Before anyone commits time or money to a full double storey extension design, the question that actually matters is a simple one: is this project viable at all? You don’t need a fully engineered set of drawings to answer that — you need an initial assessment, and it’s a lot more accessible than people expect.
What the initial assessment actually involves
Rather than starting with full accurate plans of the property — which most people don’t have to hand — the process works from what’s already available: photos of the property and any estate agent floor plans, if they exist. From that, we put together a basic concept sketch showing the proposed extension, with wall heights and general construction estimated from what’s visible.
That concept sketch then goes to a structural engineer for an initial review — not a fully engineered solution, just enough to answer whether the existing structure could realistically carry an additional storey, or whether it clearly can’t.
What it costs and how long it takes
Both parts — the basic concept plans and the structural engineer’s initial review — typically cost a few hundred pounds each, so the whole assessment usually comes to around £400 in total. That’s a genuinely small outlay next to the cost of a full double storey extension, and it gives a real answer before anyone commits further.
Why we sometimes waive the fee
Most of the time, we don’t actually charge for this. The goal isn’t the £400 — it’s finding out whether the project is viable so a client can get moving with it if it is. Having a cost attached means we’re not swamped with speculative enquiries from people with no real intention of proceeding, but if a project looks genuinely viable, we’re often happy to waive that fee. If it doesn’t look viable, having a fee in place means that work still gets paid for properly. Either way, being upfront about the cost — and flexible about when it applies — means clients know exactly where they stand from the start.
Building on Existing Extensions — The Structural Assessment You Need & Double Storey Extension Rules: Why Yours Might Be Different
