Design Considerations

How to choose the right bifold door

Choosing the right bifold door

If you’re wondering how to choose the right bifold doors that work for both you and your home, there are a few design considerations that you might want to take into account before deciding on which design of bifold door is the perfect one to meet your needs.

Bifold Door Design Considerations

Opening direction

The first and most fundamental choice to be made is your bifold doors opening options, and whether you want your doors to open outwards or open inwards. Bifold door configurations work both ways, however having your bifold door open outwards is by far the most popular opening option and is advised in most normal circumstances.

Open bifold doors present various issues, such as they take up space within the room when they are folded open, and if wet, they can drip water onto internal floor coverings. They are also more prone to leaking at the bottom should there be significant natural movement of the timber or if the doors slightly warp away from the frame gasket. Open inward bifold doors also have an additional pull handle routed into the visible internal face of each odd numbered door to facilitate closing. These are not required for open outward doors.

Configurations (general)

The total number of bifold doors and configuration type (how many fold left and how many fold right) is the next thing to think about.

When we talk about configurations in terms of the type (odd / even etc), and how many doors in each stack (left and right), they are always referred to as if you are standing on the outside looking in.

Standard sizes for bifold doors – the total number of bifold door leafs and overall frame size possible is partly determined by the total wall aperture width, and the configuration type chosen. Broadly speaking, the maximum door leaf size is 1000mm wide x 3000mm high. So if you’re wondering what is the smallest opening for bifold doors, the minimum widths vary with the configuration.

Bifold doors for small openings – bifold door sets that have only even stacks of bifold doors will not be able to have door leafs as narrow as other doors. This is due to the cam effect of opening the doors, which causes them to bind. Please see separate drawings for more details.

Whether or not you have an access door and therefore easy access from the inside and outside is a primary consideration. Please see the configuration type guide below for details on how to achieve this.
The most practical configuration type is an ODD / ONE, where one of the stacks is ‘ODD’, and the other is a ‘ONE’ (single door). The access door is the single door as default, and this means it can have a standard handle without colliding with any adjacent doors. The other stack (ODD) then also has a free swinging leaf, so that along with the access door it creates what is effectively a pair of double doors.

Configurations that have an access door at the end of an ODD stack (more than one) will have a standard lever/lever handle and will not fold open fully parallel with the other doors as the handle will obstruct this. In this case an extended magnetic catch will be fitted to prevent it colliding. Alternatively, the external handle and lock can be omitted, but then there will be no access possible from the outside. This must be specifically requested if desired.

Configurations that are possible but not as advisable are EVEN / ODD or ODD / EVEN. This means that one stack is ODD (including single) and the other is EVEN. The end bifold door of the even stack will require a small rebate on the face of the timber at the top and bottom to prevent the door dragging the gasket when opened (due to the cam effect of the additional width of the rebate timber).

On configurations that have an access door, the meeting door stiles will be 12mm wider than the other stiles because they overlap (rebate together). Access doors on the end of a set that has an odd number of doors and that all slide one way will have a small angled leading edge to facilitate closing.

Note that the bifold doors shown on the configuration type drawings show open out, but the same applies for open in (as do the door gaps).

Locks

The lock used in all of our bifold doors is an espagnolette type with a euro cylinder lock barrel. On door sets where the door leaf is 1934mm high or more, the lock will have three locking points. On a standard frame setup, this means the frame height is 2050mm high or more. Door leafs under this height will have the same lock, only smaller, with one central locking point.

Both locks operate on a standard door latch which is operated by pressing the handle down to open the door. The locking points are locked by lifting the handle, then turning the key. They are unlocked by turning the key, then pressing the handle down.

Operation is the same from the inside and outside. However, a thumb turn knob can be specified for the internal lock as an optional extra. This eliminates the need for a key to lock and unlock the doors from the inside. A key is still required for operation from the outside.

Handles

The default handle for our bifold doors is a standard espagnolette compatible handle. On certain door configurations this does not pose a problem.

However, on other configurations it can collide with adjacent doors when open and prevent the access door from folding back fully parallel. In this instance an extended magnet keep will be fitted.

Where full folding of the access door cannot be achieved with a standard handle, the external handle and lock can be omitted, but then there will be no access possible from the outside. The latter only solves the problem on open out sets.

You can request that we do not fit a handle, and you can choose your own, as long as it is compatible with our lock (92mm centres), and the base is no wider than 40mm.

If anything other than our standard handle on the inside and outside is required, you must specifically request this in writing.

IMPORTANT NOTE: Some of the drawings and details in this information pack list or show the option for a low-projection door handle, however this option is NO LONGER AVAILABLE due to quality issues.

Shoot Bolts

Every odd numbered door will have a finger operated shoot bolt at the top and bottom internally. The bottom bolts are lockable using the keys provided. The top bolts vary in length depending on the frame height so that they are always reachable for an average height person. Please see additional drawing for more details.

If you require a different length top shoot bolt to that fitted as default, from the standard lengths available, please make sure you specifically request this in writing.

Master door

Each configuration type has a default master door where there is a choice of two free swinging leafs (see above). On bifold door sets where there is a single door, it will be the master. On ODD / ODD sets it will be the left door.

These can be changed upon request, but it may cause issues with the handle type (see below).
All standard drawings are shown with the default master door. If it is changed then the handle position and rebate direction will be opposite to those shown.

Sill / threshold types

There are many different bifold threshold options depending upon what you are trying to achieve with floor levels etc. Full details can be found in our cross section drawings.

Level threshold detail bifold doors – a totally flush floor level from the inside to the outside can be achieved. However, the door bottoms will then only be weather sealed by brush strip. It is only really recommended for sheltered locations. We advise having our 18mm rebate option which seals the door’s bottom and gives them something to positively close against. This is almost flush with only an 18mm change in floor level from inside to outside.

Please see our cross section drawings for more details.

To minimise the overall effective step over height of the threshold, a course of bricks can be removed to allow the threshold to sit lower, or the floor levels can be built up to suit.

Bifold door sill detail – if our extruded aluminium sill is used, then it is self draining (depending on the configuration of the wall aperture). Depending on your site requirements, you may need us to remove one of the sill flanges to facilitate easy installation. You must notify us before we commence manufacture. This can also be done on site with a jigsaw and a metal cutting blade suitable for aluminium.

If a timber frame bifold threshold option is chosen, shoot bolt keeps will be supplied loose. Once the doors are installed, these must be marked, recessed and secured to the threshold in the suitable positions to suit the door bolt locations. The customer / installer must also make their own adequate provisions for drainage. Any holes drilled through the timber must either have a tube inserted or be surface sealed to prevent uptake of moisture into the timber.

Depending on what you are trying to achieve, the aperture height can be specified to us as either the total height, or from the underside of the top of the aperture to the top of your desired finished floor level. We will then add the necessary amount to the frame height to allow for our sill. You must notify us which measurement you have provided and, if required, make your own provisions for accommodating our frame sill within your aperture / floor level.

We can supply no threshold at all if you’d prefer, only the bottom plastic running track for you to set into your own floor. The centre of this should be offset from the centre of the top track by 19mm towards the frame gasket (see cross section). It should be securely fitted as there will be a lot of lateral force on it when the bifold doors are open. Provisions for drainage should be made on site. We can leave the frame jambs over length to be cut to suit your floor level. If they are cut then they should be end grain sealed before installation.

Gear

The handles, catches and running gear are available in various colours. Satin chrome is the most common, followed by polished chrome and polished brass. Other colours can be achieved by powder coating, but this increases the lead time and cost, and reduces the durability compared to the metal finishes. Some functional or non visible components will be a raw metal colour no matter what colour is chosen.

Aluminium Tracks

The top and bottom aluminium tracks are silver anodised as standard, as silver is a nice neutral colour. Different anodised colours such as gold or black can be specified. Any other colour can be achieved by powder coating, but this will reduce the durability of the finish. Changing the aluminium colour in any way will significantly increase the lead time and cost.

Glass

All door sets are factory glazed with 28mm (4 – 20 – 4) double glazed units as standard. Various glass specifications are available at an additional cost. Please enquire at the time of quoting for our standard glass spec and U-values etc.

We can incorporate triple glazing at an additional cost. This then means that integral blinds are not possible within the glass.

We glaze the door leafs at the factory to avoid tricky site glazing, and to ensure they are glazed in optimum conditions. However, this does make the doors heavier (especially triple glazed) and slightly more difficult to install – especially on larger doors. If you would prefer that we send the glass and glazing bead separately, please request this. You will need to source your own glazing pins if this is the case. On painted doors our glazing bead is made from an extruded timber / resin composite material, which reduces movement and increases the lifespan. On stained doors they are made from timber.

Glazing bars, rails and panels

Doors are fully glazed as standard, meaning it’s one clear glass panel.

Various glazing bar designs, mid rails and panels are available at an additional cost. Please enquire.

Glazing bars are available in two types: integral and plant-on.

Integral means they are the full thickness of the door and actually divide the aperture, thus creating separately beaded individual glass units.

These are much thicker and significantly more expensive than the plant on bars. The minimum visible dimension is 48mm.

Plant on means that there is only one glass unit, and the bars face fix to it using adhesive tape. There are integral spacer bars between the two panes of glass of the double glazed unit to give the effect of individual pieces of glass. These are much thinner and more cost effective than the integral bars. On painted doors our plant on glazing bars are made from an extruded timber / resin composite material, which reduces movement and increases the lifespan. On stained doors they are made from timber. The visible dimension is 24mm and cannot be changed.

Timber sizes

The standard sizes for bifold door component sizes are as follows. The visible width is the first dimension and the front to back depth is the second dimension:

  • Frame jambs 68mm x 142mm
  • Frame head 68mm x 142mm
  • Frame sill 68mm x 142mm
  • Door stiles 68mm x 68mm
  • Door top rail 68mm x 68mm
  • Door bottom rail 68mm x 68mm
  • Glazing bars Refer to above

The frame head visible dimension is not changeable. The frame sill visible dimension will vary depending on the type chosen.

The frame jambs can be increased (not decreased) if required to accommodate render, plasterboard, dado rails, skirting boards etc. Please specify if required. This will involve an additional cost and will slightly affect the minimum / maximum frame widths listed above.

The door stile and rail visible dimensions can be increased (not decreased) if desired. Please specify if required (ask us for other available standard sizes). This will involve an additional cost.
Door stiles on rebated meeting doors will be 12mm wider than the other stiles.

Blinds

Integral venetian blinds are available at an additional cost. These sit between the two panes of glass of the double glazed unit.

A choice of colours is available. They are operated using a ball cord that is located on the outside of the glass. The slats can be tilted or the blind can slide up and down using this cord.

When fully retracted they obscure a portion of the glass at the top, and therefore slightly reduce the amount of light coming in.

Magnets

The door leafs have magnetic catches located where appropriate to hold the magnetic bifold doors in position when open.

On access doors on the end of an odd stack with multiple doors that have a standard handle, an extended magnet catch is fitted.

Please note that due to slight timber movement, both top and bottom catches may not contact and only one will be effective. The magnets are not designed to be windproof so should not be used in windy conditions.

Trickle vents

Trickle vents may sometimes be required to satisfy building regulations. It is the responsibility of the customer to check these and specify if and how many vents are required.

Each trickle vent is available in two sizes, 2000mm² and 4000mm². The outer grille will change size but the inner piece is only available in one size.

The vents are located in the door leaf top rail (see separate drawing). There can only be a maximum of one vent per door leaf.

Additional rows of gear

Bifold door sets with a frame height of 2517mm and over, will have an additional row of central hardware instead of the usual single row. However, there will always only be one central lock handle (depending on configuration) regardless of frame height.

On bifold door sets that open inwards, there will be an additional row of internal pull handles.

Stack widths and projections

If you’re wondering how thick are bifold doors? The greater the number of doors in a stack the greater width they will take up when open, but the less they will project. Fewer doors will take up less width but project further. This all depends on the number of doors in each stack, the total number of doors, and the overall frame width.

Details are available on a separate drawing, but here is a rough summary guide (assuming standard jamb widths used):

STACK WIDTHS (DIMENSIONS SHOWN FROM OUTER EDGE OF FRAME TO EDGE OF DOOR)

(JAMB WIDTH -9MM) + (NUMBER OF DOORS X 84MM) or:
Door 1 143mm
Door 2 227mm
Door 3 311mm
Door 4 395mm
Door 5 479mm
Door 6 563mm
Door 7 647mm
Door 8 731mm
DOOR PROJECTION (DIMENSIONS SHOWN FROM OUTER FACE OF FRAME TO EDGE OF DOOR)
Approximately ((FRAME WIDTH – 100MM) / NUMBER OF DOORS) – 50MM

Installation tolerances

We will leave a 10mm overall installation tolerance as standard (5mm on all sides). This means you provide us with your tight aperture dimensions and we will make our outer frame 10mm smaller to aid installation.

If your aperture is particularly uneven, or you feel you require a greater tolerance for any other reason, please specify this before we commence design and manufacture of your doors.

After installation, any gaps around the frame should be covered with mastic or trim (not supplied) for a neat look and to achieve weather tightness.

Frame joins

On frames over certain widths there will be joins in the frame head and sill due to the limitations of material length availability. These will be in the aluminium and / or timber. The location of the joins will vary depending on the door configuration and frame width, and will be at our discretion. The joins will be visible once installed. These joins will also involve an additional cost.

Joins in the aluminium sill should have mastic applied to the meeting faces before being butted together and joined to prevent leaks.

Additional frame to aperture fixings should be located close to the ends of joining components to ensure they remain firmly in line during operation of the doors.

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