Anyone used 'loft flooring legs' instead of cross battening

[roxburd]

digdilem: Damn good point, thanks.

 

[timmel]

They look like a good idea which on further study may be a bad idea.

Unsure how often these are supposed to go, but even at a short distance they will introduce point loading on the joists below. If those joists are typical ceiling joists and you're storing a lot of weight above, they'll bow out of shape and spoil the ceiling below.

Wooden battens will spread the weight evenly and if spanning is possible, strengthen the surface rather than weaken it.

I have to disagree I'm afraid... In theory they are point loads, but multiple point loads, which is not much different to cross battening, which also creates multiple point loads where the battens cross.

Cross battening will strengthen the joists in terms of stiffness but will still add additional weight, particularly if using 7 x 2's which are pretty weighty.

 

[Sludgeguts]

I did my loft a couple of years ago. I already had the recommended 100mm - which seemed, to me, to be more than adequate judging by the amount of frost I had on my roof compared to nearby houses.
However, as the new regs said 250mm is better, I figured it would be good to upgrade.
How to increase the depth of the joists though? I thought about using 6" timbers across the existing joists (adding extra strength as well) but thought the added weight wouldn't help - especially with the amount of clutter we have up there - so I made up my own I beams using 38x47mmx2400 treated timber and 2400x1200x9mm OSB.
I bought the OSB from B&Q as they were the only local place offering free cutting
I got 10 widths from each sheet of osb, cut a groove down the centre of each length of timber & glued them to the osb to form the I beams. I also glued 4 uprights to each side (and screwed through the osb) to increase rigidity. Cost me less than £50 to raise my loft floor.

 

[Garaged200]

Hi Gents,

I'm still on this. In fact was going to commence this weekend (lots of 'life' has been getting in the way since i started this thread )

Im still going with the cross battern idea with packer 'feet' to gain height.

Issue 1:

Now i'm looking to use 22mm x100mm (haven't asked if you can get x125mm yet). I dont intend on cross battening everywhere but will require around 53m to go into the attic. Now 53m @ 100x22mm (using wood density of 0.5x10-6) equates to 1.1kg/m and thats 58.3kg of wood before i even think of putting board down. My thoughts are i certainly weigh more than 58kg, however i'm not spread over the centre of the attic which is ~28m2, and that is 2kg/m2.

Is there a rule of thumb for load per m2?

Issue 2:

I aiming to lift the floor enough for my 170mm insulation. Using the above battern dims my intention was to allow 20mm to sit down in/on the existing insulation, then 4" tall plus 1" 'feet' gives me ~125mm and then i was hoping that compressing the final 1" wouldn't matter too much. (Thus compressing 170mm into 145mm gap). However reading through i few threads i'm now worried about not having an air gap?
(The attic in general doesn't seem to currently get damp and there are the usual B&Q T&G flaoting around up there that seem to be fine)

On a side note would anyone recommend putting floor foil under the boards prior to fitting? - Just to add the insulation.

Kind regards

PS: I'll be taking photos before, during after so will lokk for opinions - just dont fancy a "You shouldn't have done that" response.

 

[Garaged200]

Hi again.

Just thought i'd note something i found in the small print on the rear of a 'Focus DIY Insulate a Loft Guide'.

Its says:

- To build a storage platform you may need to increase joist depth to raise them over the top of the insulation layers. Fix treated timber (10x5cm) on top of existing joists; then add chipboard loft panels. Panels must have holes drilled in them to allow the passage of water vapour into the ventilated loft. Drill rows of 10mm holes in the loft boards at a minimum 100mm centres

I think the part i've highlighted in green may come in handy

Cheers

 

[big-all]

legs are bad news you increase the span by 40% as you have to measure the diagonals as that gives you the minimum span between supports
cross joists spread the load effectively over several timbers with no point loading