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'.

Quadratic Masonry Llc
(734) 663-9646
3877 Albert Dr
Ann Arbor, MI
 
A & A Construction
(517) 367-0000
1039 1/2 S Pennsylvania Ave
Lansing, MI
 
Expert Construction Co
(586) 293-0920
31056 Shawn Dr
Warren, MI
 
Rose Tile & Masonry
(734) 662-8004
1917 Dunmore Rd
Ann Arbor, MI
 
TheBrickMasters.com
(586) 246-7848
137 Miller St.
Mount Clemens, MI
 
Dunritebrick
(586) 738-7498
42356 Parkside Cir
Sterling Heights, MI
 
Hane Tile & Plastering Mason
(734) 971-8298
2771 Lookout Cir
Ann Arbor, MI
 
Tip-Top Chimney Sweep
(810) 234-5000
3714 W Court St
Flint, MI
 
Debacker & Sons
(586) 775-8700
21750 Schmeman Ave
Warren, MI
 
Masonry Aesthetics Group
(616) 742-9970
1350 Scribner Ave Nw
Grand Rapids, MI
 

Building a Masonry Firebox with Refractory Mortar

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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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