The Frame

A quick exterior survey of the building indicated the sill plates were largely rotten. They were originally squared 8"x10" white oak timbers laid on side. Typically these rot at the outer bottom corner and slowly roll out. This process was well advanced in Ham House.

The Ham House frame was constructed in 4 bents using the square rule method of timber framing with 2" offsets. Contrary to popular sentiment that people of the 19th century did all their own work, the Ham House frame was constructed by skilled and experienced framers. The interior bracing is typical of a German frame, and the knee wall construction, typical of the Ontario timber frame, is also found in northern New York. This is interesting as the first wave of Loyalists to settle Ontario (including the Hams) were from the upper Hudson Valley, many of German origin.

Square rule timber framing was developed in the U.S. around 1800 and revolutionized the speed and ease of timber frame construction. In this method, a 'virtual' ideal timber is imagined within the actual timber. The actual timber is then only reduced to the dimensions of the ideal timber at the joinery. Mortise and tenons are constructed in increments of either 1.5" or 2". This method was made possible by the large trees available in the virgin forests of North America and replaced the earlier European 'scribe rule' method of frame construction. Using the scribe rule, structural timbers were individually fitted and marked prior to actual assembly. Using the square rule, components could be cut at different locations and need only be brought together for assembly.

Though the original 8"x10" sill plates were white oak and the rest of the frame was pine, we replaced all timbers with Douglas fir. Each replaced timber was copied using standard timber framing techniques. This was not necessarily simple as some timbers were so far decayed there was little left to copy. 

The task at hand was complicated by the fact the foundation was in very poor condition - in places well out of alignment with the frame. Contrary to intuition, repairs began from the top down. This was because timber frames are very strong and point-loaded. By lifting at strong points in the frame it could be leveled and foundation repair could proceed undisturbed.

To replace the bent beam and ensure the frame did not move with removal of the original timber, construction lumber was lag-bolted into the uprights above the bent beam and at their bottoms. The top interior wall plank between the windows in the upstairs store was removed and a length of 2x4 bolted to the inside of each 4"x4" stud. A 16' length of doubled 2x8 was placed on a 20 ton hydraulic jack sitting on the main floor (braced in the basement) and the top of the doubled 2x8 was notched to engage the 2x4 bolted to the upstairs studs. By pressing up on the 2x4, the tie beam (that had sagged with rotting of the bent beam) could be flexed upward and the studs themselves pressed upward, preventing them from falling out of their mortises in the tie beam. Once the new bent beam was in place, tenens were slipped through the through-mortises of the uprights into slots cut in the ends of the bent beam, then glued and lag-bolted to the bent beam. Finally, the bent beam was pegged in place with 1" white oak pegs.

To replace sill plates, the building needed to be lifted. At corners doubled structural lumber was placed on 20 ton hydraulic jacks and a notch in the tops of the lumber engaged with the girt and bent beams near the uprights. Within the building door frames were removed and 20 ton jacks used to press upward on the interior bent beams near the uprights. Short lengths of 2x4 were lag bolted between the tops of 4"x4" studs and the girt and bent beams to prevent them from falling out of their mortises while the frame was lifted.