Has anyone any experience of installing a suspended timber floor into
a new building / extension ? I understand that according to UK
building regulations, new joists have to be tied into the new wall
using galvanised restraining straps at max 2000 centres and these have
to be taken over at least 3 joists with tight packing between. I also
understand that this is normally achieved using what is in effect an
'L' shaped strap with the short edged pulled up tightly behind and
built into the block wall and the longer end secured on the top of
All well and good, but what can you do if the top of the joist doesn't
align with the horizontal mortar beds in the block wall ? Can they
be installed on the bottom of the joist ?
What if it still doesn't align, is there some other method to achieve
the same thing ? I have been wondering about the possibilty of
obtaining a strap which can be intalled in a vertical mortar gap with
a bend to pull it up against the back of the block and then a twist at
the front of the block so it still sits on top of the joist.
Does any of this make any sense to anybody?
Use appropriately sized joist hangers then your joists will align with the
mortar joints. Should this not be possible use a smaller block one course
below. The strap must go over an uncut block. It can be fastened either
above or below the joist and noggins. The gap between the last joist and
wall needs suitable packing.
Thanks for the advice, joist hangers aren't actually going to help
as I am actually talking about an extension and the new joists need to
align with the top of the existing joists in the house otherwise there
will be a difference in floor level. I should be able to work
something out with cut blocks in order to bring the mortar beds in
Are my thoughts on a twisted bent strap impractical then ?
The hangers give you the opportunity to fine tune the floor height (packing
No, I thought you were spot on. The requirement is the strap must be of
durable metal, 30mm x 5mm minimum section, spanning 3 joists. Bang the
noggins in between the joists and run the strap above or below these and
then over a _full_ block. Although I can't see any written guidance, I
believe the bend should always be downward rather than upward.
Good link thanks. I got the impression he was talking about the straps
that are set in the gable to stop the roof blowing away.
It does happen that when the bricklayers don't know what they are
doing, or don't care, that the courses run out of level. If it's a new
house you can insist that the builder put it right. Take some
litigation that though. Renovations are bound to hit that snag as
buildings settle. The trick there is to notch the joists to suit.
It is the thickness of the joist at the centre that is crucial so you
might get away with quite deep notches at the ends. You can always
underpin them with a cross member at the wall? Or notch the joists to
go over a 3"x 2" at either end fixed to the wall securely?
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