Outdoor fireplaces add beauty to any home and provide a focal point for outdoor entertaining. An outdoor fireplace requires relatively little maintenance, but one area that needs occasional attention is the mortar. If the mortar between the stones or bricks begins to crumble, crack or fall out of the joints in pieces, it needs to be repaired.
Repairing crumbled mortar is referred to as tuckpointing. The cracked and crumbling mortar is removed using a chisel or a grinder and the joint is cleaned. Then, fresh mortar is pressed or “tucked” into the joint. Keeping the mortar in good shape is important because it keeps moisture out of structure. If water gets into the damaged joint or crack, it can speed up the deterioration process, especially in areas of freezing weather.
Applying the mortar to the joint can be accomplished either using a mortar bag similar to a pastry bag or by “sweeping” a small amount of mixed mortar off of a trowel with a tuckpointing tool. In either event, the object is to firmly pack the joint with fresh mortar. It is a job that looks easier than it is and unless you have the tools and some experience handling mortar, it’s a job best left to an experienced landscaper or mason.
Be sure to inspect the inside of the firebox as well as the exterior of the outdoor fireplace. The firebox is usually lined with fire resistant brick and replacing crumbled mortar is done the same way as tuckpointing the outside brick or stone structure except that special heat resistant mortar called “refractory” mortar should be used. This mortar can withstand higher temperatures than ordinary mortar so it is less affected by expansion and contraction associated with the heating and cooling of the inside of the fireplace.