What types of sliding door are available?

The main types are inline sliding (panels slide behind each other on tracks), lift and slide (panels lift off seals before sliding for better weather performance), and pocket sliding (panels slide into a wall cavity). Inline is most common and affordable. Lift and slide offers the best weather sealing.

What U-value do sliding doors need?

Under Part L of UK Building Regulations, replacement doors must achieve 1.4 W/m²K or better. New build notional spec is 1.2 W/m²K. Quality aluminium sliding doors with argon-filled double glazing and low-E coating typically achieve 1.3-1.5 W/m²K.

How wide can sliding doors be?

Individual panels are typically 800-2000mm wide. Inline sliding doors commonly span 2-4m total. Lift and slide systems can span up to 6m or more with larger panels. The structural opening and lintel must support the weight across the full span.

Are sliding doors more secure than bi-fold doors?

Modern sliding doors with multi-point locking systems are very secure. Lift and slide doors are particularly secure as the panel drops onto the track when locked. Both sliding and bi-fold doors can achieve PAS 24 security ratings. Laminated glass further improves security.

Do sliding doors need a threshold?

Yes. Standard thresholds are 20-30mm high. Low thresholds (15mm or flush) are available for Part M accessibility compliance. Flush thresholds require careful drainage detailing to prevent water ingress. A low threshold adds £200-400 to the cost.

TradeCalculator.co.uk

Sliding Door Calculator

Calculate sliding patio door costs, sizes and U-values for inline, lift & slide and pocket sliding doors with UK Part L compliance checking.

Door TypeInline most common for domestic

Frame MaterialAluminium gives slimmest sightlines

GlazingTriple for better thermal performance

Opening Width

Structural opening width

Opening Height

Standard 2100mm

How We Calculate This

This calculator estimates sliding door costs based on opening dimensions, door type, frame material and glazing spec.

The formula

Total = (Area × Base Rate × Frame Factor × Glazing Multiplier) + Installation

Base rates vary by door mechanism (inline, lift & slide, pocket)
Frame factor adjusts for material
Triple glazing adds ~30% to glass cost
Weight estimated at ~38 kg/m² for double glazed aluminium

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.