Buckley Rumford Fireplaces
Pershern Broken Throat

From: "Andy Pershern"
To: buckley@rumford.com
Subject: A 48"Rumford in CDA, Idaho, and 24" Bake oven
Date: Thu, Feb 24, 2011

Hi Jim,

Unfortunately, 2 nites ago, the curved throat of our 48” dropped down into the fireplace. Im researching a fix, possibly with INSUL-Stick 2000 degree repair mortar. Im going into Coeur d’ Alene, next to see Silver Lake Masonry where I got the Rumford originally. They can get Insul – Stick. To replace the throat, the whole front of the fireplace would have to be removed. Do you have any Ideas? I’ll send a few more Pics.

Andy Pershern
208 755-1797 cell


    Jim Buckley
    with copy to Superior Clay


    I'm sorry to hear that, Andy. We have only known of one other one-piece throat that broke and dropped out in twenty years. See http://www.rumford.com/brokenthroat.html

    From the pictures, your broken throat appears to be similar to that one in that you've had some hot fires and the throat appears not to have been grouted in solidly. Grouting the throat in solidly, we think, not only makes it less likely to break or fall out but it also makes it less likely that products of combustion - heat smoke and creosote - get up above the throat into areas which may be close to combustibles. The throat is made with an exotic clay that does not expand with heat but still many masons might try to maintain an airspace around it like they are used to doing with metal dampers. We recommend solid construction, at least on the curved part. See http://www.rumford.com/instd.html

    But how to repair? Relaying the arch would seem to be a lot of work. Like you, I think I would try to cast a new throat but I wouldn't use Insulstick which is a mortar rather than a castable refractory concrete. Better to use Heat Cast-40 as described at http://www.rumford.com/store/refractorymortar.html

    I would clean off the area above the throat as well as you can and maybe install some anchors like bolts or rods to be cast into the castable and secure the new throat to the surrounding masonry. Then make a curved form out of sheet metal supported by a couple of pieces of plywood cut into curves like bulkheads in a boat or airplane and load in the Heat Cast-40 with a hawk and trowel from the top. Bang, jiggle and vibrate the pour so as to make sure it fills the void and connects with your anchors.

    If your form and resultant cast throat are not perfect as would be difficult with your arched opening, you could fill out, parge, plaster and improve the shape by coating the casting with refractory mortar. This would be a good application for the Insulstick - or regular HeatStop 50.

    Meanwhile I will copy this to Superior Clay to see if they have any other ideas.

    Again, I'm really sorry this happened to you. I've enjoyed your page at http://www.rumford.com/Pershern.html where you taught me how to grill steaks in the oven. Let us know how we can help,

    Jim Buckley

    Ps: I have reattached your pictures so they can see them at Superior Clay.

Hi Jim,

Thanks for the response, it's 0 degrees here this am, and I have fired up the bake oven for a little added heat in the house. This fireplace has run hard every year since we built the house. It burns every day from mid to late Oct to early or mid may typically. It is and has been a GREAT fireplace and contributes a huge amount of heat for the house. We burn tee pee style with wood standing up as in the Pics we sent you. It provides a very radiant heat back out to the stone slate floor in front of the FP. The loop of radiant heat in front of the Rumford, runs hotter on the return line when it's burning, than the boiler sends it out! So it contributes back to the radiant system also.

The throat was grouted fully "behind" it, and down to the bottom of the front with an apparent form line vertical up into the rock and mortar however as shown in the new pics, there is a small cavity in "front" of it that the mason should likely have filled in also. This may or may not have provided enough support to keep it from falling in or getting even loose.

Forming and pouring in that location and tightness may well be close to impossible. I have worked on dams and other water resource projects and have grouted, parged, patched, poured more tight intricate concrete than you can imagine, this seems that a hand placed and packed, then screeded to shave and shape is the correct way to do this. I know I can do that. A question I have, If placing anything back in, is a construction joint advised to allow "some" relief of expansion or contraction and prevent future breakout?

Also, I fully intend on filling the void between where the point of the throat was and the cast grout is now, and fill to the front behind the masonry stone and back to that point.

The bake oven needs a bit of work where the flue goes up transition to the lid of the entry I'll do this now also, when I get the final plan / ideas to fix the Fireplace. The bake oven continues to be an incredible cooking facility, we have had some incredible dinners from it. The last one was DEC 30th, 30 PEOPLE! We did 30 steaks, 8 huge onions a ton of baby sweet peppers on long armed skewers, Black tiger prawn /shrimp too. It continues to amaze all who come for dinner, it's sort of a "cave man" meal. But all who are skeptical before eating fully change their minds after tasting the fire grilled delectables!

I will review the attached info you sent in more detail and get back to you with my thoughts.

Thanks again.

Andy Pershern>

    Friday, February 25, 2011
    To: Andy Pershern
    Cc: Superior Clay; Jeannie Rosanelli
    Subject: Re: Idaho featured Fireplace & Bake oven on website


    With your experience in grouting, pouring, patching and packing concrete, I am inclined to go with your judgment and preferred method. I'm sure you could lay up, pack in or plaster many layers of refractory mortar to build up a new throat. If you did that, your choice of InsulStick would be correct. I think casting the basic shape with HeatCast 40 would save time and "mud in your mouth" compared with maybe ten layers of InsulStick to fill out an 8" or 10" thick throat.

    I also can't judge from the pictures if the new throat, built up or cast, would be wedged in or if you would have to affix some anchors. I suppose, if you can get the first layer of Insulstick to stick, the finished layered throat would be monolithic enough and be supported on the firebrick so it would stay in place.

    I would pack whatever refractory material you use in solidly. Refractory materials do not expand much, if any, when heated which is why they can withstand thermal shock compared with materials that do expand and create internal stresses sufficient to make them fail.

    Keep me posted. If you want to buy your HeatStop Insulstick or HeatCast 40 from us we will sell it to you at our cost - about 30% or 40% below the retail prices listed at http://www.rumford.com/store/refractorymortar.html


Feb 25, 2011
Hi Jim,

The only depth to actually replace is the curved part of the throat that dropped out, which is the thickness of the throat itself. AS IT WAS, - fully backed with mortar in place, So a buildup of @ 1 ¼” to 2.5” would be the “replacement” of the actual liner that fell out. Then, -- at the front face where the bottom front lip of the 1 piece unit was, I plan on filling the gap there, horizontally @ 4 to 6 inches and 3 to 7 inches approx vertical depth, to the back of the rock facing of the arch on the fireplace. I could, if deemed needed, even, get a angle or ¼” strap and weld it under the present steel front frame, have it Rolled to the radius, weld it on, use some “mud Lugs” on the inside for the new mortar to surround and anchor to also. I could clean the separation existing surface of the original liner and the cast in mortar fill in place, no problem, tough spot yes, but do – able.

So Insul- Stick seems that it may be the most appropriate product in this application, is that your opinion also? I could roughen the existing surface, pin and lay a ¼” screen galvanized mesh over the Cast face, and then hand pack and shape/ screed to the profile as close to original. What would be the minimum depth I should replace with Mortar?

Insul Stick appears to be the most “sticky” of the products --- is that your opinion also?

Only the "front" curved face came out, the back and sides are solid and hard in place yet.

I also need to fix/ re point the vertical joint in some spots between the fire brick to stone facing , and sections on the angle intersections of the firebrick too, the fire brick is loose in a few spots. I can do this with Insul stick also likely.

Let me know what you think of this approach. Then I will calculate material qty’s and would be glad to get the materials at a break in price from you, As the dealer here, Silver Lake Masonry has none in stock and has to come from the east coast.

Thanks for the additional input, and offer at discount costs for materials, it is appreciated.

Andy Pershern


    I think your plan is just right. From your first batch of pictures I thought the throat was not grouted in from the top and you would have to fill a fairly vacuous space 8" to 12" deep. If you just have to parge, pack or plaster on a lining up to an inch or two thick, then I think you can do that with the Insulstick. Any mortar shrinks a little compared with concrete so I would build up your throat lining in two or three layers.

    I am still not envisioning the gap between the throat and the back of the stone arch but I would fill it solid.

    So, your throat was grouted in solid and our theory is that it failed because it wasn't grouted in solid. Why do you think it failed? Do you think the gap at the front could have been a factor? How about the steel front frame? Do you think it could have expanded and caused the cracking or weakened the throat? It would be nice to know why the throat failed so that we can not do that again.

    Jim Buckley

Andy Pershern to Jim

I don’t think the metal had anything to do with it, too far away. I personally feel the mason should have filled the entire area as I am planning to do. It’s a logical move to me, as Ive done a few fireplaces years ago. But my other grouting and concrete experience tells me that if that void was full, the heat transfer would have been much more even and spread out Im sure. So over time------------ it may have loosened the bond at the front lip, gradually working it’s way between the Grout and the Throat.

Other than that I don’t know why it failed. AS my other email stated, we have burned this hot for years, It’s meant to burn pretty hot, it’s a GREAT Fireplace! I wish I had it burnin’ right now! It’s the coldest we’ve been this winter right now!

I will look close at the cracked joint for signs of "time" in being cracked.

By The way, I will be out in Port Ludlow next week most of the week and poss the next. Im going to hep a buddy on MAtts MAtts bay, with some stone / slate work. Maybe I could pick up the rx supplies while there and meet you. I would be delighted to actually meet you!

Thanks so much for all your input and questions and ideas so far.



    How is the fireplace throat repair going? I'm out of town again - in Salt Lake City this time - but don't remember us sending you any InsulStick. Did you make it out to Matts Matts Bay?

    Warm regards,
    Jim Buckley

Pershern Rumford & Oven
Buckley Rumford Fireplaces
Copyright 1995 - 2011 Jim Buckley
All rights reserved.