Screw type for ridge abutment metal straps.

[epsilonGreedy]

Before I move onto slating a small section of roof I need fix two long metal restraint straps under the ridge to reduce the risk of the ridge & truss flexing away from the abutment wall. There will be code 3 or 4 lead soakers above and don't want these to tear.

 

The roof is small 4.25m x 3.1m eave to eave, 30 degree pitch and has two hips opposing the ridge abutment. I mention this to illustrate the forces involved are not great.

 

It is fortunate that my brickie switched from 8kg light blocks to facing bricks well below the eventual truss ridge height so I can screw the metal straps to bricks rather than light blocks. Having read up on options for masonry fixings I reckon my options are:

 

1. Masonry screws that self tap a thread after a large pilot hole is pre drilled.
2. Fix in a threaded stud with resin and attach the metal strap. 

 

The straps are 1.4m long and will span 3 trusses, at the wall end there 3 fixing holes.

[Big Jimbo]

For me i would use Two of the holes, with resin fixed...I love a bit of resin.

[epsilonGreedy]

14 minutes ago, Big Jimbo said:

For me i would use Two of the holes, with resin fixed...I love a bit of resin.

 

 

Thanks. I had previously steered away from resin fixes because I thought these involved manually mixing up a pot of resin plus hardener. Watching a video the other day I discovered the industry has invented standard cartridges that mix the two components as the resin is squeezed out of the cartridge. Creating a dust free drilled hole looks key to a successful fix.

[Big Jimbo]

Good dust free hole, and it works brilliantly.

[markc]

23 minutes ago, epsilonGreedy said:

 

Thanks. I had previously steered away from resin fixes because I thought these involved manually mixing up a pot of resin plus hardener. Watching a video the other day I discovered the industry has invented standard cartridges that mix the two components as the resin is squeezed out of the cartridge. Creating a dust free drilled hole looks key to a successful fix.

As big Jimbo said, clean dust free hole is the secret, also (If possible) use a drill in reverse to push the fixings in - the thread then tries to force the resin back into the hole and ensures it is forced into the masonry or concrete pores/cavities and fixing threads, something we learned while installing thousands of them on big construction projects.

Edited February 25, 2021 by markc

[epsilonGreedy]

25 minutes ago, markc said:

As big Jimbo said, clean dust free hole is the secret, also (If possible) use a drill in reverse to push the fixings in - the thread then tries to force the resin back into the hole and ensures it is forced into the masonry or concrete pores/cavities and fixing threads, something we learned while installing thousands of them on big construction projects.

 

 

Thanks. Is there a minimum stud diameter below which resin fixing is problematic? I think the screw holes in the strap are 5mm or 6mm.

[markc]

41 minutes ago, epsilonGreedy said:

 

Thanks. Is there a minimum stud diameter below which resin fixing is problematic? I think the screw holes in the strap are 5mm or 6mm.

Yes, 6mm studding into 8mm hole is about as small as you can go or the resin nozzle wont go into the hole far enough to pump it in and let the air out