Rafter to ledger board connection.

[John2000]

Hello 

I want to fix my rafters to a ledger board. I’ve made a small bird mouth cut to seat the rafter onto ledger. This has the full 47mm bearing. Trouble is I’m looking at code complaint way to fix these without nailing or screwing too close to the limits. This is the diameter of the fixings within the distances of the end grain, edges, birds mouth angle etc. due to the rafter sitting high on the ledger I haven’t got an option to skew nail through the plumb (heel) cut. If I go in through the sides and down into the ledger  I’ll be too close to the birdmouth angle. I was thinking either pre-drill and go in with a long screw from the top. 5mm directly down so it lands 25mm in the centre of the seat and into the ledger. Or use some kind of twisted restraint bar along the side of the rafter and twist to then hit the ledger. 

 

The downward thrust is taken care of by the wood to wood seat. It’s just uplift and connection. I’m assuming horizontal twist - although I can noggin in between to stop this twist and slide. 

 

Anyone with any firm knowledge on this situation please help. 

 

(Also - please don’t reply if you’re just going to say plumb cut with a hanger, etc) it needs the bird mouth for BCO.)

 

Many thanks. Picture below. 
 

 

[Mr Punter]

Truss clips to prevent uplift, noggins to prevent twisting.

[Russell griffiths]

There’s a mini hanger called either a TRIPLE GRIP or MULTI GRIP it’s a small metal plate with a cut in it that can be used in many ways, but by bending it with a hammer you can get 3 fixing points out of it, hence why I call them triple grips. 
they are about £1.50 each. 
fix with twist nails. 

[Nickfromwales]

 

Be sure to use the right screws if you don’t use twist nails, as BCO will fail you otherwise. 

[saveasteading]

It is also stabilising the walls, linking them and stiffening the whole structure.

Not being a timber frame expert I was surprised to find out that twist nails were the expected fixing and widely available. Our joiners knew this and were happy.

They are clearly fast and easy to fix.

That's for experienced joiners... a mouthful of nails, tap tap wham.  I'd be very slow.

 

But if you haven't room to swing the hammer then screws are fine but do get either a spec from a designer  or approval from bco.  The twist is to prevent pull-out so you'll need a coarse threaded screw. Then you can use a drill and a 90° attachment if necessary.

[Nickfromwales]

7 hours ago, saveasteading said:

It is also stabilising the walls, linking them and stiffening the whole structure.

Not being a timber frame expert I was surprised to find out that twist nails were the expected fixing and widely available. Our joiners knew this and were happy.

They are clearly fast and easy to fix.

That's for experienced joiners... a mouthful of nails, tap tap wham.  I'd be very slow.

 

But if you haven't room to swing the hammer then screws are fine but do get either a spec from a designer  or approval from bco.  The twist is to prevent pull-out so you'll need a coarse threaded screw. Then you can use a drill and a 90° attachment if necessary.

Screws need to be a lesser tensile iirc.