Gable end blockwork question.

[Rishard]

The inner skin of blockwork is often cut to just below the rafter top. Is there any reason it couldn’t be left a little short and cut to the underside of the rafter? In this situation it would allow my cavity insulation to connect to my roof insulation (insulation between rafters) 

 

I could still mount restraint straps to the underside of the rafters however the straps wouldn’t be ‘built in’ and they would need a masonry fixing to the blockwork. 
 

Most of my ceilings are vaulted / cathedral ceilings.

 

 

[Temp]

I can't think of a reason why that wouldn't work.

 

Some drawings show the strap on top of the rafters and fixed to the brickwork not "built in". Perhaps use a strap with a longer vertical section so the fixings are lower down the wall?

 

 

[torre]

  On 22/03/2025 at 08:27, Rishard said:

mount restraint straps to the underside of the rafters

Expand  

I don't think this on its own is a problem, but the end of the strap will still need to fit over the outside of the blockwork . It wouldn't be enough to fix with plugs etc to the inside of the blockwork (if that's what you're intending) - it's the difference between the whole folded area of the strap resisting pull forces versus just two or three plugged screws

 

 if check with building control that they'll be happy with what you're suggesting - it sounds so sensible from an insulating perspective you wonder why it's not the norm?Maybe just a bit harder to build, or maybe the people who think most about insulation would've already gone for a warm pitched roof

 

[Rishard]

In hindsight maybe a warm roof would have been best in this situation. I’m a bit limited with head height on some areas of this build as 2 rooms have low eaves (1.8m) if I was to move over to a warm pitched roof I’d have to lose the height internally. Not entirely out of the question. I may look into my options regarding this. Thinking off the top of my head, I have 200mm rafters which i planed to fill with insulation. If I introduced a purlin mid span I could reduce my rafters down to claw back potentially 75mm from the rafter thickness. 
 

i wonder if I could use a really long straight restraint strap (2m) and bend it down 800m into the cavity for more fixing points and have 1200mm across the underside of my rafters. 

[Mr Punter]

  On 23/03/2025 at 16:33, Rishard said:

i wonder if I could use a really long straight restraint strap (2m) and bend it down 800m into the cavity for more fixing points and have 1200mm across the underside of my rafters. 

Expand  

 

I don't know how that would help.  I thought the gable restraints were mainly to prevent the gable wall collapsing in high winds by providing lateral restraint.

[Rishard]

I guess the further down the fixings the more stability? Once the noggins are all in between the rafters and the blockwork the strap just locks it in place. If the fixings were only in the top block then it had a higher chance of that block becoming lose? If the fixings ran further down the wall into bonded blockwork I guess this would help a bit? 

[DannyT]

So the straps depending on vaulted ceiling or not would run across the bottom of the cable end, some up the cut up and maybe a couple in the middle if it’s a standard truss roof.

They blockwork goes beyond the underside of rafter so that it is sandwiched between the rafter and the strap and can’t move outwards or blown back in.

I have rarely built a cut up with the strap over the top of the rafter. They are normally under the rafter and built in 150mm-200mm below the top of the cuts.

Edited March 23 by DannyT