Purlin will be in the way of proposed roof window position

[Mr M]

I would like to install a roof window (Velux or Keylite type). I have read in one of Keylite’s brochure’s that in order to comply with means of escape in the event of a fire, the maximum dimension from the top of the existing ceiling joists in what is currently my loft, to the lowest point on the proposed roof window is 1100mm maximum.

The problem I have is that I have an existing timber purlin which is in the way of where the roof window would need to be positioned. See the sketch below. The purlin is 1180mm (to its top) when measured from the top of the existing ceiling joists.

How do I comply with the means of escape in the event of a fire maximum dimension, without having to alter or relocate the existing timber purlin?

Leaving the purlin untouched, I thought about perhaps installing some 75mm cross battens at 90 degrees to the ceiling joists and then 18mm floorboards or loft boarding on top of those but I am then reducing my head height in the loft which I would eventually want to be turning into a habitable room.

Alternatively, could the purlin be cut either side of the roof window and then the 2 cut ends be supported with timber uprights fitted to the purlin down to the ceiling joists.

I look forward to hopefully receiving any thoughts and/or other suggestions.

 

[cdbe]

It's fairly common to install a section of raised floor below the window to reduce the effective height - run it post your BCO.

 

[RandomGrinch]

. I have read in one of Keylite’s brochure’s that in order to comply with means of escape in the event of a fire,

Is this for a new loft conversion, or replacing an existing window?

If the loft conversion would be the second floor of the building, the room would need a protected stairway, to an external door.
An escape window in that case, would not be sufficient and wouldn't be required to comply with regs.

 

[Mr M]

Is this for a new loft conversion, or replacing an existing window?

There are no windows in my loft at the moment but I am looking at having my roof covering replaced in the not too distant future so I wanted to get one or maybe two new roof windows installed during those works. My house has a ground floor, a 1st floor and the loft space above that.

If the loft conversion would be the second floor of the building, the room would need a protected stairway, to an external door.
An escape window in that case, would not be sufficient and wouldn't be required to comply with regs.

I may eventually turn the loft space into a habitable room but I am undecided about that at the moment but I appreciate that those works would be subject to Building Regs approval which would presumably mean having to put a 'proper' staircase in and fit a fire door etc?

I just wanted to make sure that if I had the roof window(s) installed by the Roofing Contractor who carries out my re-roof, that should I decide at a later date to turn the loft space into a habitable room then the height of the roof windows would be compliant.

 

[RandomGrinch]

I just wanted to make sure that if I had the roof window(s) installed by the Roofing Contractor who carries out my re-roof, that should I decide at a later date to turn the loft space into a habitable room then the position of the roof windows would be compliant.

Then yes, you need a protected stairway, or other mitigating factors (sprinklers etc.).
Having escape windows in the loft would then be a moot point.
You may wish to install them for peace of mind, but their height (relating to escape windows) shouldn't be a concern to building control.

 

[Mr M]

So it would appear that the 1100mm maximum height dimension that Keylite refer to does not apply to me, regardless of my two potential situations ie

If I have the roof window(s) installed and I leave it as a loft space then the roof windows can be installed at whatever height above my purlins
or
If I later decide to turn the loft space into a habitable room then the height of the windows does not form part of building regulations as it is the new staircase that would provide the means of escape in the event of a fire.

I wonder what situation Keylite's advices in their brochure would apply to then

View Brochure - Keylite Roof Windows

www.keyliteroofwindows.com

Page 26

 

[RandomGrinch]

I wonder what situation Keylite's advices in their brochure would apply to then

It would be relevant in situations that actually require escape windows - i.e. replacing existing, or a bungalow conversion.

 

[Mr M]

Ok. Thanks for the advice. Much appreciated.

 

[securespark]

I read the thread title as "Putin will be in the way...."

 

[jj4091]

Are the current ceiling joists deep enough to be used as floor joists if you turn it into a habitable room in the future. If they are not then by the time you increase the depth you may not have a problem achieving 1100mm

 

[Mr M]

Are the current ceiling joists deep enough to be used as floor joists if you turn it into a habitable room in the future.

Yes. The joists in my loft are a similar size to my 1st floor joists and none of the joists in the loft span any greater distances than my 1st floor joists.

If they are not then by the time you increase the depth you may not have a problem achieving 1100mm

According to the earlier posts, the 1100mm maximum height dimension that Keylite refer to does not apply to either of my situations ie regardless of whether I leave it as a loft space or if I turn it into a habitable room at some point in the near future as the window installation would not form part of building regulations as it is the new staircase that would provide the means of escape in the event of a fire.

 

[jj4091]

Good, I was just wondering what alternatives you had should the need arise. As cdbe says a simple platform under the window would be another option.

 

[Mr M]

As cdbe says a simple platform under the window would be another option.

Just my opinion but I think putting a raised platform or for want of a better phrase, a step below the window to raise the height in that location may look quite strange and would not be ideal. Nevertheless,

According to the earlier posts, the 1100mm maximum height dimension that Keylite refer to does not apply to either of my situations ie regardless of whether I leave it as a loft space or if I turn it into a habitable room at some point in the near future as the window installation would not form part of building regulations as it is the new staircase that would provide the means of escape in the event of a fire.

But I suppose if an installation did need to comply with Building Regs ie

It would be relevant in situations that actually require escape windows - i.e. replacing existing, or a bungalow conversion.

then to avoid having to raise the entire floor or alter the position of the purlin then this may be an alternative way of complying with Building Regs

 

[^woody^]

Installing a rooflight, irrespective of what you may or may not do with the loft, is controlled work and requires a building regulation application.