Firebox
I tried to get a mason to lay the firebox for me. I called all around and most weren't interested. There was only one man who was and after 1 missed appointment, he showed up to check it out. This mason does quality work, and I was sure that he could do the job. He wanted $1200 to build the firebox for labor only. I would supply materials, the fire brick, refractory mortar, and damper.
He was supposed to show on Thursday. By Saturday I was preparing the fireplace slab myself. The form was built. I cut the re-bar and planned and installed the outside air ductwork as shown below.
The re-bar supports the front of the slab by cantilever from the foundation.
On Sunday I poured the base. I had lost hope that the mason was going to show and was resigned to doing it myself. Earlier in the week, I had ordered 2 books on fireplaces, one was specifically on the Rumford fireplaces, called The Forgotten Art of Building a Fireplace, and the other was a textbook on good masonry principles.
I laid out the firebrick in the pattern of the fire box. But there was no mason to build it.
I needed a plan B.
While researching on the internet, I came across a site http://www.rumford.com
To make a long story short, this engineer in Britain studied fireplaces and came up with a set of recommended dimensions. The important part was the throat and smoke chamber above the firebox. This appealed to me for a few reasons. One was that the firebox walls were straight, all of the curved parts, the throat and smoke chamber, were cast pieces. Thus, it was easier to build. Second, the dimensions were shown in drawings. With the traditional design that the mason was going to build, the walls had to be sloped. Without the experience of a mason I had no way of knowing what the optimum was. I also had an offset from the firebox to the flue.
I cut out a vertical elevation model from a piece of cardboard. Comparing this to the space that I had, I thought that it was practical do install the Rumford. I did a little more sculpting on the inside to fit it.
Another trip to Atlantic Building Supply got me the Rumford throat, damper, and smoke chamber. Asen, the mason that helped me out with the rest of the house offered to help me with the fireplace even though he never built one before. The two of us started it on Sunday April 8th, and laid the bottom and first 3 courses of firebrick. Asen left and that night, I bricked the sides. The next morning I mixed cement and filled the void up to the level of the brick, and so it went for 4 cycles until we laid the last course of firebrick. The following day I placed the throat on the firebox, and the size was not right. The throat opening was 2 1/2 inches smaller than the firebox floor, front to back. I had thought that I had followed directions, but yet it was wrong. I went back to the website to review the instructions to see if I missed anything. It seems that I had. They mentioned that in some cases it might be necessary to slope the top 3 courses of the fireback forward. I had to rip out the last 2 1/2 courses that I completed the night before. The bricks needed to be cut to slope the back inward unlike the image below. The size that we were building , 30 inches wide, was considered small. The throat design was changed a little and not shown on the drawings. I continued on to set the throat, damper and smoke chamber where I had to hold for an inspection.
I went down to the building department to schedule an inspection and found out that I needed to pull a permit first. The chimney and fireplace work was not planned.
Rumford Fireplace
These components were produced by Superior Clay and sold by Atlantic Building materials in Chatham.
This is the 180 firebrick that was needed to build the first firebox design. The Rumford took half as many.
I had help from Asen laying the firebox. He used a structural pattern interlocking the corners laid as strechers instead of the traditional way fire brick are laid as shiners. I cut the corner angles with a diamond blade chop saw.
After he laid the firebox, I would take over and brick up the sides and then fill in with concrete.
The fireback needed to be sloped forward a little. This came as a surprise. I cut the bricks in an angle with a diamond blade chop saw.
My brother Matt helped mix concrete one day.
The Rumford throat was set in place