Hanging floor joists

[r.p.mcmurphy]

My brickie says that BCO's prefer joists to be hung of joist hangers these days rather than having them mortared into the walls. why would this be?

steve

[<me9]

Latest building regulations require it. I can think of several good reasons, Rot, Insulation, integrity of walls etc.

[Dave Plowman (News)]

Less chance of moisture penetration?

[Rob Morley]

Because he's trying to make life easier for himself?

[brugnospamsia]

That was my first thought faced with this myself - saves making holes in the walls to get the new joists in ...

Reminds me I really need to involve the BCO at an early stage for my project ...

[John Rumm]

and less chance of penetrating a fire break, or allowing drafts through.

[nafuk]

It's mainly to do with the new (Part L?) regs for insulation. Joist hangers stop thermal bridging. The down side is that the floor will be more susceptible for squeaking. You can set the joists into the walls and use plastic "boots" on the end - this meets the new regs (see Screfix 31310).

[Hugo Nebula]

On Sun, 31 Jul 2005 09:49:53 +0100, a particular chimpanzee named "r.p.mcmurphy" randomly hit the keyboard and produced:

Couple of reasons:

1. If the wall is a party wall, the joists MUST be on hangers to prevent flanking sound transmission from the floor to the wall. Joists built into a masonry wall can also shrink and allow air (and sound) to travel through the wall.
2. It is recommended that all joists are on hangers to external walls to maintain the air-tightness of the building (warm air uses energy to heat, so you don't want it escaping through the walls). I think most BCOs would allow the joists to be built in, provided that they are sealed with mastic to seal any gaps.

[Hugo Nebula]

On Sun, 31 Jul 2005 11:09:27 +0100, a particular chimpanzee named Rob Morley randomly hit the keyboard and produced:

So why do 90% of brickies & joiners still cut pockets in the blocks, and look aghast when you tell them they should have used hangers.

[brugnospamsia]

oops ! - missed that it was _new_build_ ....

I guess most tradesmen are fairly "conservative" ... and it has to be said there are probably millions of houses where it proved to be a perfectly reasonable way to do things ...though I have to say that as I virtually rebuild my Victorian hovel I have good evidence for wishing to avoid having any timber directly in contact with the solid outside walls - it's amazing my house is still standing !