Boarding shallow loft above kitchen extension

[Dirtbike123]

Hi,
Looking for a little advice on boarding the loft space above the kitchen extension, single storey with a pitched roof that runs across the entire rear of the house,

Access is through a small door upstairs, so relatively good access so shouldn’t be too complicated.

The joists are 6x2 at 400mm centres, the cabling for all of the down lights have been run straight over the joists and amongst the insulation.

I reckon there is about 200mm of insulation currently, which leads to my dilemma...

I’ve got 2 choices:
1. Remove some insulation, notch the joists for the cables and fix loft boards straight to the joists.
2. Increase the height of the loft floor by fixing some 4x2 on top of the 6x2, effectively making 10x2, If I do this I can notch out the 4x2 for the cables before screwing them down on to the 6x2.

My concerns with option one is that there will be insufficient space to dissipate the heat from the down lights in the ceiling after boarding over them as well as removing some insulation.

I’m only looking to board about 1.6m outwards from access door that was the original exterior wall as there is only a crawl space beyond that.

My plan was to cut 3m lengths of 4x2 in half to give me 1.5m 4x2s, screw these to the 6x2 and then use 320mm x1220mm x 18mm T&G loft boards. 5 of these come to 1.6m, I wasn’t going to worry about the 100mm overhang not being supported.

Any reason why I shouldn’t do this? I looked at loft legs but they’ll raise the floor too much, is the added weight of the 4x2 going to bee too much?

Thanks in advance
Nick

 

[blup]

What's the existing span of the joists?

Blup

 

[Dirtbike123]

About 3m, so I’m only looking to raise the height for about half the span as this is what will be boarded, it’ll be used for storage only

 

[blup]

Notching joists can seriously weaken them, and there would be no space to protect the downlighters from overheating.

Downlighter fire guards are available but it would be best to check with the manufacturer of your current lighting as to what would be suitable.

These guards can apparently be covered with insulation and boarded over but height wise may be too big for your requirements.

https://www.screwfix.com/p/halolite...mm/97932#product_additional_details_container

Blup

 

[Dirtbike123]

Ok, with that in mind I think I’ll go with option 2 and lay some 4x2 on top of the 6x2 joists and then board over that.

This should allow me to keep the existing insulation and give quite a bit of headroom for the back of the downlights, I’m going to swap the bulbs to LEDs so heat will be virtually non-existant.

As the 4x2 aren’t being used structurally, they’re basically just spacers, I was going to use non graded timber, I don’t think this is an issue as the original 6x2s are graded.

 

[foxhole]

Have similar at side of my property but built with storage in mind, have 125mm of celutex and ply over the top with wiring clipped to side of timbers. You could replace the insulation with rigid which requires less depth and if moving the wiring is not at option then just add 1” baton cut around any wiring to give clearance for boarding over .