Strongtie Joist hangar query

[shd1970]

I'm planning to use JHA270/47 hangers for the joists for my flat roof garage frame, fastened with twist nails :

https://www.strongtie.co.uk/products/detail/joist-hanger-with-adjustable-height-strap/769

As the garage is link detached, the hangers will be attached to 120x47mm header on each side, bolted to each house

My question is, as the total length of the hanger is 236mm but the header is 120mm, can i trim the legs of the hanger and nail to the front and top only of the header, or should i unbolt and fit it down the back also ?

 

[Deleted member 174758]

Ideally you should always wrap and extra length over the top and down the back and nail in every hole if at all feasible.

 

[shd1970]

Ideally you should always wrap and extra length over the top and down the back and nail in every hole if at all feasible.

Thanks Job for the reply

You say is at all possible. For a flat garage roof, do you think it would be any problem to trim them down as as mentioned, the header will be bolted to a wall ?
I know its not ideal but its a garage roof so will only be used for foot traffic for maintenance, and when the roofers felt it and there doesn't seem to be any 47mm x 120mm hangers that i can find anywhere

 

[^woody^]

You can use the bottom part of deep hangers, but that one you linked to would not be suitable as the bottom 100mm or so has no fixings to whatever you plan to fix it to.

Can't you find some better ones with a deeper fixing plate area?

 

[shd1970]

Thanks woody but unfortunately no, not managed to find any yet

Is 50mm the new modern day norm for timber widths instead of 47mm, or is there some other difference as I notice 50mm hangers seem more readily available

 

[BigJock2005]

Thanks woody but unfortunately no, not managed to find any yet

Is 50mm the new modern day norm for timber widths instead of 47mm, or is there some other difference as I notice 50mm hangers seem more readily available

I’d love to know where 47mm comes from. It’s not a 2x4 because that would be 51mm wide. Is it a European thing? 47mm is close to 1 7/8” so maybe that’s it. Anyhoo it’s a pain in the arse.

 

[Deleted member 174758]

47mm is what you end up with after sawing down to 2in (50.8mm) then kilning, methinks The "3in" (76.2mm) nominal stock we are currently working with is actually 71 to 73mm thick. A "2 x 4", or in UK parlance an ex-4 x 2 is actually slightly smaller in sawn kilned structural grades like C16 and C24, more like 97 x 47. If the timber is "regularised" (aka CLS) it is slightly smaller again, circa 90 x 44mm because all the faces (and edges) have been machined after kilnin

In mainland Europe they start metric so my experience over there was that the sizes tend to vary a wee bit depending on the timber species and country of origin

 

[cdbe]

 

[oldbutnotdead]

What size joists you using? Can't see any dimensions for the BPC hangars I usually use (43424 from the same supplier as above) but they appear to have more nail holes in the first 100mm than those posh ones you linked to, with your setup you can't spike the back cos there's a wall in the way. Those 20088s linked above- be handy if they specified what a heavy duty load was for double the cost!

And timber dimensions- grrr. Last batch of 4 x 2 I bought is more like 45 x 95 which is a pain when you have to stuff 100mm rigid insulation in.

 

[shd1970]

View attachment 193591

thanks cdbe

i saw those but has scrubbed them as they are 97mm high and i'm using 120mm
from the picture, there is no place to fasten on approx the bottom 3rd meaning likely only 60mm would be able to be fastened
That said, i'll head over to BPC to see if they have a diagram with measurements on

they may be the best of a relatively small list to choose from

 

[shd1970]

What size joists you using? Can't see any dimensions for the BPC hangars I usually use (43424 from the same supplier as above) but they appear to have more nail holes in the first 100mm than those posh ones you linked to, with your setup you can't spike the back cos there's a wall in the way. Those 20088s linked above- be handy if they specified what a heavy duty load was for double the cost!

And timber dimensions- grrr. Last batch of 4 x 2 I bought is more like 45 x 95 which is a pain when you have to stuff 100mm rigid insulation in.

thanks obnd

120mm x 47mm is what i have currently and i'm hoping to source the same as i'm extending my flat roof garage forward
that said, it seems that what the timber merchants bring is what you get and then you have to hope you can get the joist hangers to fit

i'll buzz them to see if i can get accurate dimensions

 

[^woody^]

Can't you save yourself a lot of bother and just lower the plates and rest the joists on them without hangers?

Or fit masonry hangers.

 

[shd1970]

unfortunately not Woody, as there is a side door that the header will then cover slightly, and additionally, the fascia board would then be double the height if i'm understanding correctly, which i don't want