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Sampsa Kiuru decided to install a Finnish masonry heater in his national eco design award winning home in New Zealand. Four features set Sampsa’s heater apart from other heaters that we commonly build, although all of our masonry heaters by Maine Wood Heat tend to be special and custom made.

First, he chose for his heater a large beautiful cast iron air tight door with a panorama bay window shape. He also chose to have us design a current state of the art prototype hand built firebox to introduce over draft air in twenty-four separate air ports. In addition, he chose to add to his heater design a little known cast iron needle bed heat exchanger system from Finland that picks up super heated hot air off the top of the heater and sends it out by fan to a box beyond the heater where the hot air heat is converted to hot water heat and then pumped to remote areas of the house. And finally, Sampsa had heard about some soapstone mined in Finland and he wanted to try to get some to use in his heater. This needle bed heat exchanger will be discussed in an upcoming blog.

The last three items I will discuss separately in future blogs. But today I want to talk about the door. The door was hinged on the right and opened from the left and springs on the hinges allowed it to swing back to the nearly closed position after it was opened for loading wood. For safety reasons the handle was removable. A single pane of beautifully molded ceramic glass covered the three facets of the door. Air wash draft controls allowed air to wash up and down the face of the door.

Unfortunately, most masonry is made out of rectangular modules. A panorama door creates a special challenge, not simply because of its bay window shape, but because there is no easy way to step out self supported brick modules over the top of the door. The door of a heater is gasketed and while secured with tap con screws or other means, is not supporting any of the masonry above it. If it did, it would push on the masonry and crack it when the fire heated up the mass.

This means that the bay window shape of masonry above the door that spans the door has to be supported another way. Reviewing many photos of heaters built by others with panorama doors, we noted that many of them were made with soapstone blocks where stones above a fire door can be laterally connected to stones on the left and right with pins and clips allowing them in some sense to hang in mid air over the door without sitting on the door frame itself.

In brickwork for our five sided and six sided heaters that we have built, we have the two 135 degree angles to either side of the loading door and we typically carry the faceted shape all the way to the top of the heater. In addition, we typically mount a one plane door on just the front facet of these heaters and are not using a door that wraps, in a sense, around three facets of masonry. You can see a good example of this in the photo on the left of the Belanger masonry heater we built a decade or more ago.

These doors are mounted on a flat front facet. We, none the less have to bridge across the lintel opening, so we have done this two ways. One is to make a three piece welded angle iron which follows the shape of the three front facets and which spans the door opening from the back face of the veneer and turns left and right beyond the door opening to follow the two 135 degree angle facets of the brickwork. The angle iron has to be welded very accurately and at the ends of the angle iron we always lay down a strip of l/4 inch mineral wool to leave the metal some room to expand (as the metal is potentially moving in two directions because of the welded shape).

We also put down a strip of high temp ribbon gasket on the special faceted angle iron lintel and lay the bricks dry on the angle iron. We have had fairly good success with this approach but do not like it as much as our second option which is to span the door opening with a “jack arch” where the spring stone for each side of the arch actually starts on each side facet beyond the opening and then picks up the lateral thrust of the arch right at the corners of the front facet where the jack arch begins, which you can see in the above photo. The spring stone we typically make out of soapstone, which is easy to work with a 135 degree polished angle on it to match the angled brick we are using above and below it. We step the back half of the soapstone spring stone so that the brick coursing of two courses works perfectly into it. Once the arch is laid and the form removed, this approach gives us a reliable flat arch lintel over the door with no odd shaped metal angle iron to depend upon. You can also see such an arch in the photo of the Belanger heater above.

With a panorama door the front facet we are working with is only about l6.5 inches wide and typically, the facet does not go all the way up the face of the heater so we are essentially stuck with making something that follows the door shape in the brickwork below and above the door, but not necessarily all the way up the heater and including the oven door. In Sampsa’s case we wanted to not make an angle steel lintel on such a short facet and run the risk of the lintel causing cracking problems even if we gasketed it thoroughly. Furthermore, the oven door that Sampsa chose, he and we wanted to mount on a flat facet all the way across the front of the heater. So we basically needed to design the bay window facet for the first third or so of the heater and then switch back to a flat face on the upper half. We were extremely fortunate to have a gifted woodcarver and house builder in our group who was there with me for three days before the hands-on workshop began. Together, Chris Naylor and Albie designed a brick layout and did all the cuts to create the bay window layout below the door and then also designed and built a form to create two custom made faceted bay window castable refractory lintels to span the door opening without resting on the door itself. Albie cut all the brick shapes on a rented diamond wet saw (a ten day rental fee was half the cost of a new saw…we almost bought a saw to have it for future projects). Chris made up a plywood template to make sure that each course below the door matched the previous course and Albie cut out the majority of bricks and laid them up dry, course by course, all numbered on work area planks on scaffolding in front of the heater.

Chris went to work measuring and designing and made two beautiful one off forms to create both an inner and an outer course castable refractory set of lintels. Sampsa called the refractory supplier and at my request had some special high temp super strength castable added to our order along with some fine stainless steel needles, so that if cracking developed in the span of the lintel of the door, we would be able to maintain its integrity with the needles. The refractory supplier was a local plant an hour or two away that used products made by Shinagawa. One order of firebrick and other refractory materials arrived but the balance was still missing so we made a special effort to get this second batch of special firebrick splits and refractory concrete and needles all sent on a second order in time for the workshop.

Sampsa wanted his heater to have a stucco finish with possible soapstone trim. With all the curved shapes in the clay stucco around the beautiful window openings, Albie suggested that the front corners of the heater also be rounded so we shaped all the corner brick with locally purchased chisels and hammers and trimmed the corners with a special “Scutch” hammer with a row of galvanized teeth for chipping on its business end. With a planned stucco finish, we knew that we could make a veneer lintel out of the high temp white castable since it would be covered by stucco when that stage of the finish work in the house and the heater was done.

Once the workshop folks started arriving, we poured the two castable lintels. The first was the shape of the inside of the panorama door and was the thickness of the local brick, about 4.5 inches deep. The ends of the shaped lintel were long enough to anchor back into the flat face of the heater. Higher courses would anchor it and keep it from tipping forward and down. The inner or core lintel followed the shape of the outer lintel on its front face and brought the line flat on its back face back to the rectangular core plane that would continue on up to the oven from that point on.  When the castable was poured in the oiled wooden forms the white high temperature castable got so hot that it started to send vapor and odors into the air from the oil finish on the wood (when we later designed and poured an oven lintel set of elements, we decided to pour these elements outside.) While the two piece lintel plan with needles embedded solved the bridging problem, the expansion joint between the two lintels was forward of the eventual front plane of the upper portion of the heater and would show, so we designed and cast a third lintel to cover the two bottom lintels and rest only on the outer lintel to seal off the joint between them but put weight only on the veneer materials, not the core materials. On top of this course we then designed and shaped an oven shelf made out of soapstone which I will discuss in a special Sampsa’s Soapstone blog soon.

Once the bay window base courses were in place, we custom cut the door framing brick courses in a similar fashion but with an opening for the door frame in our dry stack layout.  As Sean and Ian laid up the brickwork, every course was checked with the plywood template (that Chris had made to help create the forms) to check the accuracy of the dry cut brick layout. Once the doorframe brick with the lintels and the soapstone shelf was in place we continued with additional work to anchor the lintels. The door mounting came at a late stage but I will continue with the focus on the door now. The door came with beautiful cast iron “t” shaped anchors that mount on the inside corners of whatever veneer you are working with. All of the Future door series come with this anchoring feature and a braided high temp gasket on the inner face of the doorframe. As you tighten the corner clamps the gasket seals off the whole inner face of the door against the veneer or the core face depending on which face it is mounted. In our case the veneer was a standard 4.5 inch thick New Zealand brick but the bolts supplied with the doors were not long enough. Chris went to the store and bought a length of metric threaded rod the same diameter as the bolts and also bought eight couplings for the rod and bolts (four for the big door and four for the oven door). Sven worked on creating additional lengths with couplings for each door “t” bracket. Each length of rod had to be filed down to make the threads connect properly and this Sven did with one magic tool or another as part of his array of blades on his very elegant Swiss Army knife.

When he pulled out a very functional pliers blade, I was completely won over by his knife. Not happy with just creating extensions for the bolts, Sven went on to cut pipe into short sleeve sections to go over the exposed couplings and galvanized threaded rod and then painted the sleeves with high temp black paint so that the attaching system inside the four corners of the doors looked intentional and elegant. Knowing that we were also going to stucco the outside of the heater eventually so that no red brick would be seen, Sven also went on with small Japanese stucco trowels and put a layer of refractory mortar on the exposed common brick faces inside the door opening. When we went to mount the loading door we noted that we were not quite centered on the heater, so we removed the loading door and trimmed back the left facet of common bricks (soon to be covered with refractory mortar) with a diamond grinder and reset the door in a stable and centered position.

We also mounted it about 10 mm proud of the brick veneer to allow for two layers of stucco to be added later that would build out to the doorframe depth. We had to do this in fact for every clean out door as well as the ash box door. When we were all done with all the door mounts, every door had little shims in place temporarily to hold them out to the proper stucco (to be added later) depth. Once the doors had set up a little, we pulled the shims and carefully put mortar in behind each doorframe to fill up the hidden gap there. We used very narrow pointing trowels for this job.

When we were all done the panorama door was installed and gorgeous, even without any stucco added. Although the door was a technical challenge to mount in the brickwork, we were very happy with our results and were glad that Sampsa had chosen it.

Sometimes, the best teaching happens around a whole group solving problems that the leader has not run into before. In such a circumstance, everyone gets to think and scheme and invent rather than just learning someone else’s system by rote. As I explained early in the course, I have deep experience with one facet of masonry heater design and that there are other traditions of masonry heater design and construction that are also valid that can be pursued. I do not know the Austrian design and calculations system but my son Scott has just taken a weeklong course on this subject with Rod Zander and Tim Seaton in the U.S. and he can now add this knowledge to his own design process when he is challenged to come up with a custom heater for someone. I also mentioned different design traditions from Russia that several people are experimenting with in North America. The idea is to create something that burns cleanly and efficiently and is beautiful that is made out of masonry so that it can store a great deal of heat and radiate it into the room over a half day or longer. In the Finnish heater tradition within which I work, there are still changes and improvements going on. We now make a better Albie core system than we did a few years ago and we are constantly scheming ways to improve on our designs.

The next blog will discuss in detail the design and construction process we used to give Sampsa a custom made firebox with a great deal of over draft area distributed from beneath the firebox and up through the side walls and into the heater through twenty-four one inch ports. We have done such designs in Scott’s little soapstone masonry heater on our Web site and for two clients in the field in 2009 who are reporting good results.

Firebox core elements from Austria feature these over fire air ports and a new cassette designed by our friend Heikki Hyytiainen from Finland, also features this over fire air port air supply. We will be testing Heikki’s new world patented cassette soon in the States and will have a unit at this year’s Wildacres event in Little Switzerland, North Carolina with the Masonry Heater Association. Heikki will be present to build a heater with his high efficiency firebox cassette in it and then I will take the unit home and integrate it into a permanent heater somewhere near home. Far away from home in New Zealand, we had no cassettes or Austrian modular firebox systems. Everything we did, except for the hardware, we designed and built from scratch to maximize the learning curve and to avoid huge shipping fees. This made the course much more technically challenging than normal and much more gratifying ultimately in the end.

Look for the firebox design blog next.

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Maine Wood Heat