Repair Detail 24 years later

This Finnish style contraflow masonry heater and cookstove were built in the Autumn of 1991 on the Lake St Pierre Archipelago, Quebec.

Both heater and cookstove are connected to the same 8 x 12 inch chimney flue. The heater has been fired by the same person every day, often with 2 fires per day, every season for 24 years.
The cookstove has been used only occasionally.

The refractory core follows the 1984 Finnish Fireplace Construction Manual, i.e. the traditional Finnish model with sloped fire box ceiling and 3 inch wide throat. The side channel walls are in common clay brick, layed flat in clay mortar making the walls 4 inches thick.. The fire is fed with under air.

The fire box showing no spalling and minimal mortar loss from the joints. The fire box floor and base of the walls were originally lined by a row of skew cut refractory brick. Only one of these brick remains mortared in position, the other 7 have long since broken free and been discarded.
The grate was replaced last year.

Detail of the back right corner of the fire box. There is some cracking in the wall, but this probably happened years ago and is of little relevance.

View up through the fire box. One full brick, layed lengthways across the lintel, has cracked down the middle along its length, and from side to side across the middle. Three quarters of the brick have fallen, or been pulled away, while one quarter has remained in position.

The remaining piece of brick was removed and a new full brick layed onto the lintel.

New skew cut pieces of brick were cut and layed into position. They would brake free quite quickly if mortared in to place, and so are layed dry.
The function of these pieces is to help concentrate the embers on to the grate during the latter stages of the fire.

It can be seen that this heater has endured almost 25 years of continual seasonal use until needing to be repaired. The repairs made are minor and of little consequence. The condition of the fire box and throat is good. It can be supposed that the heater will be operational for many years to come.

Marcus Flynn


Articles by Marcus Flynn

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