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Researching the Fortress of Louisbourg National Historic Site of Canada
  Recherche sur la Forteresse-de-Louisbourg Lieu historique national du Canada

DOMESTIC BUILDING CONSTRUCTION 
AT THE FORTRESS OF LOUISBOURG, 1713 - 1758

By

Eric Krause

1996 Draft Report

(Fortress of Louisbourg
Report Number H G 10)

CHAPTER EIGHTEEN

CHIMNEYS AND CHIMNEY OPENINGS -
CHIMNEY CONSTRUCTION

The best mortar was a mixture of one-third lime and two-thirds sand. Properly prepared, which often was not the case, especially in its use in fortification works, it was a strong and lasting chimney mortar. A weaker, though frequent substitute, particularly outside Louisbourg itself, was a mortar that was clay-based.

Most chimneys were either of local rubblestone or of New England imported brick. Some were also of local flatstone. A few, generally in the countryside or on Isle Saint-Jean, were even of clay and straw, probably placed in a wooden frame.

Builders also constructed chimneys of local bricks, which enjoyed some popularity in the early years when there existed a kiln at Port Toulouse. Local bricks were a poor choice for exterior use, however, for their quality was exceedingly bad. The stacks at the King's Bastion barracks, for example, made from local bricks had deteriorated to such a state by 1730 that the engineer, Etienne Verrier, proposed a complete renovation in local flatstone.

Local flatstone was little better than local bricks, however, and by 1736 the flatstone stacks of the Island Battery were in a state beyond repair. The investigation, which showed the flatstone to have been too thin, recommended a complete renovation instead, in well-cramped cut stone. The stone was to come from a number of demolished embrasures.

Chimneys of mixed materials existed as well. On Block 5 the Dibarrat house of 1721 had a chimney of stone and earth mortar from its foundation to above its attic floor. From that point the chimney continued upwards in a mixture of clay and straw. Of similar construction was a 1749 Isle Saint-Jean forge whose chimney was partly in rubblestone and partly in clay and straw. Also on the island was a piquet complex with a chimney in rubblestone and clay mortar to above its floor. Its stack was wood framed and infilled with clay and straw.

Several Isle Royale proposals describe gypsum plaster chimneys in good detail, no doubt because the military held them in some regard. However, it is safe to say that none were actually built on the island. One view even held that gypsum deposits were not found commonly on Isle Royale, and that it was of an inferior quality and so would not stack properly in the kiln. Consequently, not only did it cost more, using local labour, to stack it than to burn it, but a third or more was lost when burned.

There were also chimneys that were temporary or primitive. A barracks set up at the Royal Battery during its construction stage had a chimney of rubblestone, bonded with a lime and sand mortar. Some tents even had chimneys. Among the most primitive chimneys, however, were those that fishermen or persons wintering in the countryside would have built of dry stone (perhaps with a clay mortar), and those that some former inhabitants of Louisbourg built on Saint Pierre and Miquelon after 1758. There, perhaps like on Isle Royale earlier, fireplaces were built without benefit of stone or bricks, with flues and chimney stacks of boards instead.