Feature Truss and Purlings?

Question

I'm fitting 3 structural feature trusses with timber ridge purling. One end of the room is into a chimney stack and the other onto a 100mm block wall, My question is "How do I fit the Ridge purling to the chimney stack end of the room".

Answer 1

I think what you got hear is ridge beam or board not a purlin, purlins are usually applied to top side of trusses, beams or chords to stiffen and provide sub-structure for the attachment of sidings and or roofing materials. That said, a pocket must be cut into the chimney if this is weight bearing and not asthetic only.

The trusses sound more like rafter beams bearing on walls and sandwiching the ridge beam, for if they were trusses the weight would be carried at the walls not at the peak in pockets the ridge beam rest with-in. Do you have a bottom chord as well, a king post or W truss. Trusses have either blocking between each or continous strapping over chords that may or may not be left in place, prior to installation of roof sheathing. Trusses may be cross braced internally to prevent racking or attached as you describe at the top peaks but I don't see a purlin being used!

So is it weight bearing or faux construction? Are they trusses or rafter beams and if so at what centers?

I may be totally wrong, an you have weight bearing "Queen Post Timber trusses" per example, but that being the case, the purlin you described , is there to prevent racking only and the pockets, carry the purlin's dead weight only...

All trusses transfer weight to walls, at bearing points that transfer weight through structure to foundation and onto footings.

Answer 2

I have been a Joiner for 35 years, but I am not sure what you mean!! , is it Structural, or is it just a feature, look at any large roof you will see the chimney is to one side of the roof, usually the back, that is because the chimney breast is NOT a load bearing structure and all timber should be kept at least 2" (50mm ) away because of the heat that can be generated, If you are talking of a Ridge-purling, the last time I saw one was on the roof of Liverpool Cathedral with a roof span of 80ft, a Ridge-purling sits on top of a King-post truss, a ridge plate is supported by the Common rafters, Purling are supported by the Principal rafters on a truss e.g. King post, Queen-post, A frame,so-on so-on, nothing in a roof would be supported by the chimney breast, if this is structural you would have to redesign the roof or move the chimney, If this is just a feature ,a small hammer-head bracket, or a joist bracket sprayed gold screwed to the chimney breast, don't go knocking holes in it unless you have to , you could damage the liner inside it,
Good luck, have fun.

Answer 3

Your mason should have left a pocket for you to land the purlin in. You may have to have a steel fixture made to bolt to the chimney stack and let the pulin rest in, like a saddle.

Answer 4

Yeah! Husker Du! The Raconteurs - Blue Veins the intro, and the backwards vocal bit BQs: The Olivia Tremor Control - I Have Been Floated and I'm listening to the album Hex Enduction Hour by The Fall

Answer 5

Purlin. :)