When do you need windposts?

[davidmiller]

Hello. Is there a particular regulation or rule of thumb for when windposts are required. I've never had to do them but maybe they are commonplace in domestic extensions these days?
Thanks if you can help.

 

[^woody^]

When a structural engineer says so, normally.

 

[tony1851]

Do you mean a goal-post when taking out a wall?

If so, architects often specify them but don't really know why; the SE then punches a few numbers into his spreadsheet and comes up with a frame which could support the Empire State building - but can't tell you whether or not it's necessary. The council's checking engineer gazes bored at the reams of figures and diagrams of parabolas and just stamps them "approved" so that he can get back to his coffee and Kit Kat. The builder then builds it, but doesn't know why he has to. The Building Inspector sees it, is impressed by the bolting and welding, but doesn't understand it. The client assumes it's vital because he's paid ££££s for it.

Fact is, few even bother to determine if a w/post is actually necessary; strange - because in 9 out of 10 cases it just isn't.

 

[davidmiller]

Thanks gents.
Yes I think over specification might be the case. All I know is about 19 years ago even working on blocks of flats I never saw one.
I assume they are more common in masonry than timber?
I've done a bit of research online. (This is for new build). It doesn't seem too much of a tricky job, maybe getting it in the foundations will be.
I cant find out how much they cost online. I suppose that could be the main rub.

 

[mrrusty]

Do you mean a goal-post when taking out a wall?

I think possibly supports to provide lateral restrain to masonry panels - e.g. gable ends?

 

[davidmiller]

Do you mean a goal-post when taking out a wall?

Sorry I missed this question.

No its because the wall is apparently too long on a extension. Thats why I as wondering if theres a set rule when to use a post. like there is with expansion joints.

 

[tony1851]

Ah, I follow now.

How long is the unsupported length of the wall, and how high is it (single- or double-storey?).

There's no regulation as such, though the Approved Document A (structure) stipulates maximum lengths, heights and thicknesses of certain walls if they are to be regarded as 'deemed to satisfy'(can't remember them at the moment). If you go outside those parameters, presumably Building Control could ask for figures to justify, or then use windposts within the cavity. There would of course need to be some rigid structure to fix the top and bottom of the posts.

 

[tony1851]

I cant find out how much they cost online. I suppose that could be the main rub.

Ancon do a stainless steel system but IIRC it's purpose-made to order, probably ££££££s :<(

 

[davidmiller]

How long is the unsupported length of the wall, and how high is it (single- or double-storey?).

Iv'e hopeully attached a sketch to sum up better than I could explain. I'd like to think its pretty well tied in by the internal walls. Ive put a question mark where there wont be a internal pillar so that might leave too long of a run. But hopefully the wall above would help?