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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 TWO

FOUNDATIONS

Building contracts frequently stressed the importance of achieving a solid base. Success depended on several factors: the building site, the type of construction, and the care taken during the building stage. At Louisbourg, proper site development varied from clearing trees, removing imbedded or scattered boulders, draining or filling in insect-infested swamps, or adapting to loose beach material.

A foundation was not a requirement to piquet construction, but a solid base was no less important there than in a building type like charpente that had an underpinning. In piquet construction, a trench, 18 pouces to 2 pieds deep (then back-filled), was the anchor since walls were buried directly in the ground. If the land, as with a swamp, were not suitable for digging, then perhaps a builder would have driven his piquets, as one did the support piles of a charpente house in Block 5.

Ground level decay, inevitable in this type of piquet  construction, perhaps persuaded some builders, familiar with military palisade and fencing techniques, to have first charred the ends of the piquets before planting them, or, as with boundary markers, to have set pieces of coal beneath their ends, or, using common sense, to have placed root ends up rather than down in the ground. Others, of a more fundamental bent, however, practiced a more traditional approach - of raising walls out of the ground.

This method entailed wooden underpinnings not unlike sleepers (joists), but employed words like solage, solle, or soller that were reminiscent of the nomenclature of charpente construction - even though foundations there were usually, though not always, of masonry. A 1717 plan clearly depicts this alternate piquet technique, its buildings illustrated in section with underlying support systems that raised the piquet walls out of direct contact with the ground. In such cases builders had placed a set of spaced members on or in the ground, with a second set on top running perpendicular to the first, so that these wooden solages rather than the walls proper would have begun to rot first. Nevertheless, over time, rot would still have spread to the walls, as the solages absorbed and transferred moisture.

The foundation of a charpente building, a superior technique for controlling the decay of wood because it elevated wooden members above ground level, was of masonry, usually rubblestone with a long-lasting mortar bond. Although the Spanish traveler, Don Antonia De Ulloa, who visited Louisbourg in 1745, inexplicably described foundations as generally 2 to 2 1/2 yards (varas) high, they were rarely even one-half storey. Indeed, foundations were generally 2 1/2 pieds high, though some were below grade level and others, as under the Block 2D house, sufficiently high enough to produce a raised basement or cellar.

A masonry foundation was not only good preventative maintenance, protecting main perimeter sills, flooring joists and even the corridor sills of an early government building from rot, but it was also vital to the proper transfer of a charpente building's charge into the ground. Thus, to achieve a solid base, un bon fond as the contracts described it, some, though not all designs, notably several for charpente buildings on Isle Saint-Jean, indicated separate and distinct footings beneath the foundations. Other builders, however, likely achieved the same result by first dropping the largest stones into the trench (which, for example, took a 23A builder of a charpente storehouse eight days to dig).

Known foundation thicknesses ranged from one to 3 pieds. Rubblestone was the most popular masonry material, but other available stone materials, though never directly specified, were brick and flatstone. Just west of Block 1 the builder of the Lartigue house chose a faced stone, while another, at Block 20G, opted for an unspecified decorative material.

It was unusual to find a charpente building on Isle Royale with a foundation other than masonry. In Newfoundland, piquet piles, post and planks and dry masonry were alternate approaches. In Louisbourg it was piles, driven into a drained, swampy area. Then, on Block 5A, the carpenter who was to assemble an imported New England charpente building on the site, was to mortise and peg to the top of these piles or solage, the 7 by 8 pouce sills (each no less than 20 pieds long) upon which the building was to sit.

A charpente building without a foundation was another possibility, though no record in Louisbourg has survived. Small constructions like latrines were prime candidates, and even larger buildings were a possibility. Historical plans, notably those of the Block 14G house or of a Fauxbourg residence, illustrated buildings without obvious foundations, though the underpinnings, of course, may have been below ground level, out of sight.

In rubblestone masonry constructions without basements, a builder often excavated a 2 1/2 to 3 pieds deep by 3 pieds wide trench in which to build a 2 1/2 pieds wide footing as support for a 2 pieds wide perimeter wall. Dimensions varied, of course, depending on the site, a building's downward charge and on the builder's requirements: Port Toulouse foundations were 2 pieds wide with their supporting walls being only 1 1/2 pieds thick; on Block 34C they were 3 pieds, that is, as wide as the excavation ditch itself, but they supported walls only 2 pieds thick; and in Isle Saint-Jean, for a powder magazine, the foundations of the gable ends were less thick than those of the long sides.

For a masonry structure with a basement, like a proposed Block 2 Rodrigue residence, the contractor chose to excavate completely down to basement level and raise his rubblestone walls between two guidelines rather than against earthen limits, which was another possibility. Unfortunately, he did not specify how thick the foundation was to have been, instead indicating that the main walls or murs de face, which were to rise off this bon fondement, were to be 2 pieds thick throughout, from top to bottom. Another option involved simply hollowing a basement out of the ground after the house was constructed, as was done with a charpente house on 5D.

Not every contact specified separate or distinct footings, but some did. On Battery Island, for example, the foundations and walls for the guardhouse and prison, as well as the trenches, were to be a uniform thickness of one pied 6 pouces. By way of contrast, in the masonry buildings of Port Toulouse (1733), builders used the footing-foundation technique to achieve a stable base. In addition, the principal walls of the commander's lodging at Port Toulouse were built in the middle of the footings, leaving a ledge to either side. Builders could have benefited from interior ledges as a matter of principle, using them to support their flooring joists, but not all builders did, some instead constructing their walls to the inside edge.

A proposal for a Block 3 masonry church, dealing at some lengths in 1739 on the requirement for a well-constructed foundation, was quite concerned with Louisbourg's extreme, destructive frost/thaw cycle, the movement and uneven settling of walls, and the resulting high maintenance costs. Of particular concern was the expansion caused by freezing. The solution: well cramped cut stone quoins, door and window surrounds, and a cut stone footing-foundation (socle) that rose at least 2 pieds above ground level.

A masonry footing or foundation sometimes required additional support to achieve a firm basis. In 1718, recognizing that the King's Bastion barracks, the first large masonry undertaking on the island, might require such help, the proposed contract allowed the contractor two options: he could place beneath the masonry foundation a wooden grillwork, of reinforced iron-tipped pointed piles, no greater than 12 pieds long and no smaller in circumference than 9 to 12 pouces at the small end; or, instead of the grillwork, he could substitute boards, perhaps 18 pouces wide and 3 pouces thick.

Other comments on foundations were less enlightening. Some officials thought that piquet structures, with walls planted in the ground, would last 12 to 15 years but that pièce-sur-pièce structures, at Port Dauphin for example, of an unknown foundation type, would last 40 to 50 years. Elsewhere, in the case of a proposed pièce-sur-pièce a machicoulis tower, the foundation was masonry.

Finally, a Block 1 winter housing project proposed a 2 pieds high foundation for a vertical, wooden post wall construction above. In contrast, the vertical load-bearing spaced masonry pillars, and infills between, of the original Block 1 engineer's house, had no apparent underpinnings at all.