3 Westgate Street, Southery.

PE38 0PA. United Kingdom.



01945 660504


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Traditional Construction and longspan floorjoist design

The practice was tasked with the structural design of new floor joists for an existing Georgian building. The aim of the design was to span floor joists from solid internal masonry partition to exernal masonry wall, thereby allowing for the removal of an existing steel downstand beam that cut right through the large room, reducing the ceiling height and encroaching on the existing headroom.

Interestingly, in designing the new floor, it soon became apparent that a span of 5 meters would result in joists 75mm wide x 225mm deep, just to remove the excessive deflection and resultant vibration in the first floor. An existing roll topped bath, set freestanding to the first floor bathroom would have otherwise caused a “camber” in the floor as it was filled and emptied.

The attic space incorporated a series of large water tanks, supported directly off an internal partition, running from first floor ceiling, down to ground floor ceiling and existing joists, spanning onto the steel beam, carried all this load. A key issue was therefore the mass of the masonry on the joists and the loads applied by the water tanks. Re-location of the water tanks was a viable option and the masonry partition, discerned as being free-standing would require demolition, with timber stud-work a suitable replacement.

Timber cut roof to stately home

Design of joists to the location of the roll top bath was limited to “doubled up” sections, picking up the extra loads imposed by the cast iron tub and water it contained.

CAD drawing of new floor joist layout

Finally, there was the matter of joist hangers, as the client wanted to “retrofit” the joists from the ground floor, limiting the damage that would otherwise occur in the existing first floor bathroom. Opting for Simpson Masonry joist hangers was clearly the most suitable solution and they were designed to fit into slots, cut into the masonry, so that new joists could be sited in between existing ones.

Simpson Masonry joist hangers