Firebrick for fireplaces: red and buff, full and split

Firebrick: what we stock

Fire brick sizes

Firebrick is ordered by shape and size, and sizes vary by maker. We stock one full size, 8.25" x 4" x 2.25", plus splits, in red and buff. The chart sets our brick beside other common shapes, so you can match an existing firebox.

Sizes other than Yankocy's are common industry shapes; exact dimensions vary slightly by maker.

When do you use split firebrick?

Splits have the same face as a full firebrick at about half the thickness. Masons use them where there is less depth to work with in a firebox or hearth, or to face over existing masonry. Full firebrick goes where the firebox wall is built to full depth.

What is the difference between red and buff firebrick?

The two colors do the same job; the choice is how the firebox looks. Buff is a yellow-white brick that can run toward orange or gray, and it is the most common firebrick. Red carries flecks of buff and ranges from red to orange. Fireplace firebrick of either color is made to ASTM C 1261, the spec for firebox brick.

Estimating mortar and hardware

• Mortar: about 50 lb of Heat Stop lays about 100 full firebrick at a 1/16" to 1/8" joint.
• Lay firebrick in refractory mortar meeting ASTM C-199, not regular masonry mortar or fire clay mixes.
• Order Vestal dampers, cleanout doors, ash dumps and outside air kits on the same delivery.

Questions about firebrick

What are the standard sizes of fire brick?

Sizes vary by maker. The common large full firebrick is 9" x 4.5" x 2.5", with a 1.25" thick split, and makers also offer smaller 9" x 4" and 8.25" x 4" shapes. Yankocy stocks an 8.25" x 4" x 2.25" full firebrick, 567 to a pallet, and splits at 928 to a pallet, in red and buff.

What is the difference between red and buff firebrick?

Color and look. Buff is the yellow-white firebrick most fireplaces use, with normal variation toward orange or gray. Red firebrick runs red to orange with buff flecks. Yankocy stocks both colors in full and split, so a mason can match the firebox to the job.

Can firebrick be cut to size?

Yes. Firebrick is cut on a masonry saw like other brick to fit the firebox back, sides and hearth. Where the problem is depth rather than length, a split firebrick, about half the thickness of a full one, often avoids the cut altogether. Yankocy stocks splits in both red and buff.

What mortar is used to lay firebrick?

A refractory mortar that meets ASTM C-199. Heat Stop 50, a dry mix in 50 lb bags, is non-water soluble after it sets and is rated for applications well over 2,000°F. Figure about 50 lb of Heat Stop per 100 firebrick at a thin 1/16" to 1/8" joint.

Where can masons buy firebrick?

From a local mason or masonry supply yard. Yankocy sells red and buff firebrick wholesale to those yards and dealers, delivered on its own trucks across Connecticut and nearby states. Call (203) 261-4955 or email info@yankocy.com.

Last updated November 2, 2026

Yankocy sells firebrick wholesale to mason yards and dealers, on the same truck as Heat Stop and flue lining. Buying for your own home? Your local lumber or mason yard can order it for you.

Firebrick data sheets and sources

• Heat Stop FAQs: mortar per 100 firebrick, ASTM C-199

Related to firebrick

• Heat Stop refractory mortar
• Clay flue liner
• Steel lintels
• Mason lime (Type S)
• All fireplace & chimney