Manufacturers, Suppliers and Installers of High Quality
Aluminium and UPVC Windows, UPVC Doors,
Composite Doors, Folding Doors, Double Glazing
and Conservatories since 1988

Aluminium Bifolding Doors Survey Guide

Below is our 10 step guide to measuring your aluminium bifolding doors. If we are fitting your bifolding doors then a full survey conducted by ourselves is included in the price. However if you are purchasing aluminium bifolding doors to fit yourself, then the survey is not included and we would expect you to provide the final manufacturing sizes.

If after reading the guide you are unsure how to conduct a survey, then please contact us as we can provide advice over the phone. If you would like us to conduct a survey for you, then for a small fee we are able to provide this service.

The 10 steps are:

• 1 - Download our Folding Door Survey Worksheet and Order Forms
• 2 - Identify your requirements
• 3 - Check that the opening is square
• 4 - Measure Internal Width
• 5 - Measure Internal Height
• 6 - Measure External Width
• 7 - Measure External Height
• 8 - Determine Required Threshold and Cill
• 9 - Repeat steps 2 - 8 again
• 10 - Complete Order Form

1) Download our Folding Door Survey Worksheet

Please download our Folding Door Survey Worksheet and Order Form. This worksheet provides space for you to record the information you need as part of this survey, whilst the order form has all the relevant options that you need to determine before we are able to manufacture your doors.

2) Identify Requirements

The next step is to identify the style and design of the bifolding doors. For this you will need to consider the following:

• Style - how many segments are the aluminium bifolding doors split into, and which way to they fold?
• Opening direction - do the aluminium bifolding doors open inwards or outwards?
• Hardware colour - What colour are the handles and hinges? (Choose from Black, White, or Chrome)
• Trickle Vents - Does your aluminium bifolding doors need trickle vents (if you are unsure consult your building inspector)

Complete the relevant boxes in the survey worsheet, and draw a picture of the folding doors in the main box. Remember that we view all our items from inside.

3) Check that the opening is square

Folding doors need to be fitted exactly plumb in all 3 axis (horizontal, vertical front to back, and vertical side to side). If the doors are not fitted plumb then they will not operate correctly. Therefore ensure that all aspects of the opening are level and square. If the opening is not level or square then you need to make an allowance in the final measurements so that the bifold door can be fitted plumb.

4) Measure Internal Width

The purpose of measuring the internal width is to determine the thickness of the plasterline. Measure the internal rebate so that this measurement can be deducted from the external width to calculate the thickness of the plaster.

For open out bifolding doors the inside of the left and and right side frames is 60mm thick. Obviously you do not want the plaster to be less than approx 15mm from the inside edge of the frame so if the plaster is more than 45mm thick on either side then you will want to add a build up to the side of the frame.

For open in bifolding doors the inside of the left and and right side frames is 30mm thick. Again you do not want the plaster to be less than approx 15mm from the inside edge of the frame so if the plaster is more than 15mm thick on either side then you will want to add a build up to the side of the frame.

5) Measure Internal Height

The purpose of measuring the internal height is to determine the thickness of the plasterline at the head of the frame and to help identify what threshold is required (see step 7). The same principle applies to the plaster line at the head of the frame as it does for the internal width measurement (see previous step).

If the aluminium folding doors are to be fitted with trickle vents then a 42mm add-on is fitted to the head of the frame. However the vents themselves are fitted approx 20mm from the top of the frame, so the plasterline cannot be any thicker than this.

6) Measure External Width

The external width measurement will determine the manufacturing width of the aluminium folding doors. Take at least three measurements at the top, middle, and bottom of the opening. The smallest measurement will be used to calculate the width. We recommend that you deduct 10mm from the smallest measurement to calculate the manufacturing width.

7) Measure External Height

The external height measurement will determine the manufacturing height of the aluminium bifolding doors. Again, take at least three measurements at various intervals and note down the smallest measurement. We recommend that you deduct 10mm from the smallest measurement to calculate the manufacturing height.

8) Determine Required Threshold and Cill

In order to determine what threshold you require you need to measure the difference in height between the internal floor level and the bottom of the cill. The best way to do this is by using a spirit level across the threshold and take measurements with a tape measure to the internal floor and the bottom of where the cill will sit.

Consult our aluminium folding door threshold page to identify what threshold you require. Remember that you can always lay down a bed of cement under the cill to increase the height of the threshold if the difference between the internal floor level and the bottom of the cill is too much, or alternatively you can always take out half a brick or similiar to lower the threshold if the difference is too little.

At this stage you should also identify what cill you require (if any). Measure the distance from the outside edge of the brickwork to where the back of the frame will sit and allow an extra 30mm for the drip of the cill. Available cill widths are 150mm and 190mm, however in 90% of all installations a 150mm cill is adequate.

9) Repeat Steps 2 - 8 again

It is better to measure twice and make once, than to measure once and make twice. Therefore we recommend you double check all your measurements again before proceeding.

10) Complete Order Form

Please download our order form for Aluminium Folidng Doors. It is better to complete this form and to fax or email this to us to avoid any miscommunication. We can talk you through this over the phone, however we do not like taking sizes over the phone as often these can lead to misunderstandings.

Remember that final manufacturing sizes relate to the overall size of the folding doors that you require us to make. We will make deductions for cill heights, trickle vent add-ons, frame add-ons etc if you have specified them, just provide us with the overall finished size that you require. However you will need to make an allowance for your brickwork clearance from your external brickwork sizes (see steps 5 & 6).