Purlin supports in oak framing

[wobblydoggy]

I have worked out the wall plate and the ridge support and I have end and central ties from back to front.

To stop sag in the middle of this 8 metre purlin I want to put a support in from the back to front tie.

What angle should it be at to the purin?

Straight down and cup the purlin or at an angle?

Cheers

Wobbly

 

[fretnot]

Vertical or angled would be fine depends where you have something to transfer the load like an internal wall or a binder.
I would like to see two over a 8m run

 

[wobblydoggy]

Vertical or angled would be fine depends where you have something to transfer the load like an internal wall or a binder.
I would like to see two over a 8m run

So would I but just not possible, so I have upped the timber size

 

[zb1]

What size purlin are you using and do you have a drawing or sketch? if there is a good bearing surface at each end and the purlin is of a reasonably size and quality then 4m spans should be fine. The purlins should be supported by principal rafters off of the tie beam as should the ridge except if you have king post trusses when the king post carries the ridge. Just cupping the purlin onto the tie beam is not ideal. The tie beam should be in tension from the truss not in compression from vertical load. What span is the tie beam and size?

 

[wobblydoggy]

What size purlin are you using and do you have a drawing or sketch? if there is a good bearing surface at each end and the purlin is of a reasonably size and quality then 4m spans should be fine. The purlins should be supported by principal rafters off of the tie beam as should the ridge except if you have king post trusses when the king post carries the ridge. Just cupping the purlin onto the tie beam is not ideal. The tie beam should be in tension from the truss not in compression from vertical load. What span is the tie beam and size?

3 metre span 175mm x 125 mm

 

[zb1]

Is that tie beam size? What is the truss shape? Is it one truss at the mid span of 4m with masonry at each end supporting purlins and ridge or is it 3 trusses? 175*125 seems a bit small over 3m for a tie beam but it depends on the truss design and how the load is transferred. Can you provide a sketch?

 

[wobblydoggy]

Is that tie beam size? What is the truss shape? Is it one truss at the mid span of 4m with masonry at each end supporting purlins and ridge or is it 3 trusses? 175*125 seems a bit small over 3m for a tie beam but it depends on the truss design and how the load is transferred. Can you provide a sketch?

The Terrace is 8M x 3M (Plus a 1 Metre Strip)

I Have uprights at 1m - 3.4M - 5. 8M and 8

All tied front to back by 175 x 125 that span 2.8 M between uprights

So Purlin supported @ 3.4 + 5.8 and either end

Peg tile roof on top