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Three tips for working with the 10MB attachment limit

by on November 27, 2019

As of September 2019, we have increased the attachment size limit for supporting documents from 5MB to 10MB. We’ve noticed that a previous article providing guidance about uploading supporting documents is still popular, so have taken the opportunity to update it in line with our current service.

1.  File size reduction/compression 

When submitting your planning application, there are some key things to keep in mind to help speed up the process, resulting in applications being potentially validated by local planning authorities (LPAs) much faster. This includes ensuring that when submitting a supporting document that the correct document type is chosen and is clearly named to explain what the content is, especially for plan types not listed as document types on our website.

This immediately communicates the document type and filename to LPAs, enabling them to index the supporting information more quickly and efficiently.  

The majority of supporting documents (D&A statements, Environmental Impact and Transport assessments etc.) are created in Microsoft Word and include photographs, graphs and other images, before being converted to a PDF format.

Word is often set up by users looking to create print versions of documents so all images are saved at a resolution appropriate for a high-quality print i.e. 300 pixels per inch or higher.

This may result in attachments that are over the 10MB limit. Documents with resolutions of 72 pixels per inch are perfectly adequate for LPA needs and show no detectible reduction in quality when displayed on the LPA website.

Guidance on how to use the facilities built into Microsoft Word to reduce the resolution of images in documents and so minimise their file size can be found on the Portal.

In many cases, this will reduce the file size below the 10MB limit. Documents can also be reduced by converting them to PDF prior to attaching them to your applications. If you have already reduced the file sizes in Word then PDF reductions will be even smaller.

2.  Convert documents to PDF

In addition to reducing file size, PDF is a widely accepted file format and commonly used by LPAs when publishing application documents on their websites.

Converting supporting documents to PDF prior to submitting them helps to minimise the risk of delays caused by LPAs having to convert them prior to publication.  CAD drawings converted into PDF should be created in landscape format to ensure the correct orientation for on screen display. Converting documents in this way ensures the quality of attachments is maintained when displayed by the LPA and adds a degree of security that prevents changes being made to your documents once submitted. These were once concerns for users when we introduced digital planning.

More recent versions of Word will allow you to ‘save as’ a PDF file type. Failing that, free software to convert any document type to PDF can be downloaded from various sources including:




Adobe offers measuring tools to help annotate your applications, including grids to accurately line up text and objects in a document, ruler tools to check the size of objects featured in a document and cursor coordinates.

This helps cut out the need to print documents in order to perform any of these activities. This also supports detailed electronic consultation letting LPAs save time and money by not having to print, pack and post paper copies to consultees.

3. Avoid merged plans and drawings

Prior to being able to submit applications online, many applicants used to (and in some cases still do) include several images on A1 or A0 paper (e.g. site location and block plan, existing and proposed elevations etc.).

This was done to minimise the volume of paper involved and give recipients the convenience of viewing multiple images at the same time.

However, at the Portal we have always recommended limiting the number of plans and drawings to just one per page on smaller paper sizes (preferably A4 or A3 for smaller images).

This has several advantages, in addition to reducing the likelihood of these documents exceeding 10MB, most of the planning officers, staff and consultees who may need to print a copy have access to print A3 paper sizes using an office desktop printer rather than sending them to a large scale printer/plotter that may be located on a different floor or even building.

Meanwhile, those who prefer working with digital images can, depending on the software used, view multiple drawings at the same time and use on-screen facilities to pan around and zoom into images for closer inspection and also annotate them.

LPAs and statutory consultees are increasingly investing in providing staff with dual monitor displays to facilitate this.

We recognise there will be instances where some attachments are still going to be too large to submit online despite following these recommendations.

While very high quality/resolution, complex and multi-colour plans and drawings may be essential for clients and marketing purposes, they often far exceed the needs of planners and consultees to determine planning applications.

It may therefore be worth consider submitting lower resolution documents for planning approval purposes and retaining the higher quality versions of these documents for all other purposes.

If you have any other tips or advice that works for you, please add a comment below.

  1. Whilst this may well help uploading images and enable LPA’s to process applications quicker, most applications will then reach a grinding halt with most LPA’s not having enough experienced planning officers to deal with applications in a timely manner; and certainly not deal with them on time!

    As for various political parties currently claiming large numbers of new houses will be built and having aims and aspirations to do so, they will need to ensure planning departments have enough staff to pass the applications for those houses.

    Am I alone with the LPA’s that I deal with, or is the same widespread across the country?

    • arnold gilpin permalink

      I am afraid it is a common complaint as are inconsistent planning decisions.

  2. Printed drawings often need to be at A1 size on the building site otherwise the text can be too small to read. Planning and Building Control are often happy to print at A3 as they mainly look on screen.I have found it helpful to annotate the drawing to say – 1:50 at A1, 1:100 at A3
    Then it can suit everyone
    Clive Wilson

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