Boarding out loft solutions

[jayc89]

I'm looking to board out our loft, joists are approx 150mm deep at 400 centres. There's a couple of king post trusses up there so not much of a clear run. Right now there's around 200mm of rock wool insulation, but I plan to have 300mm blown cellulose installed next year. This means anything I do needs to be at least 150mm above the current joists. I've seen systems like LoftZone and LoftLegs which look useful, but quite expensive for the size of our loft, (approx 11m x 7m - but I'd likely leave a 1m perimeter to allow for ventilation - probably in-line with a couple of chimney stacks come through the roof void)

 

I looked at using something twist strap or strong ties, but 1) getting 150mm battens up there would be a PITA and 2) be expensive.

 

Twist straps and timber legs looks to be approx. half the price of any bought-in "solution." Are there any other, cheaper, alternatives?

[Radian]

I'm not sure what you mean by 150mm battens - do you mean running joists perpendicular to the rafters so support the floor? This would indeed be expensive not to mention heavy. You will need to add at least 50mm for an air-gap over the insulation or it will turn into a mouldy mess without decent airflow over it. Now you're flying your floor at least 200mm up!

 

I'm afraid to say it's not as simple as you might think.

 

Do you really need this space? If so, it might be more practical to move the insulation up to the rafters and make this a semi-warm store. Or at least for a specific zone in the loft. You're still going to need to insulate for the whole house so at least 150mm of rigid insulation to make up for 300mm of cellulose in this area. All the usual ventilation issues need addressing - like a 50mm air gap between insulation and roof membrane and vapor barriers. The advantage would be having a safer environment for the items you're storing, and improving the house's ability to reject heat in the summer.

[S2D2]

I've used loft legs, the XL version and they worked very well. Shouldn't be too expensive if you buy by the box rather than individually. Remember they can be spaced at 600mm along the joists, but yes the 400mm joist spacing will increase the number required in the other direction.

 

Use the expensive screws which don't require pilot holes and self countersink, they pay for themselves in about five minutes and make the job very quick indeed.