The Foundation

The foundation of Ham House was the single main reason this project took twice the time expected. The foundation appears to have been built before the frame, and housed a full basement. Despite being built from weathered fieldstone, the foundation stones were laid like block. In this unusual masonry technique, a row of large stones was laid down, and a thin 'shim' layer laid on top of that to create a new level course. Below grade the blocks were laid up dry (without mortar) from inside the basement. These stone blocks were large, some in excess of 1000 lbs. Presumably gravity was meant to keep them in place. Except for random stones in the mud, the exterior face of the wall did not really exist.

Figure 1. Original wall section

Above grade the wall was constructed wet (with mortar) to a thickness of about 24". The stones were semi-rendered meaning the mortar joints were smeared over the stones in an effort to create a flat surface over the entire wall. Very little of this survived on the exterior, but the interior rendering was largely intact.

From the 1890's maple trees were planted along the east and north sides of the building. One last immense red maple was still standing at the southeast corner of the building at the outset of this project. The dry stone courses of the foundation made easy access for the tree roots and the SE corner of the building had been pushed completely out of alignment with the frame. There was originally a basement access door in the east wall and this provided a weakness where the bottom of the wall had been pushed in nearly 18". The north and south foundation walls spanned of 38'. The south wall was supported mid-span by a concrete cistern wall. The bottom of the middle of the north wall had moved roughly 6" by the action of lateral earth pressure.

Figure 2. Orange sections were entirely rebuilt. Green sections were grouted below grade and underpinned on the outside with corbelled masonry.

The west wall was constructed more as a standard rubble wall with smaller stones, and was supported on the inside over half its length by a 40" deep chimney foundation. The west wall had not moved.

In 1956 the foundation had been parged, apparently in an effort to deal with movement. This parging extended only to grade and the east sill plate sat almost entirely on the parging. As the parging was waterproof and much harder than the still-moving underlying masonry wall, in many places the parging had separated from the masonry.

Figure 3. Laying up the new wall

It was decided to completely rebuild the east half of the south wall and the entire east wall. Below grade the new wall was built as a reinforced concrete cantilevered wall to ensure it would remain static. This wall was 24" thick and above grade the original stones were laid in the same manner as the original wall.

Figure 2. Cleaning out the mud

The north wall was grouted from the inside and re-pointed above grade. Below grade the mud was excavated in sections, removing any loose stones. An outer stone wall tied into the original wall was then constructed below grade with stones left over from the newly built east and south walls, corbelled out so to be directly under the outer edge of the wall at the top.

Figure 4. North wall rebuilt

To accommodate the new addition that will have a deeper basement than the old building, the south wall where the addition is to be built was underpinned to the bedrock with leftover stone.

One impressive find in the foundation were two iron-barred windows, still unglazed. One was partially embedded in the 1956 parging and was stuffed with insulation. The other was entirely encased in the cistern concrete. The cistern window faced under the addition and was still shuttered with the original 1816 shutters.

Figure 5. SE barred window semi-parged

Figure 6. SE barred window removed

Figure 7. SE barred window restored

Figure 8. SW barred window original shutter still in place

My first thought was - were these to keep people out or in?

The eastern window was moved about 3' to the east so as to make room for the new addition. The western window was removed entirely and re-located to the NE corner of the east wall. The opening of this window was used to pass infrastructure from the new utility room into the old basement through the 24" thick foundation wall.