Building Control questions can feel stressful, but most inspections follow a predictable pattern. In this guide, we explain what inspectors look for, the questions they typically ask, and how you can prepare so your project stays compliant and avoids delays.
Not sure how to handle Building Control questions?
We guide homeowners through Building Control from first drawings to final sign-off.
Understanding Building Control Questions
When you begin a home extension, loft conversion, garage conversion or garden room, Building Control becomes a key part of the journey. Inspectors ask questions to confirm that your work meets the Building Regulations — covering structure, insulation, fire safety, drainage and more.
Although some questions can feel technical, most are simply checking that your builder is following approved details and that no corners have been cut. As long as the work is properly planned and built, the process should be collaborative rather than confrontational.
For deeper background on the regulations themselves, you may find our main guide helpful: Building Regulations – Complete Homeowner’s Guide.
Common Building Control Questions During Site Inspections
There is a pattern to the questions Building Control typically asks at each stage. Below is what you can expect.
1. Foundations / Groundworks Questions
- “What depth are the foundations and how was the ground bearing checked?”
- “Can I see the reinforcement layout?”
- “How far are the footings from nearby drains or trees?”
2. Drainage Inspections
- “Are the new pipes correctly bedded and at the right fall?”
- “Can we test the drains before they’re covered?”
- “Where does the rainwater discharge?”
3. Structural and Steelwork Questions
- “Where are the bearings and padstones for the RSJ?”
- “Do you have structural calculations for this beam?”
- “Is this in line with the engineer’s approved drawings?”
Structural calcs are usually required. If you need a refresher: Structural Calculations – When Do You Need Them?.
4. Fire Safety (Part B) Questions
- “What escape route is being maintained?”
- “Where are the mains-wired interlinked smoke alarms?”
- “Are the doors providing the correct fire resistance?”
5. Insulation / Energy Efficiency (Part L) Questions
- “What are the U-values for your walls, roof and floor?”
- “Have thermal breaks been installed correctly?”
- “Is the building fabric meeting the updated Part L requirements?”
More detail is available in our dedicated guide on U-values: Building Regulations U Values Explained.
6. Final Inspection Questions
- “Can I see the ventilation flow rates?”
- “Where is your electrical certificate (Part P)?”
- “Do you have the boiler commissioning sheet?”
- “Have all drainage tests been completed?”
Many homeowners find the final sign-off guide useful here: Building Regulations Completion Certificate – What It Is and Why You Need One.
How to Prepare for a Building Control Visit
Here is a simple step-by-step checklist to help you prepare confidently.
| Step | What to Do |
|---|---|
| 1. Review approved drawings | Have printed or digital copies ready so the inspector can cross-check details. |
| 2. Confirm structural details | Have structural calculations available, especially before steelwork installation. |
| 3. Keep any hidden work uncovered | Don’t backfill or plaster until Building Control has seen drainage, insulation or steelwork. |
| 4. Ask questions early | If you're unsure, call Building Control before the visit — they’re usually very helpful. |
| 5. Ensure safety on site | Clear pathways, stable ladders, and no live, exposed electrics. |
Unsure what Building Control will ask?
We’ll review your drawings and highlight any areas inspectors usually query.
Quick Costs Snapshot: Typical Building Control Fees
Fees vary by council or private inspector, but these typical ranges help you plan ahead.
- Single-storey extension: £450–£750
- Double-storey extension: £650–£950
- Garage conversion: £450–£700
- Loft conversion: £500–£850
- Garden room (under 30m²): £300–£550
For more detail on approval routes, see: Building Regulations Approval Explained.
Common Gotchas That Trigger Building Control Questions
1. Buried Drainage Without Prior Testing
All drainage must be inspected before backfilling. Failing to do this can mean digging everything back up.
2. Hidden Steelwork
RSJs and padstones must remain visible until the inspector has checked installation, bearings and fire protection.
3. Missing Insulation Photos
If insulation is installed before the visit, take detailed photos showing depth, type and continuity.
4. Unsupported Alterations in Outbuildings
If you're modifying outbuildings, check the specific regulations: Outbuildings Building Regulations Explained.
5. Electrical Works Without a Part P Certificate
Electrical work must be completed by a competent person. Learn more: Building Regulations Part P – UK Rules.
FAQs: Building Control Questions
Below are the most common homeowner questions, based on your Building Control query list.
Is Building Control a legal requirement?
Yes. Any structural work, conversion, extension, drainage alteration or electrical/mechanical installation that falls under the Building Regulations must be inspected and approved. Planning permission and Building Control are two separate systems.
Can Building Control stop work?
They can request unsafe or non-compliant work to be rectified. In extreme cases they may issue a notice, but most issues are resolved through discussion.
What stages do Building Control visit?
Typical stages include foundations, drainage, oversite, structural steelwork, insulation, first fix, and final completion. Your inspector will confirm the exact schedule.
How often do Building Control visit?
It depends on the project type. Extensions and lofts normally require 4–7 visits; garage conversions may need fewer.
Can Building Control change their mind?
Yes — especially if site conditions differ from the drawings. This isn’t unusual; it’s simply part of ensuring compliance.
Can I ask Building Control questions?
Absolutely. They prefer early clarification rather than discovering issues after work is covered up.
What powers do Building Control have?
They can require non-compliant work to be opened up, re-done or tested. They cannot enforce planning rules.
Can Building Control fine you?
While they typically do not issue fines directly, councils can take enforcement action for serious breaches. Most situations are resolved informally.
Next Steps & Useful Guides
- Building Regulations – Complete Homeowner’s Guide
- Plans for Building Regulations
- Retrospective Building Regulations Time Limit
- Building Regulations for Garden Rooms
- Building Regulations Approval
Key Facts Snapshot
- Legal Requirement? Yes — for most structural work, conversions and drainage changes.
- Typical Visits 4–7 depending on the project size.
- Most Common Questions Foundations, drainage, insulation, fire safety, structure.
- Key Documents Structural calcs, Part P cert, boiler commissioning, ventilation tests.
- Final Sign-Off Needed? Yes — completion certificate proves legal compliance.
Need help handling Building Control?
We produce compliant plans, provide guidance and help you secure final approval smoothly.
Helpful resources:
Planning Portal – National Guidance
GOV.UK – Planning Permission Guidance
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