doubling up floor joists

[nelliedee]

Hi
We are about to put in the 1st floor joists on a 2 story extension.
On the plans it shows an area (where new stairs will pass thru) that requires double and treble joists.
Question 1; do we use 2 joist hangers side by side for each joist or do we use 1 joist hanger and bolt the second joist to the supported joist.

Also we need to place a small piece of joist (trimmer) between main joists, do we hang this using joist hangers that hang off the joist sideways (90 degree)
Thanks
Nelliedee

 

[freddiemercurystwin]

Question 1; do we use 2 joist hangers side by side for each joist or do we use 1 joist hanger and bolt the second joist to the supported joist.

No, use 1 joist hanger that's wide enough for 2 or 3 joists. By the way all double or treble joists should be bolted together all along their length.

Also we need to place a small piece of joist (trimmer) between main joists, do we hang this using joist hangers that hang off the joist sideways (90 degree)

Yes

 

[nelliedee]

Thanks
Any tips on where to buy the Hangers wide enough to take 2 or 3 joists?


Also if the joist span is 3.5 Metres, how many bolts would you use to bolt the double/treble joists and are there specific bolts we should use?
Nelliedee

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[freddiemercurystwin]

Any tips on where to buy the Hangers wide enough to take 2 or 3 joists?

Any builders merchants would stock them I'd think

Also if the joist span is 3.5 Metres, how many bolts would you use to bolt the double/treble joists and are there specific bolts we should use?
Nelliedee

http://www.nhbcbuilder.co.uk/NHBCpublications/LiteratureLibrary/Technical/filedownload,21418,en.pdf see page 5, in the absence of anything detailed on your drawings run this by building control to make sure he's happy before you bolt them together. Use M12 galv studding (or bolts if you can't be bothered to saw them) with plate washers ( http://www.topfix.co.uk/images/products/miscell_platewashers.jpg ) and personally I'd use lock washers too.