HPM Heatproof Mortar is a ready-mixed mortar for suitable thin refractory joints. However, it should not be chosen for a garden barbecue just because it withstands high temperature well. Before opening the package, check if the specific location also meets the requirements for moisture and protection.
Temperature and weather are two separate conditions
Vitcas HPM Heatproof Mortar has a declared resistance up to 1400°C. The manufacturer describes it for indoor uses or those not exposed to weather conditions. An exposed garden firebox does not meet those conditions simply because a small canopy is added.
For outdoor use, the manufacturer indicates protection against moisture through appropriate roofing or another weather-resistant layer. Assess the entire system, including water access from the base. For joints exposed to rain, consider a material intended for this purpose, for example Outdoor Oven Cement.
Fit the bricks before preparing the mortar
HPM is intended for the specified thin joints. Lay out a few elements, check the dimensions, and remove loose debris from the connection area. Large unevenness is not corrected with an arbitrarily thick layer of this mortar; the manufacturer does not describe it as a material for plastering or filling larger gaps.
Determine the preparation of the bricks and the contents of the package according to the current instructions. The ready consistency does not justify independently adding another binder or unmeasured water. Prepare the tools in advance to maintain the repeatability of the connections being made.
Check fresh joints and storage
After bricklaying, remove residues according to the instructions before they hinder the inspection of the connection. Do not treat a dry surface as proof of the entire device's readiness. Drying also applies to the bricks and other new layers.
Close the container of unused material and store it under permitted conditions. Keep the batch number and product data sheet. If the roofing or barbecue finish changes later, return to assessing the mortar application conditions instead of assuming they remain the same.