Structural Engineer Required

[Doitproper]

Can anybody help with a practical structural engineer experienced in house design who doesn’t want to over design everything. Looking to remove the end return on a wall that is to be extended – to provide a continuous wall line extending into an extension as shown on the plan. I am sure doing this as a new build would be ok but the Architect says it cant be done without goal posts, structural engineer just says “no” (doesn’t offer a solution), builder says it is complicated and needs structural engineer. None of them give any reason apart from this is what we have to do nowadays. Similarly, the structural engineers I’m contacting want to put in a wind post where the new wall starts but appears (in my mind) to be superfluous for a 6m long wall.

Would be looking for either a calculation or note demonstrating it complies with the relevant codes ie Document A to confirm to the BCO that its ok. I understood that a cavity wall can be around 9m long without lateral supports. Total length of the wall without buttresses will be 6.17 from a chimney breast. The extension will have a flat (warm) roof with 2 layers 18mm OSB which should be able to resist any racking forces.

I realise there are circumstances when it cant be done ie a long extension on a wall without any intermediate wall / chimney offering lateral support or vaulted roof extension. Personally I’m not concerned as the wall is less than 3m away from the neighbour so wont be exposed to the full brunt of the wind (but accept he could demolish or have his house demolished !).

There will be a structural beam (spanning between A & C) resting on the wall (with a reaction of around 25 kN). This beam supports the wall of a new dormer above and the roof joists for the extension but I would expect this extra load to increase wall stability on account the extra load will reduce tensile forces in the brickwork.

The property is just north of Brighton (and not exposed) but wouldnt expect a site visit to be necessary. The existing struct engineer didn’t consider it necessary to visit the property !.

Likewise, any structural engineers reading this feel free to PM me your details.

 

[cdbe]

I think mine is fairly similar - 2.5m of existing wall plus 5.5m of extension so 8m. Lateral stability was queried by the BC checking engineer. The SE provided a drawing with all the buttressing walls and a report, saying that he could prove it was ok (via extensive and complex calculations) but basically asked, based on his professional knowledge and experience, if they would just take his word for it - which they did!

Unfortunately I don't believe the SE is around any more. But at least you know what you want may be possible, although I think I may have a few more "red bits" than you.

Could be easier to just put the post in.

 

[Doitproper]

Many thanks for taking the time to post. Your case is not much different and I’m sure my situation will also work, just a case of finding the right guy to sign it off. Your case may be slightly different though - possibly the shear resistance of the building as opposed to the stability of the wall based on the comments on the drawing. Your SE argued the case, presumably because it was his design in the first place, next time he will probably err on the side of caution and want to install a post. Not because your wall is unstable and wont be there in 100 years but because the system makes it easier to install a post. One of the issues I’m finding is SE’s saying who will be liable if something goes wrong. It doesn’t really matter because the client usually ends up paying in any case.

Putting in a post may be the easier and cheapest solution but would that cause a cold line down the wall ?

Not sure whether the original file is visible so have reposted as a jpeg.

Once again, thanks for your views.

 

[^woody^]

If the dashed walls are to be removed, what's supporting at C?

Generally that kind of arrangement is pretty standard for an extension and knock-through, and should not require a wind frame at A-C, and building control would not tend to question it.

 

[Doitproper]

There is a beam between G&D which picks up beam AC. Also one between B&H. They will be within the floor to allow a flush ceiling within the opened up areas and into the extension.
My original thoughts were for a beam to span from H to the bifolds, and the beam between G&D. Seemed a simple arrangement avoiding bolted connections and would continue the structural form of the house into the extension. The cross beam AC (supporting the new dormer wall above ) could have been installed on beam GD with a spacer and avoid any reaction with the beam spanning to the bifolds. Never did do the calcs to find out which scheme was more economic.