Adhesives for the Hearth
Adhesives and Cements for Installing and Servicing Hearth Products
Many of the visitors to Hearth.com have asked about which products to use when considering the medium and high temperatures that stoves and fireplaces are exposed to. Following are some general guidelines as to product types which fit specific needs.
Note: Products which are sold as "Fire Block" caulk and foam are NOT to be used in stove and fireplace installation or service.
Reason: These products are designed for installation and use at regular temperatures. Their only fire function is to stop the spread of fire from one room to another (similar to fire rated sheet rock, etc.).
The products I have seen with these names are designed for enclosing around wires and pipes and other large holes which might be through walls and floors that are fire rated, meaning that a fire in that room takes a certain amount of time to spread to any adjoining room. As you can see, that has nothing to do with stoves, etc.
DO NOT BE FOOLED BY THE LABELS ON THESE PRODUCTS! One product we researched said this on the spec sheet:
"RS 136 cannot be used in areas where.. where there are continuous temperatures above 120 F "
This makes it vastly lower in temperature rating than the other products we will discuss in this article.
Here are some products which are commonly used by pros in the Hearth trade:
1. Silicone, for lower temp uses such as where a Damper block off plate hits the fireplace wall (insert installation) - also hi-temp silicone is often used for pellet and gas vent and for storm collars on metal chimney. Regular silicones are often rated to 400-500 degrees, with black and red (or orange) formulations being tested up to 600+ degrees F.
Silicones are not rated high enough to use in direct contact with stove fireboxes or chimney liners/single wall pipe.
2. Furnace cement (usually silicate based) for up against the pipe - Rutland Black Furnace cement is a popular brand of this. This can be used for everything from the rebuilding of cast iron stoves to sealing single wall stove pipe joints. The temperature rating for furnace cement can be 1500-2000+ degrees.
Stove gasket cement is usually a thinner mixture, but is similar to furnace cement.
3. refractory cement is used for patching larger holes and firebricks. It usually has a buff or white color and is available premixed, in caulk tubes or as a powder which you can mix with water. refractory cement (specifically "castable" refractory) can be used to fabricate (mold) replacement for certain fireplace and stove liners when the original replacement parts cannot be located. This is done by making a wooden mold to the proper size and pouring the cement into it.
4. Thinsets, epoxy, grouts and mortars - are usually used in lower temperature (under 200 degrees F) applications, such as stove hearths (the floors below a stove), rear wall protection and fireplace facades. In many of these cases, the surface temperature is unlikely to reach above 130, and most products can take that kind of low-level heat. However, if your application is likely to get much warmer than that, please read the label of the product you intend to use. Example: epoxy tile cement can be rated for service at 160 degrees F , while some premix thinsets are only 120 F.
The above information should help you service or install your stove in a more professional and safe manner