Poured Concrete

I have a wall in my basement with some cracks. I have another wall collapse on me. My thought was to get some concrete forms and just pour a solid concrete wall + rebar as added support. So would it work if I simply took the exhaust pipes and ran it down the wall, use an ell to turn upwards, run another section of exhaust, turn up with another ell, run another section of exaust... etc. until I'm high enough up to terminate outside? My thought was why not turn the ENTIRE WALL into a thermal mass. Yes, poured concrete instead of cobb. Will it work?

The wall is about 7-feet tall. So my thought was to have three runs of exhaust traveling the entire 50-feet and then back (total of 150-feet)

Michael; We / You need way more information. To start ,let me ask if you have a copy of ianto evans book "rocket mass heaters" ? If not then you need to get a copy . An 8" system can push 50' of horizontal piping , but each 90 degree turn is a 5' deduction , so a 150' run ain't happening... You "could" use a concrete wall as a mass ... but only if its insulated from the earth on the bottom and sides , no exposure to the outside air without insulation also. Better to build a foundation wall for the house , then insulate your mass inside of that. Building your rmh in the basement is not recommended as well. RMH do work ! But only if they share a cherished place in the center of your living area , not down in the basement.

Michael Young : Welcome to Permies.com / Richsoil.com,and a Big Welcome to the Rocket and wood stoves Forum Threads, and the Cob Forum ! 28,000 Fellow
Members World Wide mean you can find someone here 24 / 7 who wants to talk about what you want to talk about !

location and house size, we have to know your climate and the minimum area you want to heat to be able to help you!

Why do you want to put Your rocket mass heater RMH in your basement? are you spending hours there everyday, like an office, work room or rec room?

Your RMH is a space heater, needs to be placed where you actually want its heat, preferably within the very heart of the home, and not located in a distant part of
your home where tending to its needs becomes a drudges task, never well performed,ignored, hated, and finally only able to serve you as well as you serve it !

The largest size RMH feasible for home use and Owner built is an 8'' system, its maximum amount of horizontal run is 50', and we subtract 5' off of that distance
for every 90º Elbow you use, your plan requires 6 elbows or 30' before you hook into your final vertical chimney !

It seems obvious that you are talking about exterior walls of your basement, without a serious amount of insulation applied to the outside of those exterior walls you
will be pumping most of Your heat energy out through that wall and warming much more of the earth around your house than the inside of your house! Remember,
air is an insulator, earth is a great conductor of heat energy and wet Earth is a Fantastic way to transport that heat away from your house !

There are several limitations to the use of Concrete both in the RMHs Burner Base and the first 4'-5' of the Thermal mass, where it is exposed to temperatures that
can destroy the physical integrity of any Portland based Cement/Concrete !

If you want to learn how to use the extraordinary give to man that a carefully planed and built RMH can be, Creating a hand-sculpted piece of Art, built-in furniture
that is capable of warming you and whole families yet to be, becoming a multi generational heart of your home, you have come to the right place.

We love helping future Rocketeers!

Right now if you are ready for that commitment, please go to Rocketstoves.com to Download a PDF Copy of the Brand New Third Edition of Rocket Mass Heaters.
With 100,000 + RMHs made world wide, this is 'The Book' most RMHs were made following the pages of this book, and 95% of all the 1st time builds (that worked)
Were made following this book. Here you will learn the simple vocabulary needed to talk with Your fellow members and understand the RMH, and its Sizes, shapes,
material needs, and the orientation of its parts, to themselves and the whole !

'The Book' will save you Time, money, and hours of frustration that a clear understanding of the basic concepts saves you from ! You are standing on a crossroads,
take this step forward and you will not be alone in your build until you are happy with it ! We Have many members here who are building 2nd and 3rd RMHs

For the Good of The Craft ! Big AL

Because I have a basement and I live in an 80-year-old house, I don't know that the floor joists will hold 2-tons of thermal mass. That's the only reason I was thinking to build the RMH in the basement. But I have a GIANT kitchen (15ft x 35ft) and part of that kitchen sits over a crawlspace area. So I'm thinking it makes sense to get under there and put blocks under the floor joists and then I can have a concrete truck pump in concrete so the floors absolutely *will* be able to support all that weight. Because you guys are right. it doesn't make sense to have the RMH in the basement. My dilemma was how to support 2-tons on these floors

Simple... you don't support the two tons of mass with your existing floor joists

Your kitchen with crawlspace is perfect for the job. Put concrete pads and block piers in the crawlspace in the right locations to support the mass, and you will be fine. You could either cut out the wood framing and flooring in a certain area and frame the remainder of the floor around it, or use the masonry piers to support the existing framing, whichever makes more sense in your particular case. The "masonry from the ground up" approach does minimize the need to protect old wood from heat. A basement area with concrete piers is feasible but obviously more material expense and possibly cutting into useable space.

As far as the amount of footings you need to support two tons, it may not be as much as you think. Even poor soil (clay or loose sand) can be rated for 2000 pounds per square foot, so allowing say a 24" x 16" footing at each pier with one or two piers for each ton of finished weight will give lots of safety margin.

Allen, et al, has given some great advice thus far...

I have many pots in the fire currently and this conversations seems well covered. I can get into more specifics when I see photos of the "final choice" for location. I will add that OPC (concrete) is not the solution in most cases and can almost always be done using more natural and less environmentally damaging material (and industry) than found in OPC.

If you do go with the kitchen...and the crawl space is actually a crawl space...I would recommend removing the floor and taking the support all the way to grade level. There is better support to the design and also some potential for a more massive design (ergo more thermal mass) with a less intrusive presence in the living space. If you haven't read the post here on gravel foundations and Ondols, I would recommend them.

Good luck,

j

Download a PDF Copy of the Brand New Third Edition of Rocket Mass Heaters

'The Book' will save you Time, money, and hours of frustration that a clear understanding of the basic concepts saves you from !


Great advice. I ordered the book. Can't wait to build this thing. Thanks

The reason I'm wanting to use poured concrete is because I fell out of an attic while holding a water heater and did serious damage to my back. So the idea of manually collecting and mixing and heaving several tons of cobb just isn't something I'm going to be able to do. But I could probably handle setting up a form and calling a concrete company to pump in concrete for my thermal mass. I know. Not the purist method. But I don't have the help to go with cob.

I am afraid, because of the nature of masonry heaters of all types, an OPC version (for multiple reasons beyond the environmental ones) is not going to work nor be a very good plan. I can respect, having a physical limitation, and that must be very frustrating, yet it won't make a medium like OPC perform outside its very limited context. I would suggest that if you can hire a concrete contractor to come and pour concrete at its current "yard price" that you may be able to find unskilled labor for not much more to do this job to your specifications with the correct materials.

Regards,

j

Michael Young : As long as the kitchen area comes from that same era and its bones, the original floor joists are in good shape all we need to know is their
size the length of the distance they span and how close together they are measured from center of the joist to center of the joist, Again if everything is still
in good shape the way the weight will be spread out the load is much like a waterbed, even a Crappy 40 year old house can be expected to take that !

I suggested the Download version simply because it was an instant download allowing you immediate access to the material and an easy way to start getting
ready for this project, getting under and bracing up a floor is well covered in the book!

As Jay C. White Cloud told you there are multiple problems with Cement/Concrete, anything you can get in a truck is portland cement based and while it can be
used for the Thermal Mass bench no Portland based Cement can be used for the high temperature areas of the Rocket Burner Base which will be approximately
3' by 6 foot and shaped like an old fashioned light bulb or even more old fashioned Keyhole !

After you have a location within the kitchen for a Rocket, we need to figure its shape and layout, the distance off of the floor and away from walls, and subtract
20% for the mass of the pipes, this will give you a number of Cubic feet you will need, this will most certainly be less than a full load! You will ether pay a
minimum price they will charge for a part load or have a secondary project like the threshold of a barn or in front of your garage doors! or the end of your
driveway!

Also important, where is your septic tank and leachfield, you don't want to find out in the middle of your project that the cement truck has crushed the leachfield
pipes, or has caved in and is stuck over the septic tank!

the arrival of a Concrete-mix truck in your drive way will not go unnoticed, this will probably bring a visit from Your local code enforcement officer! THis can be
the death of your whole project !

This is enough to think on right now, we still need your location climate and minimum amount of space you are hoping to heat !

For the good of the craft ! Big AL