ByQ masonry heater?

[Seasoned Oak]

30000 BTUs? That wont work for me ,i need 3 times that on a cold day.

 

[DougA]

No. My problem is that I want to build it against an outside wall that is 16' high but tight on other dimensions and one floor only. Not enough sq ft of exposed surface then. The other option is an inside wall where my present stove is but only 10' high. If I ever have a builder here, they will want to put it dead center in the room which would be functionally perfect but my wife and I both think it would look like sh*t. The middle of the room actually would have the advantage offering a fire at 2 levels. Still looks like a furnace in the middle of your house.

 

[DougA]

30000 BTUs? That wont work for me ,i need 3 times that on a cold day.

Check out your BTU ratings. Most stoves are rated as 'maximum BTU' but the real world usable BTU is usually 40-50% less. A furnace in an average house in our area is 75,000 BTU, so 90K is A LOT.

A typical masonry furnace is 150 max on the stone cladding, so you really do need a huge surface area to generate enough BTUs. I know my VC is worthless if I burn it at 400 and wonderful at 700, so 150 is a big leap for me. I saw one masonry heater in northern Italy when I was there a year ago. I didn't even recognize it at the time. It was warm to the touch and that's it. Sure made the room nice though.

 

[Kosmik]

Guess I was wrong about the fiberglass. Guess it makes sense though, R stands for resistance, not exclusion.

Masonry heaters can vary with the shell temps, based on design.
But yeah, they take a lot more surface area than a similar output iron/steel stove. The shell materials can affect that rate of transfer too. That's why you see a big difference in designs based on application/materials. And lots of heated benches/chairs, sleeping quarters. If you have stone on your property, it could probably be designed in and trade $ for sweat. But the type of stone is important as different stones have vastly different heat retention and transmission properties.

Thanks for the info. Unfortunately life got too busy to make the build you told me about. But I'll eventually get to one of the events.

 

[byQ]

Guess I was wrong about the fiberglass. Guess it makes sense though, R stands for resistance, not exclusion.

Masonry heaters can vary with the shell temps, based on design.
But yeah, they take a lot more surface area than a similar output iron/steel stove. The shell materials can affect that rate of transfer too. That's why you see a big difference in designs based on application/materials. And lots of heated benches/chairs, sleeping quarters. If you have stone on your property, it could probably be designed in and trade $ for sweat. But the type of stone is important as different stones have vastly different heat retention and transmission properties.

Thanks for the info. Unfortunately life got too busy to make the build you told me about. But I'll eventually get to one of the events.

Kosmik, I might go and see if I can help build that masonry heater over by your area - I'm not that far. I've also been thinking about signing up for the annual Masonry Heater Association's meeting in North Caroline at the end of April. I wish it was closer. Yes not all stones are alike - avoid sand stone because there are better ones. Also, concrete blocks from HD or Lowe's aren't too good.

But granite based stones are good. This masonry heater looks like it will last forever - outside made from chiseled granite rocks,


For some reason I really like the looks of round river rocks on a masonry heater. There's a rock quarry with a big pile of discard stone near me. It is chiseled pieces mostly. I'm almost a scared to ask them if I can have some of the discard. Scared they'll say go ahead and take as much as you want. I guess I could use the green marble tiles I already have somewhere else.

Before you know it I'll be building masonry heaters for a living!

 

[Kosmik]

If there's one thing we have in the Rocky Mountains, it's granite.

 

[byQ]

Today, I went out and picked up a load of rock from the discard pile at a rock company - it cost $20. There was silver-gray mostly and to a lesser degree silver grey with orange/rust. I tried to gather the greys with orange/rust. The pieces usually have one or more straight cut edges. And are about 2"-3" thick, and most pieces are bigger than 12".

So, these rocks should make an interesting outer shell on a masonry heater. They are dense and heavy. I'll make the outer shell 4" thick and backfill with mortar when I put a narrower rock in place. It will be fun arranging the rectangles, triangles, trapezoids, smalls, etc. into some sort of interesting pattern. I got about 4 large pieces that are 3' or 4' long and a foot and a half wide. I'm not a rock mason but I bet a guy could wack these long pieces with a sledge and use the resulting pieces like they were pieces from a jigsaw puzzle.

 

[DougA]

Don't forget that the outer shell has to be a self supporting wall. My feeling is that the 2" pieces are too thin and will not hold the weight of the ones above them when they are that large without wanting to buckle. I'm guessing you're going 8' or higher. Backfill with mortar is not that strong and the thin mortar will want to crumble and then you've got a real problem. I'd prefer to use 3 or 4" pieces. Just my thoughts and I'm not a mason but you may need a mortician.

 

[byQ]

Don't forget that the outer shell has to be a self supporting wall. My feeling is that the 2" pieces are too thin and will not hold the weight of the ones above them when they are that large without wanting to buckle. I'm guessing you're going 8' or higher. Backfill with mortar is not that strong and the thin mortar will want to crumble and then you've got a real problem. I'd prefer to use 3 or 4" pieces. Just my thoughts and I'm not a mason but you may need a mortician.

Ya, that's a good point. At first,I was thinking the same thing. I was trying to get some bigger pieces (got a few) but the 1"-2" were more plentiful and I kind of got sidetracked. Here is a picture comparing the thicknesses. I guess I could open the wallet and buy a pallet of 3 to 4 inchers and use those 1 to 2 inchers for a path or something. I'm going back tomorrow so I'll see what I can do. There are two 3"-4" slabs that are like 4' x 2.5' that I might try to figure out how to load. hmmm........

 

[DougA]

Take a sledge and break up the ones that are too heavy to load. If they're that heavy, you won't be able to work with them when you are on scaffolding 5' up. The other option is to use 2 thinner pieces mortared together. Not sure if I would recommend it ... but.

 

[byQ]

Take a sledge and break up the ones that are too heavy to load. If they're that heavy, you won't be able to work with them when you are on scaffolding 5' up. The other option is to use 2 thinner pieces mortared together. Not sure if I would recommend it ... but.

I think those large pieces are too solid - a sledge will just bounce off of them. I was thinking about them for a bench but I realize they are too thick, and ya too big to move around.

Here is How I can use the 2" thick field stone pieces. I will use what is called the facing method - build a brick inner wall first, have metal connectors stick out of the brick wall, and connect the field stone wall to the brick wall.
* First, build the core of the masonry heater and wrap it with fiberglass or cardboard. Measure it's size.

* Second, build the outside of the masonry heater on the floor (all 4 sides) - that is all the field stone will be loose/dry fitted together like a jigsaw puzzle on the floor. I'll bust down any real large pieces. So I've got a pattern (a completed puzzle) of the 4 sides laying on the floor.

* Next, build a wall around the core using common brick, but build this wall such that the bricks are mortared together not flat but on their sides. So instead of a 4" thick brick wall you get a 2.25" thick wall. As this wall is being built trace the pattern of the flagstone onto it with a marker. The ideal thickness for a masonry heater's outer shell is 4" to 5". So 2.25" (brick thickness) plus ~2" field stone thickness (plus a little mortar on both sides of brick) will put the outer wall in the 5" range.

* Place little metal connectors into the mortared joints of the brick wall. And place these little connectors in places where you can see that the joints of the field stone will be (remember you traced the pattern onto the brick).

* Now butter the backs of your 2" thick field stone and lay them into place. In addition, an anchored mesh could also be used between the brick and field stone walls. Hopefully, the metal connectors will line up with the joints between the pieces of field stone.

 

[DougA]

That would work but a lot of work. I'd aim for 4" width with mortar on one side of the brick only.
I did a flagstone patio like that. We had a cement patio and I laid out the 2 - 3" flagstone pieces and mortared them onto the cement. You should use high strength mortar and buttering the back of the stone fully is essential. You really have to press the stone against the brick to get all of the voids out. Not easy when it's vertical.

 

[Christopix]

I'm going to start watching this thread. Kinda interesting stuff these Masonry Heaters.

 

[DougA]

Don't forget that the thicker the stone/brick facing is, the more mass you have with heat stored in it. IOW, if you are burning 24/7, thicker walls are good, if not, better to go thinner. It's sort of like steel stove vs. cast iron vs soapstone. They all should give the same heat but if you want quick response for fast heat in the morning, steel is better.

Provided that the firebrick is done well (no leaks), I'd think about using the masonry heater without the stone facing for a month and see how that works. May be ugly but very functional. That way, if you want to alter anything, it's less work. Just a thought and something I may do. You may find thinner is better.

 

[Kosmik]

I'm going to start watching this thread. Kinda interesting stuff these Masonry Heaters.

Yeah. The more I read the more I like them. Especially when it comes to 'user friendly'. Only needing your attention a couple times a day is hard to beat without electricity.
Not to mention reduction in fire danger with all that stone liberally applied.
And with the versatility of the materials, the options with design and integration into the whole house are impressive.

Still, if it weren't for the inherent danger of running flue gases under your feet, I'd be going with a Roman hypocaust or Korean ondol.

 

[byQ]

Well, I went back out to the rock company's discard pile today (another $20). This time I was more focused. That is, I was looking for cut stones of a certain thickness and size. Last time I went, I was too distracted by the stone's appearance and got sidetracked on larger sized stones in the 1"-2" thickness range.

But this time, I was looking for stones in the 3"- 4" thickness range. I found some and most of them were between the size of 1 brick to 3 bricks (good size for stacking). They are a whitish orange color and dense. I don't know if I have enough of these orange stones so I grabbed some gray stones of the same thickness. And, I have some large orange stone in the 4" - 6" thickness range that I will try to use at the bottom (base) of the heater.

 

[DougA]

That looks a lot better.