Do I really, really need a windpost?

[humblenovice]

Hi All,

I know this seems to be a rather evergreen question on here - but I have a dilemma in relation to our house renovation (and the fascinating lives of Structural Engineers).

We are knocking through an internal wall, and have had a qualified SE to come and confirm that there was no beam required to support any load above. However, this SE also then stated that we would need to either leave 550m of a section abutting the exterior wall, or install a windpost, for lateral support. We later had a surveyor round (to measure for windows) who claimed to have considerable experience with structural calculations (but either retired or not an SE), who suggested that this was unnecessary and that the first SE was being over-cautious. We would much prefer to remove the whole of the wall (as architecturally it makes sense for the kitchen layout etc.), but we don't have funds for a whole wind post install.

So now we are looking for a second SE to assess, but I'm a bit concerned that a lot seem to be 'overcautious' with these calculations, and we are going to pay twice for the same ('incomplete'?) advice, and still end up with a mildly flawed finish. So I'd love to hear your opinions please? (I gather @tony1851 seems to be a resident expert here!)

There is a diagram of the ground floor attached to indicate the wall to be removed. All the green walls are cavity walls - the RHS is a 2-storey extension, the LHS is a party wall as we are semi-detached. I'm not sure what other details would be needed, but obviously happy to provide whatever I can!

 

[noseall]

Hi All,

I know this seems to be a rather evergreen question on here - but I have a dilemma in relation to our house renovation (and the fascinating lives of Structural Engineers).

We are knocking through an internal wall, and have had a qualified SE to come and confirm that there was no beam required to support any load above. However, this SE also then stated that we would need to either leave 550m of a section abutting the exterior wall, or install a windpost, for lateral support. We later had a surveyor round (to measure for windows) who claimed to have considerable experience with structural calculations (but either retired or not an SE), who suggested that this was unnecessary and that the first SE was being over-cautious. We would much prefer to remove the whole of the wall (as architecturally it makes sense for the kitchen layout etc.), but we don't have funds for a whole wind post install.

So now we are looking for a second SE to assess, but I'm a bit concerned that a lot seem to be 'overcautious' with these calculations, and we are going to pay twice for the same ('incomplete'?) advice, and still end up with a mildly flawed finish. So I'd love to hear your opinions please? (I gather @tony1851 seems to be a resident expert here!)

There is a diagram of the ground floor attached to indicate the wall to be removed. All the green walls are cavity walls - the RHS is a 2-storey extension, the LHS is a party wall as we are semi-detached. I'm not sure what other details would be needed, but obviously happy to provide whatever I can!

We have a job in the summer whereby the masonry piers (between openings) we will be building, require stability wind posts (Ancon) building in.

 

[stevie888]

Trust a double glazing guy or an SE? Hmmmm.

Nobody on a forum can give you a definitive answer, and at the end of the day the only opinion that matters is BC when they check the proposals

 

[^woody^]

Houses with no corner returns were all the rage for about 1000 years, right up until the mid 1980's when some bloke (probably a shrewd engineer) invented Wind Posts, and the rest is history.

I've yet to see or hear of any of the millions of houses lacking this apparently essential 550mm of brick work, actually fall down. However, I must admit that I have slyly placed my spaniel's basket in the room facing such a non-compliant corner of my old house, and he will hopefully bark his head off at the sound of any cracking during the night.

The only issue I'm aware of with corners with no wall return and a window right into the corner, is that there is no space for the curtains to hang at the side of the window, and it's a bit annoying.

 

[Ivor Windybottom]

The window fitter "surveyor" probably doesn't know or care about the concept and has got away with it, as he normally just replaces existing windows so doesn't get involved with structural issues. Many houses have suffered from issues due to wood windows being replaced by plastic without their "surveyor" appreciating that the stronger wooden window frame was actually supporting the wall, which cracks after. Don't rely on a window fitter's advice.

I've seen lots of old houses with a similar scenario - basically any room that has more than one window on one face has this situation.

I'm sure they never bothered caring in the past. But it sounds like a very sensible precaution to me. If you've ever knocked a wall down then you'll know that the sort of thing you'd be left with could be pushed over pretty easily with little more than a heavy lean. Once you start swinging opening windows and doors off that then it may not collapse into rubble but you could get some ugly cracks.

Mortar isn't a glue, especially not after a decade or so. It's just a filler to let bricks sit together without gaps. The strength of a wall comes from its shape.

 

[Deluks]

If it were my house, I'd err on the side of caution.
We get seasonal movement cracks on one of our walls, whether or not that's related to a previous owner installing a window 3 inches from an external corner can't be proven.

 

[tony1851]

The old wind-post hobby horse wheeled out again by some SEs.

The distance between the party wall and the original side wall of the house seems to be around 5m, which is not excessive for a horizontal span, and IMO no post would be needed, assuming the house is in a sheltered/suburban area and not on the top of Ben Nevis.

As it seems the first floor joists run onto the rear wall(?), they will also provide some lateral restraint to said wall.

 

[noseall]

Houses with no corner returns were all the rage for about 1000 years, right up until the mid 1980's when some bloke (probably a shrewd engineer) invented Wind Posts, and the rest is history.

I've yet to see or hear of any of the millions of houses lacking this apparently essential 550mm of brick work, actually fall down. However, I must admit that I have slyly placed my spaniel's basket in the room facing such a non-compliant corner of my old house, and he will hopefully bark his head off at the sound of any cracking during the night.

The only issue I'm aware of with corners with no wall return and a window right into the corner, is that there is no space for the curtains to hang at the side of the window, and it's a bit annoying.

I'd never heard of a wind-post up till about 15 years ago. Now we fit them with regularity. Our latest job we have been instructed to fit two proprietary Ancon wind-posts into some blockwork.

 

[humblenovice]

Thank you all for your considered replies. I'll reply in reverse order;

Yes the first floor joists run onto the rear wall, the span is ~5m and we live in a suburban sheltered area.

To be fair to the 'window surveyor/double glazing guy', in previous roles he had designed/engineered calculations for substantial buildings (stadiums, conference centres) and I would find it unusual that he did not know or care about the concept of wind-loading/lateral stability. It wasn't really his current job that I was going off!

However, my partners (entirely sensible I should add) view is that we should not be knocking it all down without a registered/qualified? SE confirming it is not required - which leads me to a simple conclusion;

How would we find one that agrees with this assessment? Presumably if we ask for calculations all SE's should provide the same answer?

It sounds to me like I could go through at least 10 SE's before I find one that suggests we don't need a retaining nib.

As an aside, would knocking this wall through require BC approval? Does it matter if it's completed by a 'competent' person?

 

[noseall]

Thank you all for your considered replies. I'll reply in reverse order;

Yes the first floor joists run onto the rear wall, the span is ~5m and we live in a suburban sheltered area.

To be fair to the 'window surveyor/double glazing guy', in previous roles he had designed/engineered calculations for substantial buildings (stadiums, conference centres) and I would find it unusual that he did not know or care about the concept of wind-loading/lateral stability. It wasn't really his current job that I was going off!

However, my partners (entirely sensible I should add) view is that we should not be knocking it all down without a registered/qualified? SE confirming it is not required - which leads me to a simple conclusion;

How would we find one that agrees with this assessment? Presumably if we ask for calculations all SE's should provide the same answer?

It sounds to me like I could go through at least 10 SE's before I find one that suggests we don't need a retaining nib.

As an aside, would knocking this wall through require BC approval? Does it matter if it's completed by a 'competent' person?

The pragmatism of SE's is directly related to their P.I. payments/coverage. The old sages used to be more 'flexible' than their younger counterparts.

 

[tony1851]

Your first problem is, as Nose pointed out, SEs - particularly inexperienced ones - will opt for the wind-post in order to cover themselves completely, being mindful of their PI insurance.

So from their point of view, why should they do some rather more complex wind-load calcs taking time, when they could choose a big piece of steel, punch numbers into a spreadsheet to prove 'it works', and charge £££s for ten minutes work?

The second issue is Building Control and their inspectors, who are not usually competent to pronounce on strictly structural matters. If you tell them you are removing a wall 'which you have been told is not loadbearing', they might tell you it doesn't need a Building Regs application, and you're back to square one.

As you know the issues, you could try telling an SE what you want (ie to prove there is no problem with not having a windpost) and see if they are able to come up with the proof. You could then submit the figures to Building Control, who would then be bound to accept your application, check the figures, and give you the Certificate of Completion once the work is done.

(With regard to the builder, the recent change to the law under the Building Safety Act requires any builder to be 'competent'. They don't have to be a member of any trade organization, but must have the 'skills, knowledge, experience and behaviours' of anyone expected to do such work. They now have to sign a declaration to that effect on completion, as does an SE or any other designer/professional who might be involved).

A bit of a chicken-and-egg situation.

 

[Ivor Windybottom]

You seem to already know you're going against the grain by expecting anyone qualified to agree that you don't need one. You could end up spending a lot more on reports than it would cost to add one, then still end up with a cracked wall when you later find out they were right anyway.

Building control is there to protect you. You shouldn't go out of your way to circumvent it, then you're being your own cowboy builder. Personally I'm not usually worried about getting all the official paperwork for DIY jobs, but at least make sure it complies with the standards.

I believe they can be added after removing just one of the two skins of the wall. It would probably make most sense to remove/replace the inner skin, leaving the outer untouched and unscarred. You'll be making a right mess removing the wall anyway, a bit more demolition and rebuilding shouldn't be the end of the world.

 

[Deluks]

To be fair to the 'window surveyor/double glazing guy', in previous roles he had designed/engineered calculations for substantial buildings (stadiums, conference centres) and I would find it unusual that he did not know or care about the concept of wind-loading/lateral stability. It wasn't really his current job that I was going off!

Double glazing salesmen will give you any old bunny.

 

[Ivor Windybottom]

To be fair to the 'window surveyor/double glazing guy', in previous roles he had designed/engineered calculations for substantial buildings (stadiums, conference centres) and I would find it unusual that he did not know or care about the concept of wind-loading/lateral stability. It wasn't really his current job that I was going off!

Is this what he told you? If this wasn't bull then I'd expect him to be designing great public buildings, not measuring up for windows.

It's disturbing just how good some people are at lying. They can look you in the eye and not care that they're spouting cobblers.