Building a Masonry Firebox with Refractory Mortar Kalamazoo MI

Many fireplace masons in Kalamazoo are not familiar with refractory mortar, or they confuse the product with fireclay mortar. Masonry fireboxes are often laid in ordinary portland cement mortar, sometimes with a little extra cement or some fireclay added to make the mixture 'fireclay mortar'.

Leidal And Heart Mason Contractors
(734) 622-8485
101 E Keech
Ann Arbor, MI
 
Bashore Marco Masonry Inc
(517) 393-9704
6237 Aurelius Rd
Lansing, MI
 
Paul Henes Masonry
(734) 769-0880
3687 Jackson Rd
Ann Arbor, MI
 
TheBrickMasters.com
(586) 246-7848
137 Miller St.
Mount Clemens, MI
 
Giannola Masonry Co
(586) 792-2070
35086 Cordelia St
Clinton Township, MI
 
A Ct
(586) 772-1660
25530 SchoenheRR Rd
Warren, MI
 
Bornor Restoration Inc
(517) 482-1625
525 Filley St
Lansing, MI
 
Quadratic Masonry Llc
(734) 663-9646
3877 Albert Dr
Ann Arbor, MI
 
Hane Tile & Plastering Mason
(734) 971-8298
2771 Lookout Cir
Ann Arbor, MI
 
Silverado Construction Inc
(586) 758-2600
2055 E 9 Mile Rd
Warren, MI
 

Building a Masonry Firebox with Refractory Mortar

Provided By:

Source: MASONRY CONSTRUCTION MAGAZINE
Publication date: October 1, 2006

By Bob Rucker

Many fireplace masons are not familiar with refractory mortar, or they confuse the product with fireclay mortar. Masonry fireboxes are often laid in ordinary portland cement mortar, sometimes with a little extra cement or some fireclay added to make the mixture “fireclay mortar.”

This approach is not surprising since the major building codes have been unclear, inconsistent, or silent on the subject. The ICC codes – recently adopted in many states –require refractory mortar for the construction of fireboxes, smoke chambers, and flue linings, but a short while ago only the NFPA 211 code called for “refractory mortar (ASTM C199, medium duty).” The BOCA code required “medium-duty fireclay mortar,” the UBC just required that the “joints in firebrick shall not exceed ¼ in.,” and the CABO One and Two Family Dwelling Code did not specify the type of mortar or size of joint to be used.

The problem with using ordinary mortar is that portland cement can't take the heat. Oddly, portland cement retains its strength up to fairly high temperatures, but deteriorates as it cools down through about 600° F. Eventually all that is left of the mortar is the sand and fireclay, with no cement binder. The mortar has no strength and easily falls out of the joints, especially if they are wide.

Refractory mortar, on the other...

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