Change in pitch - 30s roof frame Information, help and tips on many areas of roofing including trusses, tiling, venting, insulation etc....

[mortarboard]

I need to match my existing house roof for the front corner of an extension. The existing roof is old clay tiles at 45 degrees but the bottom 9 rows flare out at a shallow angle over a wide soffit. A lot of the local houses have this type of roof (1930s). It looks like a simple 45 slope in the loft so there must be some extra bit on the edge or something. Can anyone tell me where I might find a diagram of the structure to make this corner? Even just the name of the feature would be helpful at this stage! Many thanks

[chris_on_tour2002]

unlikely you'll find a diagram. it was probably done with a tapered run of timber fitted to the trusses. could be wrong but that's how i'd do it.

[LCL]

mortarboard

This is a fairly common feature, they are rafter spockets, rafter arms or rafter feet bolted or screwed to the existing rafters. The rafters will bear onto the wall plate as normal and then the sprockets are screwed to the sides of the rafters to form the low level detail. When you open the roof up you will see this. It should be quite simple to replicated.

Hope this helps.

LCL

[mortarboard]

Thanks for that LCL.

I'm not going to open up the old roof because this will be a completely separate new section at a lower level. But from what you and chris_on_tour2002 are saying it sounds like I should use standard rafters sitting on my wall plate. Then add a horizontal piece that sticks out to form the wide soffit. Then fill in the shallow angle at the bottom with a short slope that tapers back up onto the main 45 degree rafters - forming a small triangle on the outside at the bottom.

I assume I can fix these extra bits onto the main rafter with coach screws?

[mortarboard]

Just an update if anyone was interested...

I have been given an old book called Building Construction Volume One by W B McKay (1938) and this has some very detailed diagrams of my exact feature on P139.

It's pretty much exactly as described by the help here - so thanks!