Which joist hanger fixings for flat roof extension?

[kevsterdiy]

Hi.

I'm looking to extend my garage flat roof.
It's a single garage, attached to house one side. Attached to neighbours garage the other side. The roofs arn't attached because of an 8 inch step in ground level.

The current construction of the roof timbers as built in 1976 are:

- a length of 4x2 inch (100x50mm) down both side walls at a slight slope towards gutter end. Fixed to the wall by huge taper nails (the name escapes me)
- on top of this cross joists of 5x1.5 inch (125x38mm) at 600 centres span across the width with one nail at 45 degree in each end of each holding it down. Yep that's all.
- then finally length ways 6x1 in (150x25mm) boards with felt on top

Probably not to regs then or now...... but it's still standing!

My plan, extended the garage by 2.8meters on the gutter end, to full house depth. Neighbours current fence becomes a single course brick wall.

For the new timber use either 50x125 or 50x150 at 600 or 400 centres with face fix joist hangers to fix to the walls. Board as original or 25mm marine ply board.

Like this, 50 wide by 100-150 deep:

https://www.metrofixings.co.uk/main/product/productinfo/14350/1
https://www.orbitalfasteners.co.uk/...ae-heavy-duty-u-hanger-galvanised-sae380-50-2

I'm confused by the best method for fixing. Different websites for the same Simpson product says use:

- expanding bolt fixings with or without resin
- square twist nails 30/40 long in all holes
- concrete/masonry screws

Probably all are better than how the builders did it but I don't really want to be smashing the he'll out of a new wall or indeed the house or drilling massive holes for bolt fixings.

I prefer the concrete screw method, would this be suitable?
http://www.screwfix.com/p/easydrive...77babe0a768e&gclid=CObDgOHlm80CFbYV0wod-rcAzw
In all holes (except large holes) in the bracket to the wall?

Then what is the best method to fix the timber, normal nails, twist nails or screws?

Finally I am tempted whole I am at it, cut a way the original 4x2 side supports (bit at a time) and replace it with the same joist hangers on each cross beam.

Thanks for reading. Any help appricated.
Kevin.

 

[Deleted member 174758]

If your garage wall is single skin brick then you'll possibly struggle to get a face fixing into it through a joist hanger because of the thinness of the masonry (and the risk of blow-out on the other side). Accuracy will also be an issue IMHO. You'll also need to be careful how close to the top of the masonry you drill because bricks can and do split when you drill near the edges. Personally I'd be looking at using a wall plate fixed to the upper face of the wall and having my hangers attached (nailed with twist nails) onto that. Depending on where you live I'd also consider whether or not I need to have some form of tie strap between the rooh structure and the masonry to resist high winds

 

[kevsterdiy]

If your garage wall is single skin brick then you'll possibly struggle to get a face fixing into it through a joist hanger because of the thinness of the masonry (and the risk of blow-out on the other side). Accuracy will also be an issue IMHO. You'll also need to be careful how close to the top of the masonry you drill because bricks can and do split when you drill near the edges. Personally I'd be looking at using a wall plate fixed to the upper face of the wall and having my hangers attached (nailed with twist nails) onto that. Depending on where you live I'd also consider whether or not I need to have some form of tie strap between the rooh structure and the masonry to resist high winds

Thanks for your reply. Yes I agree any fixings of the bolt type for direct wall face fix of joist hangers or a timber wall plate fixed high up runs the risk (almost certain) of breaking the bricks, as well as depths of the bolts.

Complicated by the fact that in have 34mm drop on the new section of roof. Plus any height difference to the nearest course of bricks.

1) I'm not quite sure what you mean by fixing a wall plate to the upper face, so it's lower on the wall, do you mean the top, and how?

2) Not a masonry hanger that folds over the top and is supposed to have further masonry above?

I understand then timber to timber joist hangers from wall plate to joists on this wall plate.

I have looked at a relatives garage, typically it has the fall sideways rather than longways and it was created by wedges/furrings on top of the sideways joists.

However what caught my eye was the joists sit on the wall, flush to the outside with a facia on the end. Held down only by two twisted metal ties.

Tried to apply this method of design to my roof and becomes a stubbing block with trying to again allow for the fall angle and the nearest height in course of bricks. Could end up cutting wedges of bricks or blocks and mortar to achieve the angled top of wall to then sit joists on.

Granted I'm not a roofer or bricky but I can normally see a method or way.

Every flat roof built on garages on my estate has the same construction, and would have the same issue doing the same. Just thrown together with big nails was the regs then!!!

 

[kevsterdiy]

Could I instead bed a joist on top of the wall on mortar (ie brick 2 courses less along the side) Use this as a wall plate to fix joists to with hangers.
Bed either horizontal or at the angle of the roof fall. Depending if the cross joists are 90 deg to the fall angle or not (they are on existing garage)
Then tie this wall plate down with the long twisted ties.....?
Facia board would be on the outside of the wall plate.

 

[kevsterdiy]

JobAndKnock, any explanation of your suggestion would be wonderful. No one else seems to have any ideas. Thanks