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A Guide to Measuring Your Door for Replacement

If your door is looking a little tired and weathered, you’re probably thinking that it’s time for a replacement. Before you head out in search of a brand new door, it’s important to make the right preparations ahead of your hunt. This will ensure that you invest your time and money in a door that’s right for your home and saves you a lot of hassle that you’d have from purchasing an ill-fitting replacement.

One of the more crucial elements to finding the ideal replacement door for your home is ensuring you have the right measurements for it. In this quick and simple guide, you’ll find out exactly what needs to be done to measure your door in preparation for replacement.

The measurement process

You will want to take measurements of both the height, width and diagonal of your door frame. The measurements you will want to take have been highlighted in our diagram.

where to measure your door

Width (red): We suggest that you measure at 3 points. The measurement you want to give is the smallest minus 10mm.

Height (yellow): We suggest that you measure at 3 points. The measurement you want to give is the smallest minus 10mm.

Diagonal (blue): By measuring the diagonal you can ensure the opening is square. These measurements shouldn’t be more than 5mm different. If they are we would recommend seeking help from a professional.

Top tip: Many suppliers tend to use mm as opposed to cm, to optimise the accuracy of their measurements.

If your door has a cill

If your door has a cill included then this will need to be included within your height measurement. Cills are usually a standard size of 30mm.

You need to measure inside and out

The outside and inside measurements are likely to differ. This means that further considerations may need to be taken into consideration when ordering your door.

  • In an ideal the inside measurement should be slightly smaller than the outside measurement but the frame should still be able clear the inner plaster line. In this case no extra considerations are needed.
  • If the difference is larger and there isn’t enough room you will need to have an addon for your door. This is an extra measurement between the your outer brick and plaster line.
  • In some circumstances you may have a “box sash“ scenario where the inside measurement is greater than the outside measurement. For this you will need to take the brick to brick measurements and then add 5-10mm each side to ensure that the frame sits behind the brickwork.

With the right planning and preparation beforehand, purchasing and installing a new door shouldn’t have to be difficult. With this simple guide and these quick and easy preparations, you’ll save yourself a lot of time and effort, by finding the ideal replacement door from the off.

Please note this is only a guide to help you measure the dimensions for your new door. We do not accept any liability for any errors in measurements you may make. If you are struggling with the measuring process we would recommend hiring a professional to do this for you.

We offer a huge range of composite doors with over 20 styles in 30 different colours
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