and competent advice from people online is a far cry from having a knowledgeable practitioner there in person.

I hear what you are saying, and maybe you are right.  Maybe sticking with the original design I have done before(cutting the floor, and building the foundation up from) may be a more guaranteed option to follow through with.  Although I will say that it just seems like supporting a floor with beams of certain design and quantity isn't all that far fetched of a concept to me.  I was just looking for some simple numbers to work off of so to roughly calculate my load requirements with.  Then I would basically proceed to add 30-50% just to make sure.  I would like to see what others have to say about this too.  I wont start till I have some sort of guarantee mind you.  I am no fool.  Also I may have an engineer friend that could maybe give some solid advice as well.  In the mean time any other thoughts are welcome and appreciated.  

-Thanks!

Matthew,

Personally I would not cut into the floor significantly.  The structural parts of the floor may help stabilize the building laterally, and you'll lose any such stabilization if you cut it.  You might be able to cut small holes in for posts, though, so that the weight of the heater rests on the posts instead of the wood floor.  That might help insulate the wood floor from the heat to some degree, too.

There's nothing far-fetched about supporting the floor with beams and posts, but getting it right can be tricky, and the consequences of getting it wrong are so dire, that an abundance of caution seems warranted.  I'm glad you're being careful!

4 200x200 mm (about 8x8 inches) posts will support this kind of weight no problem, but you need a good solid footing. If your cellar has a thin concrete pad then the posts will want to push through it.. You also need to think about lateral bracing (diagonals).
I really like the attitude of just going for it, but in some situations it's much more wise to take the belt-and-braces approach.

This is one situation where you want the support for the RMH be the last thing standing when the rest of the house has returned to dust.

Also I'd like to echo what Steven said regarding the floor possibly stabilising the building laterally, it's hard to say without seeing it.

The fastest way to do this while not stressing the existing framing would be to cut out the flooring and subflooring over the area in question (a couple hours' work maybe) while leaving the framing as is. Then bring the supports up between the joists and make whatever base the mass will rest on, a couple inches above the joists for heat safety.

Given 6000 lbs load on a 7' x 7' area, four steel jackposts could easily carry 1500 lbs each depending on the particular posts (their rating is given on the packaging); the issue here would be the basement floor. If the floor is solid and reasonably thick, and especially if it is reinforced, it could spread the load to the subsoil enough to give an added load of maybe 1000 psf, which good subsoils can take without sagging but weak subsoils cannot. If anything is substandard, you would get cracking of the basement floor and maybe one or more of the posts sinking a bit.
Doubling the jackposts and putting each on a solid 8x8x16 concrete block or the like would spread the load enough that I would be comfortable with it, though I would still prefer masonry support for the stability. You could even combine methods, having say four masonry columns and four jackposts all spaced out to best spread the load.

Steven Kovacs wrote:Matthew,

Personally I would not cut into the floor significantly.  The structural parts of the floor may help stabilize the building laterally, and you'll lose any such stabilization if you cut it.  You might be able to cut small holes in for posts, though, so that the weight of the heater rests on the posts instead of the wood floor.  That might help insulate the wood floor from the heat to some degree, too.

There's nothing far-fetched about supporting the floor with beams and posts, but getting it right can be tricky, and the consequences of getting it wrong are so dire, that an abundance of caution seems warranted.  I'm glad you're being careful!

I have thought of doing this sort of thing.  I have some good posts available to me for this already.  Great to have a little reassurance my ideas could be valid with enough thought, planing and careful calculations made.  Keep the advice flowing I am getting visions a grand, lol.

-Thanks!

Rus Williams wrote:4 200x200 mm (about 8x8 inches) posts will support this kind of weight no problem, but you need a good solid footing. If your cellar has a thin concrete pad then the posts will want to push through it.. You also need to think about lateral bracing (diagonals).
I really like the attitude of just going for it, but in some situations it's much more wise to take the belt-and-braces approach.

This is one situation where you want the support for the RMH be the last thing standing when the rest of the house has returned to dust.

Also I'd like to echo what Steven said regarding the floor possibly stabilising the building laterally, it's hard to say without seeing it.

Even if I did end up cutting the floor I would not remove the support beams.  Just the flooring basically was my main thought.

Glenn Herbert wrote:The fastest way to do this while not stressing the existing framing would be to cut out the flooring and subflooring over the area in question (a couple hours' work maybe) while leaving the framing as is. Then bring the supports up between the joists and make whatever base the mass will rest on, a couple inches above the joists for heat safety.

Given 6000 lbs load on a 7' x 7' area, four steel jackposts could easily carry 1500 lbs each depending on the particular posts (their rating is given on the packaging); the issue here would be the basement floor. If the floor is solid and reasonably thick, and especially if it is reinforced, it could spread the load to the subsoil enough to give an added load of maybe 1000 psf, which good subsoils can take without sagging but weak subsoils cannot. If anything is substandard, you would get cracking of the basement floor and maybe one or more of the posts sinking a bit.
Doubling the jackposts and putting each on a solid 8x8x16 concrete block or the like would spread the load enough that I would be comfortable with it, though I would still prefer masonry support for the stability. You could even combine methods, having say four masonry columns and four jackposts all spaced out to best spread the load.

Excellent.  This is what I am talking about.  Great info!

-Thanks much!

Here is the top floor pic.  I will be taking out that old hearth and the space heater.

matthew boersma wrote:

Even if I did end up cutting the floor I would not remove the support beams.  Just the flooring basically was my main thought.

Matthew, "french" way would be to pour concrete between the beams!

So to update you all who chimed in I decided I will be cutting the floor by or before this weekend.  Turns out the engineering required is unnecessarily complicated, more expensive, and not without potential issues to simply try to support using arrays of beams.  You all scared me strait so to speak.  The cinder foundation from the basement floor just disperses the weight more even by default than the posts would, and all I need is mortar to do that...  For I have the cinder block already and everything.  I plan to insulate the space between the main mass and the footing from the basement with a nice layer of ceramic fabric to help the heat sinking issue.  

I have started the construction of my 6" batch box core and riser using my old j-tube casted core parts.  So far I have managed to get he burn chamber most constructed.  So I am on my way to once again having a clean burning heat source!  yay!  Thanks for you input all.