Structural engineer before or after planning permission?

[Sideextension]

Im embarking on a side extension. I belive the "usual" way is for a structural engineer to be consulted after planning permission has been granted. Now, this makes zero sense to me. Why would I not engage a structural engineer pre planning to liaise with architect to confirm whether the design submitted for planning was structurally feasible, and what it would cost me e.g. large beam or other remediation needed and i could then understand if some options be too expensive for my budget.

But the 2 architects I spoke with seem to say this it not how they work. What am I missing? This seems to be a no brainer to me, to first align the plans with an engineer before applying for planning permission. Wdyt?

Structural Engineer before planning - it costs to make changes to a planning permission after it’s granted ( and an architect would benefit from additional fees each time an amendment is submitted, I suspect!)

You are correct. An architect or planning agent will charge for amended plans so it’s in their interest for you to need to change it. Make sure your proposal is “buildable” before you apply for planning. It’s not the way a lot of people do it but it makes the most sense.

Do it before. Many structural engineers also do designs anyway, like my husband. You'd be gobsmacked by the number of plans he gets from very expensive architects that contain physical impossibilities. I am constantly amazed how many architects seem to get away with producing what is little more than a fancy picture for huge sums of money.

Architect here and unless you are doing something wildly outlandish then don’t waste money on a structural engineer before planning

They literally just need to do the calcs for building regs and planning drawings do not need to be changed.

Your architects are advising you correctly