Wind posts. Is there an alternative?

[flanagaj]

Last structural engineer made no reference to wind posts, but the new SE I employed to come up with a lintel schedule, says that I need them.  Thrown a complete spanner in the works as these were never designed in and I have no idea how you go about fitting them to the slab? Brickies are on site and building up to DPC, do they have to be bolted to the slab?

[ProDave]

My designer originally proposed them.  I took one look at the detail, which added complications to the founds for the wind posts to bolt onto.  And then appeared to compromise the insulation by having a steel goal post built into several of the timber frame sections.

 

I asked for a re think and he came back instead with a standard timber frame, but modified to have two layers of OSB with staggered joints to give the required racking strength instead (normally only 1 layer used)

[Super_Paulie]

pretty sure my post was dropped onto threaded bar on a pad extending from the founds, or at the very least you could just resin bolt them in. Ive had a look and have no photos of it going in, the builders just did it all. You'll have to go back to your SE surely to see how thats meant to go in, as mine was drawn in by them. It is a thermal bridge as its in the cavity and into the inside but its insulated behind it obviously and a strip of aerogel over it on the inside and the thermal camera doesnt pick it up now its all boarded.

[flanagaj]

So basically, I am completely screwed.  The original SE made no mention of them.  Building Control haven't made any comment on the submitted structural calcs and now I am near DPC and don't see how they can possibly be added at such a late date.  

[ProDave]

So what drawings are you working to?

 

What did the original SE specify to give adequate racking strength?

 

Why has the new SE changed that?  Surely he will have provided proper drawings?

[flanagaj]

Just now, ProDave said:

So what drawings are you working to?

 

What did the original SE specify to give adequate racking strength?

 

Why has the new SE changed that?  Surely he will have provided proper drawings?

So I am working to the drawings that were submitted to BC.  To cut a long story short, I used Barrat Associates originally to do the SE calcs for the building regs submission.   3 months ago I got in touch with a local SE to do the design for the staircase and a bit later on, I asked her if she could do a full lintel schdule for me as the previous SE only detailed the large lintels.   It was whilst she was doing this that she commented on the drawings not having any details regarding expansion joints.   As a result I thought it would be a good idea to get her to have a detailed look at the drawings and see what else had not been specified/missed ...

[ProDave]

So go back to SE2 and say you don't want wind posts, ask for her alternative?

[flanagaj]

19 minutes ago, ProDave said:

So go back to SE2 and say you don't want wind posts, ask for her alternative?

That is what I am pushing for.   When she did the spec for the concrete slab, she specified 150mm slab laid on 50mm concrete blinding with two layers of A252 mesh.  Given the ground here is no clay, very flinty soil and then chalk at 1200mm it was massively over engineered.  Especially, considering it was a domestic slab.  

[saveasteading]

Wind posts have large overturning forces so there is a big footing too. So it's too late for that.

Alternatives are racking panels as @ProDave suggests, and the cost and inconvenience are low. Or a structural goalpost utilising the existing structure.

 

Can't comment on why one SE thinks it necessary and another doesn't.

[markc]

Do you have any details? Are they required to prevent racking of the structure or to reduce wind loads on brickwork, glazing etc.

[flanagaj]

9 minutes ago, markc said:

Do you have any details? Are they required to prevent racking of the structure or to reduce wind loads on brickwork, glazing etc.

Wind loading on the brickwork.  Just been speaking with the bricklayer and unless the wind posts can be bolted to the slab, I'll be getting a breaker in to break the blocks/lean cavity fill back to the foundations 😞

[Mr Punter]

There is sometimes quite a lead time on wind posts.  How many have been specified?  Somewhere along the line you will need structural drawings and calcs that comply with part A.  You can normally bolt the windposts to the slab or concrete them in.  They add a surprising amount of strength and stiffness to a wall.

 

The alternative could be some brick reinforcing - like train track in the mortar beds - but I don't know if it will work for your design.

Edited 7 hours ago by Mr Punter

[flanagaj]

17 minutes ago, Mr Punter said:

There is sometimes quite a lead time on wind posts.  How many have been specified?  Somewhere along the line you will need structural drawings and calcs that comply with part A.  You can normally bolt the windposts to the slab or concrete them in.  They add a surprising amount of strength and stiffness to a wall.

 

The alternative could be some brick reinforcing - like train track in the mortar beds - but I don't know if it will work for your design.

I am still waiting for the SE to give me the details.  The bricklayers have said that it's no issue as they can start the build up elsewhere and come back to that section once it's finalised.   It's frustrating that the original SE completely failed to spec them and the new SE specs them right at the last minute.

[Mr Punter]

They can be expensive as well!

[Gone West]

3 hours ago, flanagaj said:

It's frustrating that the original SE completely failed to spec them and the new SE specs them right at the last minute.

What is it that makes you believe the second SE rather than the first SE.