Architect and structural engineer cost for a side extension (London)

[Sideextension]

Hello.

Can someone give me a rough estimate for the cost of an architect for a side extension (bedroom and small shower room) to a semi detached house in London, which will include opening up my living room and kitchen? This would need planning permission and potentially moving a staircase to create more space. I am not sure if the quote should include changes that may need to be made once the builders are in. One architect has said quoted me for every hour of work needed post planning permission. Are changes quite common once build commences?

It would be helpful to know what would a structural engineer cost on top of that.

Thank you.

@SideextensionThere should always be a contingency budget because something always goes wrong or wasn’t known about. It’s inevitable. People underestimate cost of flooring and hardware and costs creep up. Everything costs more than you think and you will need to make good the garden.

We haven’t used an architect recently so cannot say about costs. They will also know how much the engineer will charge too.

We’re in the SE but not London. 5 years ago we employed an architect to design our loft conversion and downstairs extension (only went ahead with loft conversion in the end).

Once we had plans in place, no further engagement with the architect was needed. Unless you’re doing something very unusual, experienced builders will typically crack on fine.

The planning team did raise a few concerns with our initial design and the architect worked on solutions for free.

Thanks, @FasterMichelin may I ask what the architect cost you at that time, and I can apply an inflation factor to it.
I have a quote of around 4k. But I am not sure how many changes that includes (pre build, not once build commences). To be fair I have already given the architects links to plans for other houses on the street since they are close to what I need.

I’ve looked over emails, it was £3150 inc vat.

I paid £5500 for design, planning permission and building drawings but it was for a ground floor side extension and loft conversion. I think from memory the single project was approx half of that. I'm in South London in a mid-terrace. That included structural engineering cost. Hope this helps x

@HROSESATTERS that sounds very reasonable! Would be great if you might message me the name and contact number (or website) of your architect, please. All my quotes are upward of 4.5k as of now.

We've just paid 3,600 ISH for drawings, planning submission and structural engineer calculations and drawings through Home Tales. We weren't doing anything super-designy though. Proper architect was more like 10k.

Hometales quoted me 5.5k and are currently turning out to be more expensive than 2 other architects.

A structural engineer's costs will be in addition to the architect's as you will require calculations for the staircase move, knocking the wall down and making sure your extension is not going to fall down. They will require the drawings before they will give a quotation but should be cheaper than the architect's price. I'm an office manager for them but no where near you unfortunately.

Possibly a smaller job- ours is just one floor. We found a 'proper' architect was at least 10k with calcs on top with no changes. Maybe the differential reduces for a bigger job or we just found weirdly expensive architects.