Monday, April 16, 2007

Building a Rumford Fireplace - Part I

Rumford fireplaces are differentiated from typical American fireplaces by their tall/shallow fireboxes, their streamlined throats, and most importantly... by their promise of actually producing more heat than they waste! They are designed to maximize the direct and reflected radiant heat from the fire in your fireplace. For everything you ever wanted to know about Rumford fireplaces, see http://www.rumford.com. For one person's experience, building a Rumford style fireplace in a timber frame home, keep reading,and stay tuned!

Having a genuine desire to build my own functional fireplace, but possesing no real knowledge of proper fireplace proportion and design, I decided to buy a 48" kit from Superior Clay Corporation. In exchange for my money, they shipped to me: a lot of firebrick, a refractory throat, a two piece clay smoke chamber, a cast iron damper, clay flue liners, refractory mortar, and instructions for building my own fireplace. (One could also buy prebuilt firebrick walls from this company, but I decided to lay-up my own, based on their straightforward instructions.) Everything arrived promptly and in perfect condition. Most of the "magic" for getting the proportions (and draft) correct seems to be in the design of the throat (pictured at right).

Step 1. Laying the firebrick hearth. After reading the directions, drawing dimensions on my slab, dry-laying some bricks without mortar, and checking the dimensions of my unmortared hearth with the dimensions of throat, I was ready to mix mortar and put the hearth together. This step was fairly easy. I mixed the mortar fairly wet (looked like cake icing), buttered the bricks, and squeezed them into place one at a time such that the joints were 1/16th to 1/8th of an inch apart. This particular refractory mortar "sticks" the bricks together within a few seconds, but takes a long time to dry. At a few points I was unsatisfied with my work, so I pulled the offending bricks back up, scraped off the mortar, applied new mortar and placed those particular bricks again. No pressure to hurry. In fact, the mortar was easy to wipe off - even an hour later, so it was OK to be sloppy as well.

Step 2. Laying the firebrick for the sides of the firebox. The back of the Rumford style firebox has a flat side and two angled sides. At first I thought I should weave the brick courses of the three sides together for strength. But then I realized that the kit (no matter which size you buy) is thoughtfully designed to use exact full-brick and half-brick increments. I also realized that in order to weave the bricks together, some would have to be cut on a 45 degree angle, which would leave a thin sliver of brick that might be more prone to breaking or spalling. The full-brick-halfbrick design suggested in the instructions is about the best you can do, aesthetically, without going to something like a herringbone pattern. Ultimately, it seems that these firebricks are more of a "liner" than a structural element of the Rumford fireplace kit, so I have no qualms about laying up the three sides of the firebox seperately. The trick to laying these bricks seemed to be... keeping the courses level, keeping the courses straight, and keeping the joints a consistent thickness.

Step 3. Laying up the structural backing. Here's where I've decided to deviate from the instructions - slightly. Although not specifically mentioned in the printed instructions, the web site for the rumford kits suggests that you might want to pour your fireplace structure, rather than lay it with block. This is the route I have chosen. Of course, concrete at anything over a few inches thick, has some incredible force pushing outward while it is in liquid form. I have decided to pour no higher than 2 feet at a time, and I will "kick-off" or otherwise support this brickwork when I pour against it. The web site also advises to make provisions for a bond-break (or even better - an expansion gap) bewtween the firebrick and the poured cement backing, if you chose to pour cement. More on that when I get to it. For the conventional block fireplace route, see the instructions on their web site.

Here you are looking at the only brick I have ever laid in my life. I'm proud of it so far! 5 courses of brick (laid on edge - these are called "shiners") equates to about 2 feet of height. The fire box will eventually be 10 courses high - or nearly 4 feet tall, before the throat is mortared on top. In the bottom of the hearth, you can see I have left one brick out (and a hole beneath the hearth) to serve double duty as a "fresh-air make up" / "ash dump." Perhaps I will make or order a trap door set-up for this hole. In the mean time, a loose brick will serve the prupose.

In the left of the last picture (and in the right of the second-to-last picture), you can see a partial 36" bread oven kit - from the same manufacturer. The bread oven kit (aka wood fired pizza oven) is just sitting there now so that I know it will fit when I bring the entire masonry structure up to about 4 feet and start incorporating it with the fireplace. I'm more excited about the bread oven than I am the fireplace (my wife's a great cook!), so I'll be sure to document its construction as well.

3 Comments:

Blogger craig said...

how did the rumford fireplace and oven turn out. Believe it or not, I will be building the exact fireplace and oven in the spring for a client of mine. Never done one before. I would be interested to see photos of the finished product and here any suggestions or tips that were not included in the instructions that would make my first Rumford a success. thanks, Craig

dinostar@mac.com
www.brixstonemasonry.com

December 8, 2007 at 12:30 AM  
Anonymous Buckley said...

I just ran across your blog and would like to know how the Rumford turned out. I did find your April, 2008 comments about the oven. I'd be interested in learning more about your experience.

Jim Buckley
Buckley Rumford Co.
www.rumford.com

July 19, 2008 at 12:36 AM  
Blogger oldmilwaukee said...

Jim,

Put me in the happy customer category. The Rumford works great. We've only built 3 fires in it, as summer happened upon us too soon. It draws like crazy. You were right about the pizza oven flue liners - plenty big enough, as it draws great too. I think we could have gotten away with smaller flue liners on the Rumford. As it is, I would like to modify the damper so that I could throttle the amount of air being draw up the chimney. The cast iron flue damper I bought with the kit is "all or nothing" if I understand it correctly. It simply draws too well, but that's a nice problem to have I suppose.

Some day (this fall/winter?!) I'll write more about the Rumford. From our brief operational experience with it - we are very pleased.

The pizza oven has developed a few more hairline cracks. New ones, so they are not likely due to a broach of the break-in period protocol. They don't concern me too much - I mean I dry-laid the whole fireplace surround so cracks should not concern me. I just wonder if other customers have experienced tiny cracks.

I'd be glad to send you more pictures of the Rumford or the pizza oven if they would help your web site and promotion of the kits. Just let me know.

July 19, 2008 at 4:37 PM  

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