Joists

[The Medway Handyman]

Is there a convention for which way joists run in a house? e.g. Front to back or side to side?

And if the joists in the loft run front to back, would all the others?

[dom]

Whichever is the shortest span.

[Dave H.]

Usually whichever direction gives the shortest and therefore cheapest joists[1], although it's usual to use 'em to tie the wallplates at the top of the front and rear walls (up in the loft) together too, to give a bit more structural strength.

Dave H.

[Roger Mills]

I don't think so! My house - as built - had some going front to back and some going side to side[1].

Joists in the loft of a 'simple' house, with gable ends and the roof sloping down each side from the ridge, are more likely to run front to back - with the bottom ends of the rafters tied into them - or the equivalent with a trussed roof. This doesn't apply to more complex roof designs - such as hipped, or with additional gables at right angles to the main roof. Even in the simple case, I don't think you can deduce much about lower levels from the direction of roof joists.

[1] At one end of the house they're front to back, and then there's an RSJ parallel to these joists - which supports an upstairs dividing wall, and carries one end of the side to side joists at the other end of the house

[Malcolm]

No. In my late 1990s Redrow house joists run side to side (except for one small patch under the en-suite), parallel to the ridge of the roof. I was in the house regularly while it was being built an have the photographic evidence

Malcolm

[sm_jamieson]

Commonly front to back downstairs, with sleeper walls to support the joists and reduce the span. Often across the house on the first floor, using internal walls to reduce the span. And in the loft whatever direction is needed to tie the rafters, usually parallel to the gables. Basically a compromise between shortest span and function. Simon.

[ARWadsworth]

There is no convention. Sometimes the joists change directions between the left/right hand side of a house or the front/back of a house.

Adam

[Dave Plowman (News)]

In London, if a semi or terraced house, they all seem to run front to back. I was told this was for additional fire protection - if they went side to side and into the party wall as of old, there'd be less wall protecting them from fire.

[Tony Bryer]

Traditionally on terrace and semi-detached, front to back, since building joists into party walls was not allowed. Much less the rule since joist hangers came into use.