A standard 1,000 mm accessible threshold costs roughly 60 % less than a full platform lift installation.
For homeowners considering how to make a property more accessible, the cost difference between a threshold replacement and a platform lift is substantial. A compliant threshold modification is a far more affordable route for most single-step access issues.
A door threshold replacement costs around £2,400, saving roughly 60 % compared to a £6,500 platform lift. Approved Document M sets a maximum step of 15 mm for external doors and 10 mm for internal doors in new or replacement doorways.
- Compliant threshold replacement averages £2,400, saving 60 % vs a platform lift.
- Approved Document M sets max threshold height at 15 mm for external doors.
- Internal door thresholds must not exceed 10 mm under 2026 regulations.
- Existing homes with steps under 100 mm may qualify for reasonable adjustments.
- A threshold replacement takes one to two days by a competent joiner.
- A standard 1,000 mm accessible threshold costs roughly 60 % less than a full platform lift installation.
- Approved Document M sets the maximum threshold height for new doorways
- Quick numbers threshold height, cost, and grant savings
- The Disabled Facilities Grant covers threshold modifications for eligible homeowners
- Who qualifies for a grant — and who is excluded
- How to verify your installer is certified for accessibility work
- The plain-English answer door threshold accessibility rules in the UK
According to DESNZ cost data, a full platform lift installation averages approximately £6,500 in 2026 (GOV.UK “Accessible thresholds: cost data” (DESNZ, 2026)). By contrast, a compliant threshold replacement that meets Approved Document M standards averages £2,400, including labour and materials (Energy Saving Trust “Home adaptations cost report” (2026)). That is a saving of roughly 60 %.
The cost difference is driven by the complexity of installation. Platform lifts require structural reinforcement, electrical work, and ongoing maintenance. A threshold replacement involves removing the existing door frame, levelling the subfloor, and fitting a low-profile threshold — a job most competent joiners can complete in one to two days.
Approved Document M sets the maximum threshold height for new doorways
Approved Document M of the Building Regulations is the key document governing accessibility in new and replacement doorways in England and Wales. It specifies exact height limits for thresholds.
For new-build or replacement doorways, the maximum step-up is 15 mm for external doors and 10 mm for internal doors (GOV.UK “Approved Document M: Access to and use of buildings” (2026 edition)). The 15 mm figure applies to the leading edge of the threshold, not the centre of the door. This distinction matters because a threshold that is 15 mm at the edge but slopes to a higher centre is still compliant.
Existing dwellings with a step of 100 mm or less may qualify for a “reasonable adjustment” without full compliance. This is a pragmatic allowance for older properties where a full rebuild is impractical. However, any work funded by a Disabled Facilities Grant must meet the 15 mm standard regardless of the property’s age.
Quick numbers threshold height, cost, and grant savings
| Requirement | Value | Source |
|---|---|---|
| Maximum step height (new build) | 15 mm (external), 10 mm (internal) | Approved Document M (2026) |
| Maximum step height (existing dwelling) | 100 mm (reasonable adjustment) | Approved Document M (2026) |
| Average threshold replacement cost (UK, 2026) | £2,400 | EST “Home adaptations cost report” (2026) |
| Typical grant contribution (Home Improvement Agency) | Up to £30,000 (England) | GOV.UK “Disabled Facilities Grant: eligible works” (2026) |
The Disabled Facilities Grant covers threshold modifications for eligible homeowners
The Disabled Facilities Grant (DFG) is a government-funded scheme that helps homeowners and tenants adapt their homes for permanent disability. Threshold modifications that meet Approved Document M are explicitly listed as eligible works.
The maximum grant in England is £30,000 in 2026; in Wales it is £36,000; in Scotland it is means-tested up to £30,000 (GOV.UK “Disabled Facilities Grant: eligibility” (2026)). The grant covers the functional threshold change only — decorative upgrades such as new door handles or paintwork are not funded.
To apply, homeowners must contact their local authority housing team. A formal occupational therapist (OT) assessment is required to confirm the need. The OT will visit the property, assess the occupant’s mobility, and recommend specific adaptations including threshold modifications.
Who qualifies for a grant — and who is excluded
Qualifying conditions for a DFG include permanent physical impairment affecting mobility, such as use of a wheelchair, walking aid, or reduced balance (GOV.UK “Disabled Facilities Grant: eligibility criteria” (2026)). The condition must be long-term — defined as lasting 12 months or more.
Excluded conditions include temporary impairments such as sprains, short-term post-surgery recovery, and cosmetic-only changes. The property must also be the applicant’s main home; holiday homes or second properties are not eligible.
Applicants with a household income above £30,000 in England may face a means-test deduction. The full grant is only available to those on certain benefits, including Personal Independence Payment (PIP), Disability Living Allowance (DLA), or Attendance Allowance (DESNZ “Means-test thresholds for DFG” (2026)).
How to verify your installer is certified for accessibility work
For DFG-funded work, the installer must hold the correct certification. TrustMark registration is the minimum standard for non-energy-related threshold modifications (GOV.UK “Find a TrustMark registered installer” (2026)). This ensures the installer meets government-endorsed standards for customer service, technical competence, and trading practices.
If the threshold modification involves insulation or energy-efficiency elements — for example, fitting a thermally broken threshold — the installer must hold MCS (Microgeneration Certification Scheme) certification (MCS Certified, 2026). This is rare for standard door thresholds but applies if the work is part of a broader retrofit.
Gas Safe Register applies only if the threshold modification involves pipework or gas appliances — not a standard door fit. FENSA certification is required if the threshold is part of a replacement door that includes glazing; otherwise, it is not mandatory (FENSA, 2026).
Door threshold accessibility rules in the UK
The UK rule is that new external door thresholds must have a maximum step of 15 mm (Approved Document M) to allow wheelchair and walking-aid access (GOV.UK “Approved Document M: Access to and use of buildings” (2026)). Existing homes can use a reasonable adjustment up to 100 mm without full compliance, but any change funded by a DFG must meet the 15 mm standard.
To confirm your eligibility, contact your local authority’s housing adaptations team and request a free occupational therapist assessment. Guide to Disabled Facilities Grant eligibility and application process
The cost of a compliant threshold replacement is around £2,400 — roughly 60 % less than a platform lift. For most homeowners with a single-step access issue, a threshold modification is the most practical and cost-effective solution.
Frequently Asked Questions
Approved Document M sets the maximum step-up at 15 mm for external doors and 10 mm for internal doors in new or replacement doorways (GOV.UK, 2026 edition).
A compliant threshold replacement averages £2,400 including labour and materials, according to the Energy Saving Trust's 2026 home adaptations cost report.
Existing dwellings with a step of 100 mm or less may qualify for a reasonable adjustment without full compliance, as per Approved Document M guidance.
Yes, a threshold replacement costs roughly 60 % less than a platform lift, which averages £6,500 according to DESNZ 2026 cost data.
A threshold replacement is a simpler job removing the old frame and levelling the subfloor, while a platform lift requires structural reinforcement, electrical work, and ongoing maintenance.
