There are 3 key steps… and it’s as easy as 123…
- Plan as early as the concept stage
- Know the door system threshold profile
- Know the final internal floor finish level and external level
How Marlin can help you
We make it simple to get it right… as simple as ABC…
- A. Marlin experts liaise with you at the concept and early planning stages so that every detail is accounted for to make sure that everything is fully considered and nothing is overlooked.
- B. Marlin provides a free sample of the door system threshold profile for your planner and builder to work from.
By using the sample you will know exactly how to set the masonry at the correct height to support the threshold and achieve a low or flush appearance.
There’s nothing quite like having the actual threshold profile to work with.
- C. Visit the Marlin showroom to see a demonstration of all the elements required to achieve a low or flush threshold - you will see exactly how to prepare for the very best outcome.
Early planning to avoid disappointment and unnecessary expense
The way we achieve the desired threshold height between the inside and outside of bi folding or sliding doors is to plan for it in advance before the build is 'out of the ground'.
Early planning will avoid accepting a disappointing ‘step over’ threshold and prevent unnecessary expense caused by remedial work to rectify masonry that is set to the wrong height.
Three and four track sliding doors have deep thresholds and it is vital that the floor structure will accommodate this detail.
Know the door system threshold profile
The builder needs to know the exact height and depth of the threshold profile in order to set the masonry at the right level and ensure there is enough support for the door. Knowing the depth of the threshold profile he will be able to accommodate for any overhang into the cavity area.
The builder will also be able to decide the correct size of damp proof membrane to go under the threshold profile and ensure that this is installed correctly to provide necessary damp protection.
So how does the builder know the exact height and depth of the threshold profile? Simple. Marlin provides a free sample of the chosen bi-fold or sliding door system threshold which allows the builder to work with a physical piece of the actual profile. The sample can be placed in the ground and worked with to fully understand the relationship between the height of masonry that will support the threshold and internal and external levels.
Know your levels
In order to achieve the desired threshold height it is vital to understand what the final levels will be on both sides of the door. The final floor finish level will dictate the masonry height on the external leaf of the building that is supporting the door.
the final floor finish must be known - This is the surface that will be walked on e.g. tiles, laminate flooring, wood flooring, carpet etc. - factor in any allowance for any screed, adhesive or underlay that may be used beneath.
The level quality of the final floor finish will dictate the connection accuracy with the threshold so it is important to spend some time on this detail. For open in bi fold doors, make sure that the final floor finish is level in all directions under the area in which the door panels open.
Bear in mind that a 100% flush threshold is hard to achieve, especially on larger spans. This is because all final floor finishes, almost without exception, have some level variations.
To help accommodate for slight level variations we recommend aiming for a small threshold upstand above the final floor finish. This will create an opportunity for a neater connection detail when sealing or grouting the final floor finish up to the threshold. Also, if textured tiles or flagstones with heavy surface irregularities are to be used a small upstand will more easily accommodate for this.
For open in bi fold doors a small upstand will provide necessary panel clearance – please see below.
the threshold incorporates a drainage system with an outlet on the outside face – the out- let cannot be blocked under any circumstances. As such, steps, paving flags or decking must approach the outside face of the threshold so as not to block off the outlet.
With a sample of the threshold profile on site the builder can work out the height of the masonry that will support the door threshold and the position of the threshold within the reveal area.
For new floors, the threshold profile sample will also help to establish the edge of the floor structure.
For existing floor structures, the threshold profile sample will help to understand if there is a positioning issue within the reveal area and is a guide to establishing any necessary modifications to existing timber joists and flooring particularly when installing a three or four track sliding doors.
Allowing for clearance
Open In Bi-fold Doors
As explained above, a small threshold upstand is advised to accommodate small level inaccuracies but is also vital for open in bi fold doors to ensure that the panels will fully open.
Looking out on an open in bifold door low threshold
Looking in on an open in bifold door low threshold
Looking out on an open in bifold door low threshold with cill
Looking in on an open in bifold door low threshold with cill
This is very important for a number of operational reasons:
- To accommodate for minor level inaccuracies
- Prevent panels from binding on surface bumps
- Ensures unhindered, smooth and effortless operation
- Avoids dislodging panel sealing gaskets
Open Out Bi-fold Doors
Allowing clearance under the panels is not usually necessary since most external levels finish lower than the drainage outlet on the outside face of the threshold.
Looking out on open out bifold door low threshold
Looking in on an open out bifold door low threshold
Looking out on an open out bifold door low threshold with cill
Looking in on an open out bifold door low threshold with cill
However, when using a rebated threshold some design requirements indicate a minimum step between inside and outside. To achieve this, the external finish would then approach the threshold above the drainage outlet and so for this detail the same panel clearance rule will apply as for open in bi fold doors.
The sliding and fixed panels do not overhang the outside faces of the threshold on the inside of the room so panel clearance is not required.
For this reason the final floor finish can be built up to the top of the threshold to achieve a flush finish.
However, as previously explained don’t forget about the connection detail between the finished floor level and the threshold and any level irregularities that can be usefully accommodated for by creating a small upstand detail.
Allowing for drainage
The door framework is designed to drain water. It is vital that the drainage holes on the outside face of the threshold are not blocked by masonry, steps, paving flags or decking etc.
For materials that are close to or touching the threshold above the drainage outlet on an installation at ground level, make sure that adequate land drainage is in place. This can be a simple channel filled with a coarse aggregate or an ACO type drain - installed with careful planning this can be discretely hidden under external finishes.
For an installation onto a balcony area, make sure that an adequate drainage system is in place under any external materials that are close to or touching the threshold above the drainage outlet.
Bifold Door Drainage Open In
Bifold Door Drainage Open Out
Bifold Door Drainage Cill Open In
Bifold Door Drainage Cill Open Out
Marlin provides threshold profile samples to help with construction details and surveying decisions. This is a free service for all orders and can be invaluable in helping to clearly understand the relationship between the masonry that supports the threshold and the final floor finish.
What the builder needs to know
At the start of the project the builder needs to know the following important information:
- The door system and design
- Panel opening configuration
- Threshold design
- The target height for the threshold
The builder will create the new opening and lay masonry to support the threshold. The height and level accuracy of the masonry will dictate the height of the threshold in relation to the final floor finish.
With the final floor finish known and the threshold profile sample on site you can be confident in achieving the required threshold detail.
It is possible that the existing floor structure will need to be modified in order to accommodate the depth of the threshold profile.
This is usually the case for deep three and four track sliding door frames but can apply to other frames depending on the desired position of the frame within the building fabric.
The Marlin Showroom
Please visit our showroom in Keighley, West Yorkshire for a full demonstration of a bi fold or sliding door that has been correctly installed into a low or flush threshold environment.
Our knowledgeable and friendly team of experts will explain everything you need to know in order to achieve the very best design, function and installation results.
What to do now - Talk to us
Marlin have years of manufacturing and installation experience and are here to share this with you.
As soon as you have a concept please get in touch to discuss your project - we will guide you through the entire process, help you to avoid all of the common mistakes and ensure you achieve the best possible results.
If like us you want to achieve the seamless appearance of a low or flush door threshold then leave nothing to chance. Talk to Marlin now! Call 01535 603909 or click here.
See more pictures to inspire in our door galleries: