Structural Question

[limerockconstruction]

I'm building a reasonably large extension for someone at the moment and wondered if someone could offer an opinion.

We have a door (900) situated next to a window (1800) so the structural opening is naturally (2700) with a panel of block/brickwork coming up under the window.

The Engineer forgot to specify anything for this opening and naturally I thought that 2.7m was OK for a heavy duty catnic type lintel. However, thought i'd check with him, and true to form he's gone steel crazy and said we have to use UB's and install a wind post on the end of the blockwork nib up under the steel.

I'm only a builder but thought this all seemed way over the top.

The loading above (apologise for the lack of technicality), is 2 skins of thermalite blockwork, with a slate hanging tile detail to the external elevation. A traditional cut roof on top.

If you need any more info let me know.

Thoughts appreciated.

 

[^woody^]

A lintel is fine. The load is negligible in the scheme of things.

Lets just wait for someone to shout "WIND LOADS"

The engineer is over specifying to cover his own backside, but what can you do in real terms? Get another engineer, ask the engineer to provide calcs for checking? Probably nothing

But it is the poor client who ends up paying for it all

 

[tony1851]

If the brickwork returns at each end are minimal, watch out for WIND LOADS!!!!

 

[limerockconstruction]

Thanks Guys.

Certainly very good at one end, and the other end where the window is the panel is c2.2 but the return up the side of the window is only 550 wide but this is for only675mm

Do we really need a wind post - i've never done this before?!

 

[^woody^]

Do we really need a wind post - i've never done this before?!

I look at it this way ... how many windposts were used/specified in this type of work 10/20/30/40 years ago? How many older buildings have fallen down because of lack of windposts?

I'd never heard of windposts 20 years ago, and it is only over the past few years when I am seeing more and more drawings and calculations for these.

Is it global warming making the UK more windy? Or do we have clueless engineers designing things nowadays?

 

[tony1851]

[Or do we have clueless engineers designing things nowadays?

Seriously, it's not clueless engineers. It's engineers creating work for themselves. Whilst wary of windloading from experience, I would agree that in this case the OP's returns are reasonable enough to provide adequate lateral stability.

It's easier to look up a Catnic from their catalogue, but gives the SE hardly any work to do, so he can't charge very much. But a beam and windposts plus connections add up to quite a few pages of calcs., = £££.

In short, you don't need calcs or, indeed, a steel beam for this. And as for windposts?.....

 

[RonnyRaygun]

You mean you've got effectively a pier 675mm high by 550mm deep, but becomes deeper under the window? Cavity or solid wall? It seems unlikely you would need a windpost in that location.

Wind posts are usually used on brick infill panels on framed buildings. They can be used in load bearing masonry buildings where there is a long distance between returns.

 

[limerockconstruction]

You mean you've got effectively a pier 675mm high by 550mm deep, but becomes deeper under the window? Cavity or solid wall? It seems unlikely you would need a windpost in that location.

Yep thats right, and yes much deeper under the window and its cavity brick/blockwork.

I've only recently come across these wind posts - they were on a building we were asked to look at for Bristol Water - I found it odd they were wind posts as the building we were asked to build was inside another building!

 

[^woody^]

Seriously, it's not clueless engineers.

The are clueless if they have not got a clue about other design options, or can not calculate a masonry loading scenario without resorting to over design

 

[tony1851]

Seriously, it's not clueless engineers.

The are clueless if they have not got a clue about other design options, or can not calculate a masonry loading scenario without resorting to over design

Perhaps your wording should be changed from "..can not calculate..." to "....will not calculate..,".
My guess here is that some SE is trying to make work for himself by designing something which he/she knows is not necessary. It's fraud.

 

[limerockconstruction]

I'd love to have the audacity to show him this thread!! Would make my day!

 

[^woody^]

Perhaps your wording should be changed from "..can not calculate..." to "....will not calculate..,".
My guess here is that some SE is trying to make work for himself by designing something which he/she knows is not necessary. It's fraud.

I've never met an engineer who creates work for himself to get more money

Over specify, insist on things which are not really necessary, calculate things "to be on the safe side" rather than "will be satisfactory", or design certain things because they can't design other things, yes, but never fraudulently.

Its a no-win situation when they will "recommend" additional design based on their opinion, but I dont think its due to fraud, just due to being clueless (or lazy maybe)

 

[jeds]

The only times I've specified wind posts were once in a façade which had a lot of openings to relatively slender piers and in a shop which was being split into two and the block dividing panels were nearly 5m high. You've got to be careful in that situation because opening the doors on one shop can cause a huge wind pressure imbalance between the two. I've never specified them in domestic a extension but I have specified goalpost design where side returns were very small or non existent.

 

[limerockconstruction]

After a bit of too'ing and fro'ing he's just sent a one liner e-mail saying that 'Standard Catnic Lintels will suffice'

I don't want to be too cynical about it......

 

[tony1851]

After a bit of too'ing and fro'ing he's just sent a one liner e-mail saying that 'Standard Catnic Lintels will suffice'

I don't want to be too cynical about it......

A more lucrative job must have just landed on his desk!