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North England & Scotland - 0161 820 3230
Structural Engineering for Extensions
Beam sizing over openings, foundation design, roof junctions and contractor drawings — full structural calculations for your extension. One dedicated engineer, and a delivery date you choose.
Three things you always know
Every job runs through the same process, so every customer gets the same three answers.
The price, before you commit
Tell us about the project and we’ll tell you the price and the steps that follow. No hourly rate. If the job changes, there is a free change request on every job.
The turnaround, chosen by you
Pick how fast you need it, and pay less if you can wait. You get a date to work back from.
Every step, in one place
Never wonder where it’s up to — just look. Your project hub shows what is happening now, what is next and anything we need from you, with your drawings, documents and invoice alongside. Share it directly with everyone involved in your project.
House Extension Structural Engineer Drawings & Calculations
Your project’s dedicated coordinator will work closely with architects and any other design professionals employed on the extension. They will aim to work together to help create a design that is aesthetically pleasing while ultimately being structurally sound.
When brought onto a project, a PorthouseDean structural engineer will bring expertise as well as a unique perspective on a number of factors. Key benefits include:
- Impact Assessment: An engineer will consider what impact, if any, an extension may have — will it cause any cracking to walls due to beam deflection, improper construction techniques, inadequate foundation sizing and settlement, etc.
- Implications of Design: Your project coordinator will pay particular attention to considering how an extension’s size and shape could affect design calculations, as well as if it will cause complications and additional costs.
- Quality Work: An independently audited ISO 9001:2015 quality management system ensures that any work we do is of the highest possible standard.
- A delivery date you choose: You get a clear price before you commit, and you pick the delivery date that suits your build. Need it sooner? Pick an earlier date and the price follows it.
Our Architectural Partners
What we cover
Everything Building Control needs to approve your project first time.
- Steel beam sizing over every new wall opening
- Foundation design — strip, pad and engineered options
- Assessment of existing structure where new loads from extension apply
- Roof junction calculations, wall plate and rafter connection details
- Drainage impact review and foundation clearance distances
- Wind bracing for infill panels and party wall structural details
- Extension size and shape implications on overall structural design
- Contractor drawing pack — unambiguous instructions for site
What every quote includes
We don't strip things out to make the headline price look cheaper. This is the full package, every time.
Full structural calculations
Beam specs, column calculations, foundation details, load assessments — everything your project needs.
Building Control documents
Submission-ready, and 100% approved by building control: if yours aren't, you get a refund. Your engineer handles any queries from BC directly.
Contractor pack
Clear drawings and instructions to build from on site. Dimensions, connections and installation notes included.
A free change request
Building Control changes, contractor modifications, design adjustments — the first change is on us, and further changes cost less than a new quote.
£500,000 PI insurance
Professional indemnity cover on everything we produce.
Ground conditions check
Site-specific ground assessment integrated into the foundation design. Helps avoid unexpected foundation costs.
Virtual site visit
Included with every project. Your engineer guides you through capturing measurements and photos via video call.
Dedicated engineer
One person who knows your project. Not a different voice every time — same engineer from quote to Building Control.
Pay by card, bank transfer, or Klarna — split into 3 interest-free payments. See the full process →
How it works
From quote to delivery, the same process every time. No surprises.
Tell us about your extension, or upload the drawings you already have. Your price is emailed, not called back. Every quote is reviewed by an engineer. No commitment until you're ready, and the quote stays live.
One dedicated structural engineer is assigned. They review your drawings, establish what's needed on site, and complete a virtual site visit (included). Single point of contact from instruction through to Building Control sign-off.
Full extension calculations on the date you choose — beam specs over every opening, foundation design, roof junction and wall plate details. Contractor pack included. Your engineer handles any Building Control queries that come back.
A delivery date you choose. 100% building control approval, or a refund. Dedicated engineer throughout. See how it works →
Ready to get your extension calculations?
A clear price and a delivery date you choose. One dedicated engineer from instruction to Building Control. Quote stays live — no pressure.