• We invite you to join UKWorkshop.
    Members can turn off viewing Ads!

Joist hangers for rafters causing 3 issues

UKworkshop.co.uk

Help Support UKworkshop.co.uk:

porridgebear

Member
Joined
8 Apr 2021
Messages
13
Reaction score
1
Location
London
Hey everyone,

So with my shed/garden room build I got the rafters up, birds mouths-n-all (that was a pain) and I decided to use some joist hangers upside down to lock them to the double top plate of the frame (back and front side).

This has caused a couple of issues and I am wondering if it's worth just not bothering and using 3 sets of noggins to lock to the frame + toe nailing.
  1. The joist hangers have long tails that come down the vertical against the stud work and the thickness of the hangers would mean plywood wall against the frame would not sit flush
  2. The joist hangers also do the same where they strap over the top of the rafters - worse in fact as they bend in an arch - I tried to hammer them down but still when I tried the ply roof it doesn't sit flush to the rafters.
  3. PIR insulation on the inside cannot slot across to the top of the top plates - they get blocked by the hangers so you get an air cap which would be closed with ply wall/ceiling but still it doesn't seem ideal
So yeah - I am considering doing away with them for the upside of not having these issues. Then I am just left with securing the rafters as well - I am thinking either a noggin set along each plate OR maybe there is some L bend hardware to keep them down more to the front of the top plates (to solve (3) above)

Anyway, just wondered what people thought about NOT using joist hangers in this way.

Cheers!
 

Jacob

Pint of bass, porkpie, and packet of crisps please
Joined
7 Jul 2010
Messages
18,931
Reaction score
1,026
Location
Derbyshire
Sounds a but complicated! Why use joist hangers - if you've got a birdsmouth it just needs one nail through, or 2 skewed. Just to pin the rafter in place, not really structural. They don't need holding down much unless you are expecting the roof to blow off!
 

porridgebear

Member
Joined
8 Apr 2021
Messages
13
Reaction score
1
Location
London
Sounds a but complicated! Why use joist hangers - if you've got a birdsmouth it just needs one nail through, or 2 skewed. Just to pin the rafter in place, not really structural. They don't need holding down much unless you are expecting the roof to blow off!
I am inclined to complexity and detail, I am getting the sense I have overdone my "shed" - still, all good learning lol. OK well I am encouraged by your response that I can indeed do away with these annoyances.
 

scooby

Established Member
Joined
23 Mar 2006
Messages
794
Reaction score
130
Location
Greater Manchester
Two appropriately sized nails skewed through the rafter into the wall plate will be enough. I don't see any need for the hangers.
 

Fergie 307

Established Member
Joined
28 Dec 2019
Messages
443
Reaction score
221
Location
Sandy Bedfordshire
If the framing allows you to access underneath the top plate then I have used Wirox mushroom head fixings before, passing through the top plate from underneath and screwing into the joist, very solid and neat.
 

Woody2Shoes

Impressive Member
Joined
5 Jan 2015
Messages
1,981
Reaction score
307
Location
Sussex UK
Sounds a but complicated! Why use joist hangers - if you've got a birdsmouth it just needs one nail through, or 2 skewed. Just to pin the rafter in place, not really structural. They don't need holding down much unless you are expecting the roof to blow off!
Jacob's right.

e.g. https://cdn.h2ouse.org/wp-content/uploads/birdsmouth-cut-rafter.jpg

His point about the roof blowing off is adressed (in the building regs) by installation of restraint/tie straps at suitable spacings.
e.g. Light Engineered Restraint Strap
 
Top