Masonry Heater design and build in Australia

Hi Team

I have been planning to install a masonry heater for some time but I can’t just go out and buy a core here in Australia. I have been guided by Ken Matesz’s book on Masonry Heaters, "The Missouri Designed Masonry Stove and some of the draft plans I have seen at Firespeaking. I’m a residential builder so no issues with the structural side of the house (although I will need to get engineering before it goes to the local Council for approval).

Due to the cost of shipping refractory and cast iron materials from the US so my plan is to use local firebricks for as much of the internals as I can and cast some specialist pieces as required. The home is on piers and we have reasonabel access so my intent is to draw air from under the dwelling into the area beside where the ash tray and door are situated. Then come across and and up through the grates into the firebox. I intend to uses two 100mm (4 inch) sewer pipes with an operable gate to provide the required airflow.

My biggest concern is making the heat exchangers using 50mm firebricks on edge. I have planned on a 100mm (4 inch) opening to allow me to tie it in. Has anyone done this? Is it better to make some molds and cast them?

I have based my design on a 16 inch firebox using the PR04 door.

Anyway - the draft plans and spec are attached. Any feedback advice and recommendations would be greatly appreciated.

20230301 Masonry Heater.CAD.pdf (64.6 KB)

Cheers n Beers

@Jolls, Thank you very much for contributing your project drawings to the forum.

What is your timeline? I would like to respond with some redlining on your drawings but it may take some time.

Your comments and questions pretty much “hit the nail on the head”…

This is exactly the premise of a “hybrid” approach: leveraging the commodity unit of a firebrick while casting the most complex parts for strength and to minimize cutting and on-site installation time. From a design standpoint, casting components including the heat exchangers means that you can isolate the combustion part of the core from the heat exchange portion. Two great benefits this provides is the opportunity to insert an expansion joint (using 1/2" ceramic wool or 1/2" gasket rope) inside the core and it makes changes in configurations possible without changing the basic bond of the firebrick in the combustion portion of the core. I have learned that this modularity is important for efficient and versatile design development.

This is a valid concern. I assume the 50mm firebricks on edge you refer to is what we would call Firebrick Splits laid as shiners (on edge). Given the strength of the commercial refractory mortars (with sodium silicate in them) and the fact that the 5-run design has a built-in internal buttress in its channel divider, it is possible and definitely has been done. In fact, it has been fairly common in North America to lay the Contraflow heat exchange pattern which does not have the additional internal divider with Firebrick Splits. @mheat has been one of the long-time proponents of this approach and may have further comment. It is tempting to want to bond the heat exchangers into the combustion portion of the core for strength but my current opinion is that this opportunity for an internal expansion joint is very positive for a successful facing strategy, especially if considering plaster.

I recommend considering using exactly half of a firebrick unit as the width of your heat exchange channel to maximize material and minimize cutting. If a standard metric firebrick is 229 mm, you might work with 115 mm or 11.5 cm as your unit to account for some loss in length when cutting, some gain from the mortar joint and having a relatively round number.

I have shared some thoughts about foundations here:

Your questions about outside air warrant a reply unto themselves for another session or by another contributor.

This is a great door and exciting new addition to our catalog. I look forward to seeing your project come to fruition.


Hi Max

I didn’t see this reply before I responded to your other response. You have answered most of my questions in detail here. Thanks. I will provide your recommendations on the foundation details to our structural engineer so that we can get it through our local council. I have provided the drawing to Council, unofficially, as they are trying to determine how they certify the design of the heater given there are no directly applicable Australian Standards. It will take some time but I have a few months as we are at the start of Autumn (Fall) and we don’t intend to commence the build until Spring.

Cheers n Beers