Where can I DIY and where can I DIYnot and need a Structural Engineer?

[WoOt]

Starting grounds works on an extension in a week, which I'm planning to build under permitted development and using a building notice.

The extension will be 4m deep by 10m long, and will have a flat roof with 1 or 2 skylights.

I've done the plans myself and it all seems fairly standard and straightforward. Just trying to figure out where I'll need to get an SE involved (if at all):

• Letter A: Opening up the old external wall to create a 5.5m opening. Assumption is that I'll need an SE for this.
• Letter B: Removing existing window to create an opening (exactly as wide as existing window). Assumption is that I don't need an SE as a lintel is already in place above the window.
• Letter C: This will house a standard set of French doors. Assumption is I won't need an SE and I can use an off the shelf lintel that is 300mm wider than the opening.
• Letter D: 5.5m opening for sliding doors. Assumption is I'll need an SE to calculate and specify a steel beam.
• Bonus question: will an extension like this require wind posts, and do I need an SE to specify these? Conscious that the wall between C and D might be vulnerable.

 

[Captain Nemesis]

using a building notice.

Good Luck

 

[sxturbo]

A & d will need se.

 

[tony1851]

As sx, A & D.

With regard to windposts, most SEs would specify one at A, or possibly at D, depending on how long the remaining wall returns are.
But in practice in most cases you would not need one if the other walls on the ground floor running left-to-right are brick or block.