Meeting the challenge of Part M

Although Building Regulations are notoriously difficult to read, I think there’s a fairly widespread understanding of Approved Doc M across this industry, and how it applies to the door sector in particular. Essentially, it is all about ensuring that there is an ‘accessible threshold’ installed on the principle entrance doorway and all other external doors, including those to and from a private garden, in a new build property or a building which is undergoing material conversion or alteration.

It’s an integral part of the Lifetime Homes standard, which has the very laudable aim of making all new homes accessible to the disabled and those with restricted mobility.

For our purposes, an ‘accessible threshold’ is defined as a 15mm upstand and, while I appreciate that most people do recognise that requirement, I still regularly see examples of fabricators and installers using 20 or even 25mm upstands with ramps incorporated either side to lessen the obstacle, particularly on sets of PVC-U double doors.

While these may be accepted by some Building Inspectors, they don’t actually comply with the letter of the law and they leave any property with a downward sloping approach at risk from water overrunning. Officially, there is obviously nothing to stop an Inspector refusing to pass an installation with an upstand which is more than 15mm.

I understand of course that the reason why some do still choose a higher upstand is that it remains extremely challenging for single and double doors in PVC-U fitted with a low threshold to pass both the weather test contained within BS6375 pt 1 and the security test within PAS24.

I also think that builders should take some responsibility and consider these regulations when designing their properties. Many times I have seen doors fitted with low thresholds that are positioned at the bottom of a slope with no precautions taken to lessen the effects of water running down the slope directly into the door. A simple drain or even a canopy would help!

Mila has recognised this problem and it is something which we have been addressing over recent months in conjunction with one of our key development partners. They have developed a 15mm low threshold with integrated drainage which can be used with any frame system simply by changing the endcaps; and Mila in turn has developed the shootbolt and keeps to work directly with that.

The integral drainage enables the low threshold to meet the BS6375 pt 1 weather test, and our new shootbolt incorporates a sliding keep and static mushroom which fits into the low threshold giving sufficient penetration without the need for drilling any holes and preventing movement of the door when testing. Test doors have been successfully tested to the PAS24: 2016 security standard.
We will be releasing further details of this Part M, Part Q solution next year as part of our ongoing mission to provide an added value service to our customers

We will also be releasing details of a TS008 compliant letter box which overcomes what I see as the other recurring issue of Part M as it applies to doors – namely the fact that there should be a minimum clear width of 775mm.

The 775mm clear width is measured between the inner most part of the frame and the face of the open door and, while door furniture can project into this width, installers must take into account furniture fitted onto the door. What I have seen several times lately is TS008 compliant letterboxes being fitted which protrude by up 80 or even 100mm on the inside of the door, limiting how far the door can swing open and reducing that 775mm width.

Installers need to be aware that, while they might be satisfying the criteria of a security standard on one hand by fitting these letterboxes, they might be failing the accessibility requirements on another.

Fabricators and installers who want more advice on Part M can contact me directly for further advice via: or on Twitter @StraffordCooke

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