Should these joists be fixed to stop roof spreading...

[Adam182]

Hi every, recently removed the loft boards in order to reboard with t&g chipboard, I am wondering if the joists should be fixed together that are sat on the central loadbearing wall and connected to only the rafters and not sat on the wall plate at front/back.

I was expecting these to be helping stop spread of the roof but it seems they are under very little tension if any, heres a short video...

https://1drv.ms/v/s!Ag-VaEAvyPSvgbttp9avETto3-Yk7A

Also is there a specific name for this type of roof where the joists are not sat on the wall plate and just connected to the rafters which in turn leaves an angle at the top of the walls in every upstairs room. I have established its a hipped roof but just wondering if there is a name for this specific type.

Thanks any feedback is much appreciated.

 

[^woody^]

It's OK. If it was going to spread, it would have done so long ago. The purlins are preventing spread.

It's called a coombed ceiling.

 

[noseall]

I would fix them together in any case.

 

[datarebal]

Cost nothing to fix them..

 

[Adam182]

Thanks guys! fixed them together and reboarded

 

[rob_j20]

Just out of interest what is the big beam called in the first picture. This is how my roof is constructed but that beam is about 3 times bigger. I have actually added struts from said beam down to the joists to help support them for when i board it out.

 

[Adam182]

Just out of interest what is the big beam called in the first picture. This is how my roof is constructed but that beam is about 3 times bigger. I have actually added struts from said beam down to the joists to help support them for when i board it out.

I also had no idea what that was until recently, it's called a "Purlin" I can only assume it's size relates to how supportive it is of the roof, yours being smaller would suggest it plays less of a role in your roof. I would think it wouldn't need to be as big if it was supported into a solid wall at either end, as mine is a hip roof it is only supported in one wall and continues right around. Hope this helps!

 

[rob_j20]

I also had no idea what that was until recently, it's called a "Purlin" I can only assume it's size relates to how supportive it is of the roof, yours being smaller would suggest it plays less of a role in your roof. I would think it wouldn't need to be as big if it was supported into a solid wall at either end, as mine is a hip roof it is only supported in one wall and continues right around. Hope this helps!

I meant mine is three times bigger supported both ends by the walls.
I like this type of roof gives good space in between the purlins.

 

[Adam182]

I meant mine is three times bigger supported both ends by the walls.
I like this type of roof gives good space in between the purlins.

Wow it's must be a huge chunk of wood in that case! I guess I'm wrong about the reason for their size in that case.