There are various advantages to a flush threshold detail for a patio door. When looking purely in terms of design, the absence of frame or structure at the base of the glass doors allows the merging of inside and out to occur even when the glass doors are shut. In many projects it’s difficult to discern from images alone when the glass doors are open or closed. This continuation of building and living space from inside to out is a desirable trait for most modern home projects.

In terms of usability, a flush threshold creates an easier transition between the internal and external living spaces of a building. This can be showcased easily on swimming pool projects where the threshold of the sliding door is likely to be walked over in bare feet. You want this threshold to be flat and level with the floor finishes to ensure this is comfortable for the users.

Flush thresholds have an obvious use inaccessible or inclusive building designs. The minimum window sliding door thresholds have been tested and certified for barrier free access ability which showcases the benefits of its use in a wheelchair or accessible environment. These sliding patio doors have been designed with wheelchair users in mind. A flush threshold allows wheelchairs or other access ability devices to manoeuvre over the frame with no step level change or catches.

You can see this detail used to great effect on the accessible building design for Claywood House. All exterior doors used a flush threshold for wheelchair access within the minimal windows doorways. This allowed the architects to create an inclusive home design for the wheelchair user and their family.

How does a flush threshold patio door maintain weather resistance?

When specifying a flush threshold patio door you want to ensure it maintains its weather resistance even with this flat base design. Sliding door systems have the advantage over bifold doors in this area thanks to the recessed nature of the sliding door pane.

The sliding glass panels within the minimal windows sit recessed in the base frame of the glass doors. This overlapping of frame and glass create the robust weather resistance expected and required of high profile projects. This then allows systems like minimal windows to achieve high levels of water and wind resistance whilst maintaining a completely flat threshold detail. The minimum windows 4+ system for example uses a flush threshold detail and has been tested to hurricane levels of wind and water.

Do flush threshold patio doors include drainage?

One important consideration for flush threshold patio doors is ensuring that drainage is detailed and built into the base frame as standard. When your floor finishes are continuous from inside to outside you need to ensure that water run-off and surface water outside will be dealt with properly. Your slim sliding door system should have built in drainage both within the base frame itself and outside of the flush threshold. The nature of this external drainage will depend on your building project and other aspects of the build however various drainage options are available for the minimal window system that are designed to maintain this flush internal to external design.

Whether you opt for a hidden slot drain or a higher volume external drainage channel, the transition from inside to outside maintains the flush nature and allows for proper water drainage and high levels of rain resistance.