Bifold Door Thresholds Explained: Weathered, Flush and Mobility Options
The threshold is the least glamorous part of a bifold door, yet it quietly decides how well your doors keep out rain and draughts and whether you step or stroll from kitchen to patio. Bifold door thresholds come in a few different forms, and choosing the right one early saves a lot of compromise later.
In this guide, our team explains each option, how drainage works and what to ask before your doors are made.
What is a bifold door threshold?
The threshold is the track at floor level that the door carriages run along as the panels fold. Its design affects weather protection, ease of use and the look of the finished opening.
Because it sits where inside meets outside, it has to work with your floor build-up, patio and drainage. That is why we discuss it at the first survey, not once the doors are on order.
The three types of bifold door thresholds
The Origin bifold doors we install offer three threshold choices, each balancing level access against weather performance in a slightly different way.
Weathered (rebated) threshold: a small raised lip that the bottom door seal compresses against, creating a weather-tight seal.
Non-weathered (flush) threshold: a track set into the flooring so the floor runs through at one level.
Mobility threshold: a low-profile option for easier access, available on Origin's single and French door designs.
Weathered thresholds: the best choice for most gardens
For doors that open onto a garden and face the British weather, a weathered threshold is our standard recommendation. The rebate gives the seals something solid to press against, which stops wind-driven rain and cold air finding a way in.
It does not have to mean a clumsy step. The track can be recessed into the floor so the upstand from outside to inside is just 14mm. If you have been searching for low threshold bifold doors, this is usually the answer.
When a flush bifold door threshold makes sense
A flush bifold door threshold creates a truly flat floor, ideal for households with toddlers, older relatives or anyone with limited mobility. It also gives the cleanest possible look.
The catch is weather performance: with no lip for the seals to compress against, Origin is clear that optimal performance cannot be guaranteed. We suggest flush thresholds for:
Internal openings, such as between a kitchen and a garden room.
External doors sheltered by a canopy, balcony or deep roof overhang.
Openings where level access is the overriding priority and you accept some added risk.
Drainage and keeping water out
Any external bifold needs drainage so rainwater cannot collect in the track. Both main methods work with weathered and flush thresholds.
Face drainage
Water collects in a lower chamber of the track and exits through capped holes in the outer face. A channel drain is usually set in front of the door to carry it away.
Concealed drainage
Water passes from the bottom track through the thermal break into the cill, then out from underneath its front edge, keeping the outside face of the frame clean.
In water tightness testing, Origin bifold doors have withstood pressure of up to 600 Pascals. When bifolds do let water in, the cause is often the installation rather than the product: an unsupported threshold, unplanned levels or blocked drainage outlets.
What to ask your installer
Before you sign off on a design, ask:
Which threshold do you recommend for my opening, and why?
How will it sit against my finished floor and my patio?
Which drainage method will you use, and where will the water go?
Who co-ordinates floor levels between you and my builder?
To keep the track running smoothly, vacuum out grit every few weeks and keep drainage slots clear, especially in autumn. For locks and hardware, our guide to making your home more secure through the darker months covers the features worth looking for.
Frequently asked questions
What is the best threshold for bifold doors?
For most external openings onto a garden or patio, a weathered threshold is the best all-round choice. It can be recessed to leave an upstand of just 14mm while still giving the seals a solid lip to seal against.
Can you have completely level bifold doors?
Yes, with a non-weathered flush threshold set into the floor. Weather performance cannot be guaranteed with this option, so we usually recommend it for internal openings or sheltered doors.
Do bifold doors need a drain in front of them?
Most external bifold doors benefit from one. With face drainage, a channel drain in front of the track carries water away, while concealed drainage releases it discreetly from underneath the cill.
Get expert advice on your bifold doors
The right choice among bifold door thresholds depends on how exposed your opening is, who uses it every day and the look you want. Our team will survey your space, work with your builder on levels and recommend the option that suits your home. You can also explore our aluminium door range.
Book a free consultation and we will help you get the details right from the start.
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