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Fensa Document K – Protection from falling, collision and impact

Hi, I’m Dave Walters of DW Windows and I’m here with this video to try and make sense of the Fensa regulations.

What are the FENSA regulations?

The FENSA regulations came about in April 2002 and are designed to ensure that double glazing companies like ourselves are installing windows in accordance with the current building regulations and standards.

What does that mean for you as a homeowner?

It means that we’ll register your installation with FENSA. We’re approved, so this makes sure the job is done correctly, safely and using the proper materials. Then FENSA will either send you a certificate, which you need to keep as it’s part of your seller’s pack if you’re ever moving to a new house. Or FENSA will inspect the job once it’s been finished or during the installation, this all happens within 30 days.

What is Approved Document K2?

Document K is split into two sections, K2 and K4. Firstly, K2 is about protection from falling from and collision with windows and doors. Falling relates to falls of 600mm or more and to opening windows lower than 800mm from the finished floor level (FFL). So, if you’ve got a window opening lower or within 800mm of the floor and there’s a danger that you could fall out of that, and the fall to the floor on the outside is more than 600mm (or 2 feet), then we need to do something to make that situation safer.

Collision mainly relates to colliding with an open window. So, if a window opens too far and it’s within 800mm of the floor level then there’s a potential for a passer-by to walk into that open window and get injured. Best advice is to fit a restrictor to open windows below 800mm from the finished floor level and we would do that as standard. But there’s a bit of a grey area with this and as long as we’re not making the situation any worse (and this only applies to K2, not K4), we can replace like for like. So, what that means is if the old window hasn’t got a restrictor on then we wouldn’t have to put a restrictor on the new window. Or on the other hand, if we’re changing the design of the window and adding an opener at the bottom, or the old window has got a restrictor on, then it’s best practice to put a restrictor on the new window.

What is Approved Document K4?

K4 is the main one about protection against impact with the glass itself, with the glazing. Any glass within 800mm of the finished floor level (FFL) or within 300mm of a door has to be safety glass. So, that does include high-level glass, top lights and that mainly above 1500mm – I’ll explain that a little more in the diagrams I’ve got at the bottom.

What is safety glass?

It can either be toughened glass, laminated glass or wired glass. What the toughened glass is designed to do is shatter into tiny little pieces if someone did manage to collide with it and break it, rather than get cut to shreds with shards of glass. Wire glass and laminated glass is a lot tougher to break, but if it does it locks together and it doesn’t break into shards – so that’s where you get the safety from, from those two options.

Critical locations

As I mentioned earlier, the 800mm dimension and the 300mm dimension I’ve put on this diagram here. So, basically, any glass within 800mm (which is all this low-level glass) has to be toughened. Any glass within 300mm of the door has to be toughened, but that doesn’t apply to any glass above the door i.e. that top light there – although, within 300mm of the door, it’s above 1500mm so it doesn’t apply to that. And this pane here, the whole of that pane has to be toughened safety glass because part of it is within 300mm of the door. So, you can’t actually toughen part of the glass unit, you have to toughen the whole of the glass unit.

A couple of other areas where people get confused are stairs – the dimension is the same, 800mm, but it’s measured directly down. So, if that side of the window is a metre from that step (but this dimension here is a lot less than that because the stairs are rising), then if any part of that glass is within 800mm of the surface of a step at a right angle downwards then the whole of that glass unit would have to be toughened or safety glass.

Safety glass in bathrooms?

Now the other area is in bathrooms. You don’t always have to have safety glass in bathrooms, the same rule applies; the 800mm from the finished floor level (FFL) and (in this case) the finished floor level would be classed as the actual bottom of the bath where you would stand. So, on here the 800mm from the bottom of the bath is coming half way through that glass unit there – so the whole of that bottom glass unit would have to be safety glass. The top one wouldn’t as it’s above 1500mm and it’s also out of the 800mm danger area. And that wouldn’t be there because all of its above 800mm, so none of that glass would have to be safety glass.

I hope that makes a little bit of sense! If you need any more information you can contact us at or you can give us a call on our freephone number which is 0800 999 0909. So, thanks for listening and I’ll get back to you soon with some more valuable information.

Related to this post:

What are the Fensa regulations?

Fensa Document C – Resistance to moisture

Fensa Document F – Ventilation

Fensa Document J – Combustion Appliances

Fensa Document L- Conservation of fuel and power

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