Temporary propping for demolition

[willbish]

I need to prop my neighbours roof while we demolish and rebuild a knackered section of the party wall.

 

I've come up with a propping arrangement but both my neighbour and I want a bit of reassurance this would be sufficient.

 

My structural engineering has passed the buck claiming his insurance does not cover him for temporary works. Im not after calculations just a nod that what we've proposed will stand, and stay standing!

 

If there's keen 'hubbers who could take a look and offer any feedback that would be greatly received.

 

Photos and .pdf attached

Propping arrangement.pdf

[PeterW]

I’d want two props on the middle purlin, and both sets need lateral restraint to stop the roof racking away from the other wall. 

 

Much easier to just put 3 or 4 acro’s per beam to spread the load but make sure there is something stopping the beams moving sideways.  

[Russell griffiths]

That looks spot on, very well thought out and brilliant sketching. 

 

What i would add is you are supporting under both the purlins, just check that there are some fixings between the rafters and the purlins,

if you can’t get in to add some fixings you could cut some of the flat steel strapping, the stuff that comes on a roll and strap over a rafter and into the face of the purlin, just to be sure they don’t twist or slide. 

[Nickfromwales]

Plus 1 on the second support on the mid purlin. 

Whats is the floor construction that these are all sat on? 

[willbish]

Thanks for your input.

 

A second prop on the mid purlin wont be a problem.

 

Im not worried about the rafters sliding, they have battens on top.

 

The ground underneath is about a foot of old sandstone scalps. Was thinking i might chuck down a piece of osb to spread the load but I don't think this is necessary

[Russell griffiths]

If you chuck a scaffold board on the floor and screw your props to it, they won’t twist as you tighten them. 

Winner winner chicken dinner. 

[willbish]

23 minutes ago, Russell griffiths said:

If you chuck a scaffold board on the floor and screw your props to it, they won’t twist as you tighten them. 

 

Yep thats the plan stan