October 18, 2015

All you need to know about Flush Threshold Drainage

Written by Rebecca Clayton

Flush_Threshold_Drain_Blog (4)
A level internal to external threshold at Foxwood A level internal to an external threshold at Foxwood

Creating a flush threshold drainage solution (step-free with no level changes) across the base of rear opening doors is a very popular requirement for modern architectural designs. The inclusion of a level threshold from inside to outside effectively merges the internal and external living spaces by removing that level change.

As attractive as this design element is to modern residential design you must be careful that the opening flush threshold doors chosen are fully designed and capable of dealing with the performance aspects of a level threshold.

One main issue to be thought through is drainage. When your floor effectively continues from outside to inside any openings need to be designed to stop the external elements from crossing that level threshold.

Sliding Glass Doors will give you the highest level of weather sealing whilst creating that desired level threshold. As the sliding door panels sit down into the floor it helps create that weather seal, enabling these large elevations of sliding glass to have very high testing results for water tightness.

minimal windows sliding door drainage detail by IQ Glass minimal windows sliding door drainage detail by IQ Glass

Our minimal windows sliding glass doors already have their drainage options fully thought through with innovative and unique drainage solutions to keep water out.

Beneath the flush threshold aluminium frame sits a solid Neoprene drainage block, running the full length of the sliding glass door elevation. Any rainwater hitting the surface of that glass wall will run down the face of the glazing, into the flush threshold aluminium frame and onto the neoprene block below and is then forced onto the outside, where you want it to go!

From there the rainwater can be fed into our specialist flush threshold drainage channel to effectively move the water away.

Aluminium Bi Fold Doors with Flush Threshold Drain, as seen in Real Homes Aluminium Bi Fold Doors with Flush Threshold Drain, as seen in Real Homes

The problem with most ‘flush threshold’ or ‘invisible’ drains is that they act more like evaporation channels. They create a very minimal appearance but with the UK climate and high levels of rainfall, the water doesn’t get a chance to go anywhere!

A flush drainage channel is a much more effective drainage solution, capable of taking up to 120 litres of water per minute and coming complete with integrated spigots to move water away.

Although most effective with the minimal windows sliding doors this flush threshold drainage solution can be utilised across IQ’s entire aluminium door range, from our ultra slim pivot doors, aluminium bi folding doors and aluminium casement doors.


For more information on specifying glass doors with flush threshold drainage, contact the IQ team today.