Quick answer
Accessible or 'disabled access' thresholds reduce the upstand a wheelchair or mobility aid has to cross, generally guided by Approved Document M's accessibility principles, while still needing to manage weathertightness properly. A well-specified low-threshold composite door can achieve both, but it needs correct drainage detailing and, ideally, a canopy on exposed Cornish elevations.
Overview
Part M of the Building Regulations sets a 15mm maximum upstand for accessible thresholds. Multiple composite door brands offer compliant options.
Symptoms
- New-build requirement.
- Ageing-in-place adaptation.
- Wheelchair user in household.
What 'accessible threshold' actually means
There's no single fixed measurement that defines an accessible threshold in every context, but the general principle behind Approved Document M's guidance is to keep any upstand as low and as free of sharp edges as reasonably possible, so a wheelchair, mobility scooter or walking frame can cross without a jolt or a trip risk. In practice this usually means specifying a threshold well below the 15-20mm typical of a standard weathertight design.
Approved Document M applies most directly to new dwellings and to non-domestic or communal buildings, but its principles are widely used as good practice when adapting an existing home for a resident's mobility needs, even where it isn't a strict statutory requirement for that specific job.
It's also worth considering the wider approach path to the door, not just the threshold itself - a perfectly specified accessible threshold is of limited use if the path leading to it has an unmanaged step, an uneven surface or insufficient turning space for a wheelchair, so a joined-up look at the whole approach is usually more valuable than focusing on the door alone.
Why this matters for day-to-day independence
A threshold that seems like a minor inconvenience to an able-bodied visitor can be a genuine daily obstacle for someone using a wheelchair or a frame - catching a front castor, requiring a run-up, or simply being tiring to negotiate several times a day. Getting the threshold right is often a small part of a wider access plan for a home, but it's one of the parts used most frequently, several times a day, every day.
Door width matters alongside threshold height for genuine accessibility - a wider clear opening gives more manoeuvring room for a wheelchair or scooter, and it's often sensible to review both together during any adaptation rather than treating the threshold in isolation.
Balancing access with keeping the weather out
The engineering challenge with any accessible threshold is that reducing the physical upstand also reduces the barrier holding back wind-driven rain, so the drainage and sealing detail has to work harder to compensate. BS 6375 governs how doorsets are classified for weathertightness performance, and a genuinely low or flush threshold needs to be tested and detailed as a system - not just a standard threshold cut down - to maintain a sensible weathertightness classification.
This is why we'd always recommend a manufacturer's purpose-designed accessible threshold system over an ad hoc reduction of a standard bar; the drainage channels, seals and any built-in fall are engineered together rather than compromised individually.
Lighting and colour contrast at the threshold also help some users, particularly those with visual impairments alongside mobility needs, so a slightly contrasting threshold strip or clearly defined edge can be a small addition worth discussing during the same piece of work.
Practical measures that help on exposed sites
On coastal or otherwise exposed Cornish properties, a flush or near-flush threshold benefits from additional protective measures that a standard threshold might not need: a canopy or recessed porch to reduce direct rain reaching the door, external ground graded firmly away from the threshold, and a drainage channel or gully set into the paving immediately outside to carry away any water that does reach the doorway.
Where an existing door has an integral step that can't be removed without significant building work, a ramp is sometimes a more practical short-term solution while a longer-term threshold replacement is planned, and it's worth being upfront about that if a full accessible threshold isn't achievable in the initial visit.
- Canopy or recessed entrance to reduce direct rain exposure
- External paving graded away from the threshold, not towards it
- A drainage channel or gully set into the ground just outside the door
- Manufacturer-specific accessible threshold system rather than a modified standard one
What a home assessment for this looks like
A sensible starting point is looking at the existing doorway's external ground levels, the direction the property faces relative to prevailing wind and rain, and how the internal floor level relates to the outside step, before recommending a specific threshold product. Where the internal floor sits well above external ground level, achieving a genuinely low or flush threshold sometimes needs floor build-up changes as well as door changes, which is worth knowing early rather than discovering partway through a job.
It's also worth checking the handle and locking arrangement as part of any accessibility-focused work, since a heavy, awkward multi-point handle can be as much of a barrier to someone with limited hand strength as a high threshold is to someone using a wheelchair, and lever-style or lighter-action hardware is sometimes worth specifying alongside the threshold change.
Funding and wider adaptation context
Accessible threshold work often forms part of a broader set of home adaptations, sometimes supported through Disabled Facilities Grants or similar local authority schemes, which typically require an occupational therapist's assessment before work is agreed. We're happy to work alongside whatever assessment has already been carried out and quote against those specific recommendations rather than starting from scratch.
Where a Disabled Facilities Grant or similar funding is involved, it's often worth involving us early in discussions with the assessing occupational therapist, since specifying the right accessible threshold product from the outset avoids a mismatch between what's been approved on paper and what's practically achievable on the actual doorway.
Maintaining an accessible threshold once it's fitted
Because a low or flush threshold has less margin for error than a standard one, keeping the drainage channel clear of grit, leaves and salt residue matters even more than on a standard door, and it's worth checking more frequently - particularly after storms - since a blocked channel on a reduced-height threshold reaches its limit and lets water through much faster than one with a deeper reservoir to work with.
Seasonal changes are worth planning for too - a threshold that copes well with a dry summer visit from an occupational therapist may behave differently in a wet Cornish winter, so it's worth thinking through worst-case weather conditions during the initial assessment rather than only the conditions on the day of the survey.
Where possible, we'd also encourage a short trial or demonstration of the proposed threshold height using a temporary ramp or ply packer before committing to the final specification, since it gives the actual door user a chance to confirm the height works in practice rather than relying on a plan alone.
Typical repair costs in Cornwall
| Work | Typical price | Notes |
|---|---|---|
| Accessible/low threshold door, supplied and fitted | From £1,395 | Manufacturer-specific accessible system |
| Site assessment for access adaptation | £65-£95 | Often credited against subsequent work |
| External drainage channel/gully installation | £150-£280 | Recommended on exposed elevations |
| Canopy or porch addition | £220-£320 | Extra weather protection for flush thresholds |
Guide prices only — we confirm the cost after seeing the door.
When to call a professional
- For a Part M-compliant replacement doorset.
