Replacing a purlin

[WyteNyte]

I have a 1930s semi with a large hip roof. It has purlins on each of the 3 slopes supporting the 4x2 rafters. These purlins are themselves supported by centrally positioned diagonal timber struts to load bearing walls.

I would like to make an "occasional use" hobby room in this loft, and to provide more clear space I would like to remove the purlins and associated struts. To provide the required rafter support my idea would be to insert 100x50 collars fixed between each rafter across the roof space at about 2.4m above loft floor level (The ridge is some 4.2m above the floor). Additional support would be provided by 100x50 timbers from the rafter to the floor at about 1.2m above floor level.

Is this a feasible and structurally sound solution? If so, what form of connection should be used between the rafters and the new timbers?

 

[noseall]

in order to remove something as structurally important as a purlin, would require a detailed remedy from a structural engineer

the engineer would need to factor in various loadings from wind and snow, existing roof tiles, timber connections, strength of walls carrying loads, remaining clear spans, condition of timber junctions upon removal of purlin, etc, etc.

there are too many variables to take a guess.

 

[WyteNyte]

Thanks for this.

It's a trip to my favorite structural engineer then!! I guess I had hoped that someone who had done something similar would be able to say if what I was talking about was sane or insane

 

[noseall]

ask 'shytalkz' in the building section.

 

[WyteNyte]

Sorry, I'm new to this forum; how do I do that??

 

[JohnD]

//www.diynot.com/forums/viewforum.php?f=13

 

[WyteNyte]

Thanks, I have reposted the query on that forum.