The Process
From enquiry to compliance report
Getting a Part L Section 10.10 assessment is straightforward. Here is exactly what happens at each stage — from your first contact with us through to building control sign-off.
Step 01
Submit your enquiry
Get in touch via our contact form or by email. Tell us about your project — the type of extension, approximate size, and building regulations specification if available. We will confirm whether a Section 10.10 assessment is required and provide guidance on fees.
You do not need to have finalised your drawings at this stage. A brief description of the project is enough for us to confirm scope and provide a quote.
Step 02
Send us your plans and specifications
Once you are happy to proceed, send us your extension drawings, floor plans, and construction specifications. We accept drawings in any standard format — PDF, DWG, or scanned copies.
We will also need details of the existing dwelling (age, construction type, heating system) and any lost openings created by the extension. If a site visit is required we will agree a fee for this with you.
Step 03
We carry out the SAP assessment
Our assessors carry out the full Section 10.10 energy assessment using the Standard Assessment Procedure (SAP 10.2). We model the existing dwelling and the proposed extension together, calculating the dwelling primary energy rate (DPER), dwelling emission rate (DER), and fabric energy efficiency rate (DFEE).
These calculated rates are compared against those of the dwelling with a notional extension — a reference extension built to minimum Part L standards. Compliance is demonstrated where the actual rates do not exceed the notional rates.
Step 04
Receive your compliance report
We deliver a professionally formatted compliance report setting out the assessment methodology, inputs, outputs, and compliance conclusion. The report is clear, well-structured, and formatted for direct submission to your building control body.
Turnaround is typically within a few working days of receiving all required information. We will confirm the expected delivery date when we receive your documents.
Step 05
Submit to building control
Submit the report to your local authority building control (LABC) or approved inspector alongside your other completion documentation. The report demonstrates compliance with Part L Section 10.10 and gives building control what they need to sign off your extension.
If building control raises any technical queries about the report, we are available to respond directly. Our fee includes follow-up support at this stage.
Step 06
Ongoing support if needed
If your specification changes during the build — for example, if you switch to a different glazing unit — we can update the assessment to reflect the revised specification. We will agree any additional fee with you before proceeding.
We are also available to advise during the design stage if you want to understand how different glazing specifications or extension configurations will affect compliance before finalising your plans.
Common Questions
Frequently asked questions
How do I know if my extension needs a Section 10.10 assessment?
If the total area of windows, roof windows, rooflights, and glazed doors in your extension exceeds 25% of the extension's floor area (plus any lost openings), a Section 10.10 assessment is required. If you are unsure, send us your plans and we will confirm.
How long does the assessment take?
Once we have received all the information we need, we typically deliver the compliance report within a few working days. We will confirm the expected turnaround when we receive your documents.
What if my glazing specification changes during the build?
If the glazing specification changes — for example, if you switch to a different unit or frame — we can update the assessment. We will agree any additional fee with you before proceeding.
Will building control accept your report?
Yes. Our reports are formatted to meet the expectations of both local authority building control (LABC) and approved inspectors across England and Wales. If building control raises any queries, we respond directly.
Do I need to have finalised my drawings before contacting you?
No. You can contact us at any stage of the design process. We can advise on how different glazing specifications or configurations will affect compliance before you finalise your plans.
Do you cover the whole of England and Wales?
Yes. We provide assessments for projects across England and Wales, regardless of local authority area.
Ready to get started?
Send us your plans and we will provide a fast, accurate Part L Section 10.10 compliance report — no jargon, no delays.