When planning a home extension with sliding doors, understanding Building Regulations isn’t just about ticking bureaucratic boxes—it’s about ensuring your investment is secure, energy-efficient, and legally compliant. With extensive glazing becoming a hallmark of contemporary extension design, particularly with slimline sliding doors that maximise natural light and views, navigating the regulatory landscape has never been more important.
Building Regulations in England and Wales set minimum standards for the design, construction, and alteration of buildings. When adding sliding doors to your extension, three key areas of Building Regulations come into play:
Part Q (Security) – Addresses unauthorized access and mandates security standards for doors and windows Part K (Protection from Falling, Collision and Impact) – Covers safety glass requirements Part L (Conservation of Fuel and Power) – Ensures adequate thermal performance
These regulations work together to create a comprehensive framework. While you might focus on aesthetics when selecting glass box extensions with expansive glazing, Building Control will scrutinise whether your doors meet security standards, incorporate safety glass, and achieve the required U-values for thermal efficiency.
PAS 24 (Publicly Available Specification 24) is the British Standard developed by BSI in collaboration with the Metropolitan Police and security experts. It’s a rigorous test specification designed to assess the security performance of doors and windows against forced entry attempts.
Unlike European security ratings which use RC (Resistance Class) levels, PAS 24 is specifically tailored for the UK market and is a binary pass/fail certification. Products either meet the standard or they don’t—there’s no middle ground.
The certification involves subjecting doors to a 15-minute continuous attack using various methods that mimic real-world burglary attempts:
The test examines the entire system as a unit—frame, glazing, locks, and installation—not just individual components. This holistic approach ensures that weak points can’t be exploited during an attempted break-in.
Approved Document Q, which came into force in 2015, mandates that all new dwellings must have doors and windows that are “sufficiently robust to resist physical attack by a casual or opportunistic burglar.”
Part Q applies to:
For extensions, this means any new doors or windows you’re adding must comply with current standards, regardless of when your original property was built. If you’re creating a floating corner design with multiple sliding door panels, each accessible opening must meet Part Q requirements.
The most straightforward way to demonstrate Part Q compliance is by specifying doors certified to PAS 24:2016 or later. Alternative standards exist (such as STS 201, LPS 1175, or STS 202), but PAS 24 remains the most widely recognized and readily available certification in the UK market.
At Minima Sliding, all Ultraline sliding doors meet PAS 24:2016 certification as standard, providing peace of mind that your extension will satisfy Building Control requirements without costly upgrades or last-minute changes.
The PAS 24 standard has evolved significantly since its introduction:
PAS 24:2012 – Original standard PAS 24:2016 – First major revision with enhanced testing protocols PAS 24:2022 – Significant update with tougher attack methods PAS 24:2022+A1:2024 – Latest amendment (September 2024) introducing thermal attacks and twisting resistance
The 2024 amendment specifically addresses new burglary techniques, including thermal attacks on cylinder locks and twisting methods that criminals have developed to bypass older security features. Products certified to the latest standard now require 3-star TS007-1 cylinders with enhanced resistance to drilling, picking, bumping, snapping, and thermal weakening.
When specifying doors for your extension, it’s worth confirming that your supplier’s certification meets the current standard. While older certifications remain technically valid, building to the latest specification provides better long-term security and future-proofs your investment.
Beyond security, safety glass requirements under Part K must be carefully considered. This is particularly crucial for large format sliding doors where extensive glazing creates potential collision hazards.
Safety glass is mandatory for:
Safety glass must comply with BS EN 12600 (impact classification), typically using either toughened glass (BS EN 12150) or laminated glass (BS EN 14449). For sliding doors, toughened glass is standard in moving panes, while laminated glass may be specified for fixed panes or where additional security is required for Part Q compliance on ground floor installations.
Energy efficiency requirements under Part L add another layer of complexity. Your sliding doors must achieve a maximum U-value of 1.2 W/m²K to comply with current Building Regulations.
For extensions, there’s also the “25% glazing rule” to consider—the total glazed area (windows plus doors) should not exceed 25% of the floor area unless you conduct a whole-dwelling SAP (Standard Assessment Procedure) calculation to demonstrate overall energy compliance.
This can present challenges for glass box extensions or designs with floating corners where maximizing glazing is the architectural intent. However, several strategies can help:
Advanced glazing technology: Minima Sliding’s standard double-glazed doors achieve a U-value of 1.2, meeting regulations precisely. For projects requiring enhanced thermal performance or to offset additional glazing elsewhere, triple-glazed options achieve an impressive U-value of 0.7—well below regulatory minimums and future-proofing your extension against anticipated stricter standards.
Whole-dwelling calculations: Working with your architect or energy assessor to model the entire property’s thermal performance can demonstrate compliance even when glazing exceeds 25%. This approach accounts for improvements elsewhere in the building envelope.
Thermal breaks and warm-edge technology: Quality aluminium frames with thermal breaks, low-e coatings, and warm-edge spacer bars significantly improve overall performance. These features are standard in professional sliding door systems but may be absent in budget alternatives.
Achieving PAS 24 certification for sliding doors is considerably more difficult than for hinged doors or windows. The large moving panels, minimal frame sight lines, and flush thresholds that make sliding doors architecturally desirable also create potential security vulnerabilities.
Common weaknesses in sliding door systems include:
This explains why relatively few sliding door systems on the UK market hold genuine PAS 24 certification when tested as doors (rather than windows, which have less stringent requirements). Systems that do achieve certification, such as Minima Sliding’s Ultraline doors, incorporate sophisticated engineering solutions including electric locking systems with concealed stainless steel bolts, reinforced frame profiles, and enhanced glass bonding techniques.
The electric locking system deserves particular mention—activated via a wall switch or smart home integration, it engages a stainless steel bolt concealed in the top frame, providing superior security to traditional manual multipoint locks while maintaining the minimal aesthetic that defines premium sliding doors.
Even the most compliant door will fail Building Control inspection if poorly installed. Installation is where many projects encounter problems, leading to delays, remedial work, and additional costs.
Critical installation considerations:
Professional installers understand these requirements intimately. Minima Sliding’s in-house installation teams work exclusively with Ultraline systems, developing expertise in Building Control requirements across different local authorities. They survey projects carefully, ensuring structural openings accommodate proper fixings and drainage, and coordinate inspections at appropriate stages.
Documentation requirements:
Building Control typically inspects at three stages: plan review before work begins, fixed frame inspection before glazing installation, and final completion inspection. Having all documentation ready and working with installers familiar with the process significantly smooths this journey.
Do I need PAS 24 if I’m replacing doors in an older extension? It depends. Like-for-like replacements may fall under exemptions, but enlarging openings or significantly altering frames typically triggers full compliance with current standards. Always check with Building Control before purchasing—what was compliant when your extension was originally built may not satisfy today’s requirements.
What if my sliding doors are on the first floor? Part Q applies to “easily accessible” windows and doors. Ground floor and basement levels always require compliance. First-floor openings need assessment—if accessible from balconies, fire escapes, flat roofs, or adjacent structures, they’re treated as ground-level risk and require PAS 24 certification.
Can I use non-certified doors if they’re higher specification? No. Building Control requires independent third-party certification from UKAS-accredited laboratories. Marketing claims about “exceeding PAS 24” or “equivalent security” without certification won’t satisfy Building Control. The certification proves the entire system—not just components—passed rigorous testing.
How do I verify my doors are genuinely PAS 24 certified? Request the certificate number, test date, and exact system configuration tested. Genuine certifications specify frame dimensions, glazing types, hardware specifications, and installation requirements. Be wary of vague claims or “tested to PAS 24 principles”—legitimate suppliers provide complete documentation readily.
Building Regulations continue evolving, typically becoming more stringent rather than relaxed. Recent amendments to PAS 24 and anticipated changes to Part L energy requirements suggest this trajectory will continue.
Specifying doors that exceed minimum requirements provides future-proofing benefits:
Successfully navigating Building Regulations for sliding doors in extensions requires balancing security (Part Q and PAS 24), safety (Part K glazing standards), and energy efficiency (Part L thermal performance). These requirements aren’t obstacles—they’re frameworks ensuring your extension is secure, safe, and thermally efficient.
The key is early engagement with Building Control and specifying certified systems from manufacturers with proven track records. Professional installation by experienced teams familiar with regulatory requirements eliminates the most common causes of delays and rejections.
For homeowners and architects specifying slimline sliding doors, selecting systems that offer PAS 24 security certification as standard, compliant U-values in line with current Building Regulations, and specialist installation services provides a clear route to a compliant and successful extension project.
Your extension is a significant investment in your home and lifestyle. Ensuring it meets all Building Regulations protects that investment while delivering the security, safety, and performance you deserve. For more information about compliant sliding door systems or to discuss your specific extension project, visit Minima Sliding’s showrooms to see award-winning Ultraline doors in person and speak with experts who can guide you through the compliance journey.