SparrowLegs Renovates holiday Gite, Collar Beam - End of week 1.

By the middle of the week one, the first floor had been gutted. This gave us a clean canvas to translate the design done on Sweethome 3D to the first floor. This was a rough translation as the real world environment highlighted faults with the CAD design and the inaccuracies with the original measurement plotted on the CAD program. (Actually, this was only out be 30mm max.)



(SweetHome 3D CAD Software)

The existing Ergonomics of ceiling height was to low, sitting at 2.15 meters. Increasing the height was possible, but governed by the Collar beam.

The Collar Beam in this project is under compression rather than tension as it keeps the Common rafters from sagging. If the Collar Beam was a around a third up from the base of Common rafter, then this would have been under tension, preventing the weight of the roof pushing the walls out of possition or the Header Beam (Wall Plate) from detatching from the outer wall. This is also called a Collar tie, generally a misused name for Collar beams under Compression.

(Collar Tie)

 

(Collar Beam)
 

Also another point particular to this project and a factor regarding any decisions moving the Collar beam was the understanding of traditional roofing techniques in rural France. This roof spreads the load on the Wall plate by using a Hammerpost (or internal Sprocket) scarf jointed to the Common rafter. These where both then held into position using a Hammerbeam and some bolts.

(A - Common Rafter, B - Hammerpost, C - Bolt, D - Hammerbeam.)

By measuring the distance between the Ridge beam and the Hammerpost and knowing that the Collar beam in under compression, I was able to increase the ceiling height by 250mm by moving the Collar beam. This wouldn't cause any issues and increases the ceiling height to become standard. (Well, standard in the UK! - In the uk, the standard ceiling height is 2.4 meters, or 8ft - 38mm difference. This height is why plasterboard in the UK 2400mm * 1200mm.

Collar beams raised ready for the new ceiling studwork to be installed on week 2.