Tips and Advice for low thresholds on sliding patio doors

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Nick Dardalis

What is the best way of achieving flush or low thresholds on sliding patio doors?

Unlike a bifolding door, sliding doors do not normally protrude over the threshold or frame on the inside or outside of the doors. This is because sliding doors do not move along their track and don’t project in or out like hinged doors. As a result, you don’t need the clearance and free space hinged doors need to rest in the open position.

Therefore it is entirely possible to achieve a flush floor finish with a sliding door. However, you will need to consider the threshold detail at the design stage.

low thresholds on sliding patio doors showing the sunvista model in a new home
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Low thresholds on sliding patio doors for new extensions.

For new extensions knowing the sliding door system you are using, the internal and external levels you wish to achieve and communicating this information to your builder is a must.

Having the right information at the design stage will ensure you not only get the floor level you require but avoid having to make adjustments and compromises after the sliding doors are fitted.

Low thresholds on sliding patio doors in existing openings.

If you intend to have new sliding doors in an existing structural opening, it is still possible to achieve a low and flush threshold. In many cases work needs to be done to the existing floor levels so they can collaborate with the depth and height of the sliding door track profile.

A sliding patio door will usually have a deeper frame than a French door. Typically the depth of an existing door frame is between 70mm and 80mm. Sliding doors with a triple track can be more than double this depth. Your builder will therefore need to make suitable provision that the existing floors and walls can accommodate this deeper door profile.

Your sliding door installer is there to help you.

A reputable and knowledgeable company supplying a range of sliding doors should be able to help you achieve the desired floor level and the correct low thresholds on sliding patio doors. They can work with you and your builder to ensure all details are covered and checked before any doors are ordered.

If you need a sample of the sliding door track or cill profile, there is no reason why this cannot be provided. Even if this is difficult, all sliding door systems come with detailed technical manuals, providing full-size section drawings and dimensions of typical sections allowing for a variety of site conditions.

Drainage to the outside is very important with low thresholds on sliding patio doors.

All sliding doors are designed and made with drainage holes and slots to enable any water to drain to the outside. Whether your sliding door needs to sit on an aluminium cill is established at the time of the survey. All aluminium systems are designed so that any water that does get in drains away to the outside.

Your builder and sliding door installer should be well aware of this drainage requirement, advising you that paving slabs, floor tiles or decking can meet the front face of your doors or door cill but not obstruct the drainage facility.

For existing structural openings knowing the depth and height of the sliding door track and cill can help your builder position the doors correctly in the aperture to allow for the position of the new DPC (Damp Proof Course) and the position of the sliding door in the aperture.

Our top tips for achieving a flush sliding door threshold.

  • Make sure your builder is aware of what sliding door product you intend to use.
  • Ensure your floor can accommodate the deeper sliding doors having three or more tracks.
  • Your builder needs to know the depth and height of the sliding door track being used.
  • Know in advance the final finish you want on the inside and outside and communicate this to your builder.
  • Talk to your local sliding door installer and ask questions.
  • Ensure you receive a copy of the final survey before any sliding doors are ordered for manufacture.
  • If you change any aspect of your build, let your builder and door installer know.