Tendering and estimating, 29 October 2026
Checking a spec against building regs before you price
Before you price, read the spec against the Approved Document for each element you're doing, check who will sign the work off (building control or a competent person scheme), and confirm every product named is suitable for where it's going. Raise anything that doesn't fit as a query or a qualification. Don't price round it and hope.
Why check the spec before you price?
Because if the work doesn't comply, the person doing it can be prosecuted and fined, and building control can make you pay to put it right. GOV.UK is plain about it: non-compliant work can mean prosecution, a bill to fix faulty work, and missing certificates when the owner comes to sell. If you priced the spec as drawn, the cost of the fix usually lands on you.
A spec is written by someone who may never have fitted the product. It can name an adhesive that isn't approved for the board, a coverage that doesn't match the pack, or a detail that predates the current Approved Document. Your job before pricing is to find those, not to design the building.
Who signs the work off?
It depends on the work. Building regulations approval comes from your local authority building control, a private registered building control approver, or for higher-risk buildings (at least 7 storeys or 18 metres plus certain uses) the Building Safety Regulator. Some work can be self-certified through a competent person scheme instead, and some is exempt.
Higher-risk buildings go to the Building Safety Regulator, not local building control. Expect a longer process and check the main contractor's gateway programme.
The work must still meet safety and energy standards. Check exceptions: heating systems, fuse boxes, glazing units and circuits near baths and showers still need approval.
Your scheme notifies building control and the client gets a certificate within 8 weeks of completion. Price the scheme's notification fee.
Someone must apply to the local authority or a registered approver. Find out who, and whether it's full plans or a building notice.
The full plans route gets a decision within 5 weeks, or 2 months if agreed, and usually a completion certificate within 8 weeks of finishing. A building notice lets work start 2 days after submission but gives no formal plan approval, so the risk sits with whoever builds it.
Which Approved Documents do you check?
Only the ones that touch your package. A roofer checks fire spread, energy and falls; an electrician checks electrical safety and fire alarm interfaces; a heating engineer checks combustion, energy and ventilation. Use the edition that applies to the job. Approved Document B was updated on 16 September 2026 with guidance on second stairs and evacuation lifts in taller residential buildings, and 2026 editions of Approved Documents L and F have been published. Ask the designer which edition and transitional date the scheme was designed to.
What does a coverage error cost?
More than people expect, because it feeds the order, the labour and the waste. For example, say a flat roof spec names an adhesive that isn't suitable for the XPS insulation board, and gives a coverage of 0.75 m² per board when the board actually covers 1.44 m².
Board count on a 120 m² flat roof, wrong coverage vs right coverage
Illustrative roof area and coverage figures.
| Boards needed at 0.75 m² per board120 ÷ 0.75 | 160 |
| Boards needed at 1.44 m² per board120 ÷ 1.44 = 83.3, round up | 84 |
| Boards over-ordered160 − 84 | 76 |
| Board count overstated by76 ÷ 84 | 90% |
Overstate the materials and you lose the job on price. Understate them, or price an adhesive that fails, and you pay for the strip-out. Over-order and the surplus goes in the skip.
What do you do when the spec doesn't comply?
Put it in writing before you price, and price what you're confident complies. You aren't the designer, but you can be the one left holding a non-compliant detail.
- Raise a tender query.
Quote the drawing or clause, say what you think is wrong and why, and ask for confirmation. Keep it factual.
- If there's no answer by the deadline, qualify.
State the assumption you priced on, for example "Priced on adhesive approved by the board manufacturer for XPS; the specified adhesive is excluded."
- Price the alternative separately.
Show the compliant option as its own line so the client can see the difference.
- Keep the record.
If the detail changes after award, it's a variation, and your query is the evidence. See final accounts for subcontractors.
For wording, see tender qualifications and exclusions. For how to take quantities off the drawings in the first place, see quantity take-off and how to measure PDF drawings.
Can AI check a spec against building regs?
It can do the reading: pull every product and detail out of a 22-page tender pack, compare coverage and U-values against data sheets, and list the items that look wrong. It can't take legal responsibility for compliance, and it can be wrong. Treat its output as a list of questions for you, the designer or building control to answer. More on this in can AI check building regs and what to check before using AI for tender pricing.
If you're unsure whether something complies, ask building control or the scheme's technical helpline before you price. For structural or fire questions, get the designer or a fire engineer to confirm in writing.
Where Nexley fits
Nexley is the AI back office for UK trade firms: five AI assistants run your tenders, quotes, buying, scheduling and invoicing. It connects to the tools you already work in, you run it all from WhatsApp, and you approve everything. £799 a month.
Nexley reads the tender pack and drawings you forward on WhatsApp or email, lists every product and detail in your package, checks coverage and suitability against the maker's data where it can, and flags anything that looks out of line with the Approved Documents. You get the list of queries to send and decide what to price; nothing goes to the client without your approval.
Common questions
Is it the contractor's job to check the design complies?
The designer is responsible for the design, but the person carrying out the work must also make sure it complies, and can be prosecuted if it doesn't. Raising queries before you price protects you and the client.
Do Approved Documents apply in Scotland and Northern Ireland?
No. Scotland and Northern Ireland have their own building standards and guidance. Wales has its own versions of some Approved Documents. Check which system the site falls under before you price.
What if the client says to price it as drawn?
Price it as drawn, but put your concern and the assumption in your tender qualifications. If building control later rejects the detail, the fix is a variation, and your written query is your evidence.
How do I know which edition of an Approved Document applies?
Ask the designer or building control which edition the application was made under. Changes usually come with transitional arrangements tied to when the application was made and when work started.
Sources
- GOV.UK: Building regulations approval
- GOV.UK: How to apply for building regulations approval
- GOV.UK: When you don't need building regulations approval
- GOV.UK: Use a competent person scheme
- GOV.UK: Competent person schemes, types of building work
- GOV.UK: Fire safety, Approved Document B
- GOV.UK: Conservation of fuel and power, Approved Document L
- GOV.UK: Amendments to Approved Documents L and F, Circular 04/2026
Every rule, rate and date above was checked against these sources on the date shown at the top.
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