Replies

1. 
   Piffin | Jun 23, 2002 05:05am | #1

   36" wide and 30" high is pretty standard hereabouts. A Rumsford would be taller though than it is wide with other features to reflect heat into the room such as angled sides and a small back. The larger you make the openning, the higher the chimneey should be to create draft, especially if this is an open screened room. You know how smoke can gutter around a campfire? a high chimney has more natural lift.

   Excellence is its own reward!
2. 
   JCarroll38 | Jun 23, 2002 07:24pm | #2

   Superior Clay (800-848-6166) offers manufactured fired clay components for building Rumsford-style fireplaces. These include dampers, pieces for the throat, and two-piece clay smoke chambers. They also offer a lot of solid information on the assembly of a Rumsford fireplace. Jim Buckley, who is a consultant to Superior, has written several articles about building Rumsford fireplaces, one of which appeared in the Journal of Light Construction in March, 1994. I love Rumsford fireplaces. And, since they don't have a sloping back wall, they are actually easier to build than traditional fireplaces.

   I have, however, built many traditional fireplaces that have been very satisfactory to my customers. If you choose to build a traditional fireplace (which has a bigger and deeper firebox), don't rely on guesswork and rules of thumb. A fireplace that doesn't draw is a sad thing. Get the proper dimensions and have them on hand when you lay out and build your fireplace. These are widely available; I still have a tattered U.S. Department of Agriculture bulletin (Farmer's Bulletin No. 1889) that I picked up for free in the 1970s. I've built numerous fireplaces following their recommended dimensions--all to the great satisfaction of my customers. These dimensions are printed in my book, Measuring, Marking & Layout, Richard Kreh's book, Advanced Masonry Skills, and many other publications. I can't tell you how many times I've heard people expound on the "art" of building a proper fireplace. In my opinion, there are no secrets involved; the trick is to get the mason to follow these widely available dimensions.

   Few of the chimneys that I've built (including those with traditional fireboxes and Rumsford-style fireboxes) have ever had a flue cap. This means that rainwater that falls on the open flue, goes down the chimney and is simply absorbed by the masonry mass in the smoke chamber. The fact that these fireboxes are partly or entirely inside the house, however, means that the moisture is regularly evaporated by fires and conditioned air. On a chimney built outside the conditioned space and used infrequently, I would be concerned about the build-up of water. In your situation, I recommend that you build the wash at the top of the chimney carefully, leave a few inches of flue projecting above the wash, then intall a screened flue cap. These keep water out of the flue and discourage critters from taking up residence in the chimney. They can also be removed when it comes time to have the chimney cleaned. If you can't get a flue cap locally, try Copperfield Chimney Supply 800-247-3305.

1. 
   RodBishop | Jun 23, 2002 08:14pm | #3

   You couldn't go wrong with a Rumford design. Just as square as they are tall. They can be built with a slanted back wall, though some will disagree wether or not this is a "true" Rumford. Who cares, as long as it works, and it will. A taller chimney is better for draft, no question. Here is one I built under an attatched gazebo. I know, Rumfords should not be built with a raised hearth, but it's what the homeowner wanted. Also, here's a link for a great book on Rumford design, all the measurements needed, etc. 

                                                                                           Rod

1. 
   JCarroll38 | Jun 24, 2002 05:54am | #4

   Rod,

   First of all, nice work! However, the idea that a Rumford fire place can be built with or without a sloped back wall does not square with what Count Rumford actually wrote. I've read Vrest Orton's book and I've read several articles written by Jim Buckley. I've also read Rumford's own writings on fireplace design. (These are in the Collected Works of Count Rumford, Vol. II, edited by Sanford Brown. Unfortunately, this book is out of print; I was able to get it through inter-library loan.) Having gone back to the original source, I can assure you that Vrest Orton was wrong about the sloped back and that what Jim Buckley has to say accurately reflects the work of Count Rumford. There is no mention of a sloped back in Rumsford's treatise on fireplaces and every description and drawing of his fireplace shows a straight back. If the original poster wants to learn about the fireplace Rumford actually designed, I would recommend that he check out what Jim Buckley has to say. Better yet, get a copy of the Collected Works of Count Rumford and get it straight from the horse's mouth.

   John Carroll 

1. 
   RodBishop | Jun 24, 2002 12:55pm | #5

   Well then how 'bout we call it a "modified" Rumford. I've built them both ways and they both work. I, myself, like the sloped back. It helps in positioning a smoke shelf, and it just plain looks good. I've known for years that a "true" Rumford is built with a straight back, however, in many years of building them both ways, I've only had one customer insist on having a straight back. Loosely, the earlier the house, the straighter the back. Thanks for your comments, John.

1. 
   JCarroll38 | Jun 24, 2002 04:48pm | #7

   Rod and Mike,

   I practiced what I preached and went back to the Count's writings last night. (I copied the entire treatise from the library book.) After doing that, I've found that I have to retreat slightly from the statement that Rumford does not mention a sloped back. Rumford does mention the use of a sloped back and suggests, in a footnote, that it increases the radiant heat thrown off by the fireplace. For Rumford, however, the main reason for the sloped back is that it provides space for building a fire. His treatise concentrates on the modification of existing fireplaces, with the goal of making them draw better and provide more heat. In smaller existing fireplaces, these modifications would cause the firebox to be too shallow. His remedy was to build a back that went straight up until it cleared the fire, slope gradually in, then resume a straight line just above the fire which then runs straight up to the throat. I've never seen a fireplace built like that!

   As I mentioned above, Rumford found these sloped-backed fireboxes to be very efficient. He wrote in the footnote: "Having been obliged to carry backward the fireplace in the manner here described, in order to accomodate it to a chimney whose walls in front were remarkably thin, I was surprised to find, upon lighting the fire, that it appeared to give out more heat into the room than any fireplace I had ever constructed...This opens a new and very interesting field for experiment, and bids fair to lead to important improvements in the construction of fireplaces."

   It seems to me, Rod, that the good Count would endorse your slightly sloped-backed fireplaces--as long as they drew well. His main concern was the size and configuration of the throat and the layout of the three walls of the firebox. I stand corrected. However, I will add that most of Rumford's treatise and five out of six of the drawings from side elevation show a straight back. Like you, I've built them both ways and I've gotten really positive feedback from my customers.

   I apologize for overstating my case in my prior post. I should have done my homework before I leapt into the discussion.

   Sincerely, John Carroll

2. 
   xMikeSmith | Jun 25, 2002 04:24am | #8

   I modified an old smoker in  a 1910 seaside mansion back in the '70's... followed Rumford's designs for modifying to a T... solved that problem and got a lot of work from the owner over the years.. as she swore I was a gen-i-us.. course I gave full credit to the count.. but she didn't care..

    I' ve built  several others to the rumford designs and to the USDA measurements .. all successful..got to agree, if you stick to the tried and true dimensions it's hard to go wrong.. unless you screw up the smoke shelf in the traditional designs..

   two years ago we did one of the Superior Clay Rumfords and everyone from the mason to the building inspector to the owners was suitably impressedMike Smith   Rhode Island : Design / Build / Repair / Restore

3. 
   MikeR | Jun 24, 2002 02:45pm | #6

   Agreed...Superior Clay is the way to go.  Just make sure you order exactly what you need as those Rumford throat pie-shaped pieces aren't cheap.  And be ready for some lifting if you build an opening that large as the required flue liners will be quite heavy.  I end up using the 18" x 20" I believe and they're 141# each!  The 13 or 14 of them I had to lift into place were not fun!

   My fireplace was the first I ever built as I work in Florida and I don't get many calls for them.  I followed the designs on the Superior Clay web site and assorted links and our Rumford works very well.  Beautiful draw, no back smoke, etc.

   I did mesh cap ours to keep brids and other animals out and also ran a ground strap down its length as a lightning deterent. 

   Now that will bring up a whole other discussion on lightning rods!

   Mike