Do I need a structural engineer?

[Kate80]

I’ve got an architect drawing up some plans for a rear single storey extension and an extension to existing dormers. I’m a novice at house renovations and don’t know if I also need a structural engineer?

I’ve tried to do some research on the internet but am getting conflicting information. Some people think the architects drawings will be good enough for the builder to work from but I may need a SE to do the calcs before a builder can quote for the work. Some people say that a SE is needed to do more detailed drawings for the builder to work from. Some people say I need SE calcs for building regulations.

Any advice on this would be greatly appreciated.

 

[Nakajo]

If the architect cannot answer these questions, then I would have grave concerns about their competency.

 

[Ian H]

On ours the architectural technician (bell end) drew the plans and the more detailed building regs drawings, then the SE (great guy) calculated the steel and timber sizes that were on the drawings.

 

[^woody^]

Who ever is drawing the plans should either do it or arrange someone more competent to do the structural design.

Either way they should be telling you.

If they have not explained things already, then I would be concerned.

 

[Notch7]

If there are parts of the build that require structural elements, usually steel beams, then you need a structural engineer to calculate. Extending a dormer sounds like something thst might need calcs.

A builder normally quotes from building regulation drawings -which may have structural engineers details incorporated.

 

[Leofric]

Have you asked your architect ?
The builder should be able to build from the architect's drawings if you are paying them to obtain building regulations approval
(that is what they are for !).
A structural engineer is used to prepare structural calculations as required for structural work which the architect will identify during preparation of bldg. regs drawings. The architect would normally arrange for the SE to do the calcs and invoice you as the client.
The architect should explain all this to you if you ask. If they can't they are not an architect ( or architectural technician )

 

[tony1851]

Sometimes it's a chicken-and-egg situation.

Most drawings showing steel beams will just stipulate "steel beams to SE's specification" or suchlike.

So far as the builder is concerned, the 'steel beam' could be anything from a piece of angle iron to a 300-deep fabricated job, so they can only guestimate the price.

Slightly off topic but I once knew a builder who used a scrap piece of railway track as a beam; the inspector was bemused.

 

[Nakajo]

The noise of the freight trains at night must have been unsettling

 

[Leofric]

So SE calcs are required so the builder can quote on the correct size steelwork if it is required ; and preferably go out for quotations after planning and bldg regs approval has been obtained.

 

[Nakajo]

I know someone who applied for permission to erect an old railway signal box in their garden. One of the objections was a concern about the noise of the points switching at night.