Advice on loft flooring

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Hi I'm looking into flooring my loft and looking for a bit of advice on how people with a bit more knowledge think I should go with it. I did some measurements and drew up a plan of what's there already. It's an old style house, built around 1969.

open-plan.png


The dark grey part is the hatch. The horizontal lines are the joists (correct me if I get the terminology wrong/mixed up) and the brown vertical lines are what I believe, from my research, to be binders. The middle binder was cut when I got someone to install a bigger hatch. The pink area on the right hasn't been floored at all, the yellow in the middle has been floored with regular wood planks, but directly on the joists and the insulation under is a bit squashed and the the blue area on the left has been floored over the binders with chipboard, but I don't think it's proper flooring chipboard and it's a bit flimsy to stand on anywhere other than the middle or sides where the binders are supporting it. The light grey areas are the eaves, which do go further than the area I have drawn.

Here are some photos taken from the hatch to get an idea of the different areas:

IMG_20221110_201626004.jpg
IMG_20221110_201905652.jpg
IMG_20221110_201718258.jpg

My original thoughts are to remove the flooring that is already there, floor the middle three coloured areas and then a little out into the eaves for storage. Of course I would tidy up the insulation properly under the new boards as I went.

I was looking at standard loft boards that are around 122x31cm. One thought I had was to utilise the binders similar to the way that has been done in the blue area above. Here's something I drew up to show this, obviously the part that covers the hatch would need to be shaped round it:

plan-across-binders.png


It turns out that those boards would sit nicely sized across the binders. If I did this I was considering working out some raised platforms in the eaves for storage rather than going full flooring since that area wouldn't need to be walked on anyway. A few questions about the flooring area though:

  1. Are binders acceptable supports for flooring?
  2. I assume that I would need at least one support in the middle of each board?
  3. I thought that I could maybe use loft legs/stilts as supports in the middle, but the smallest I can find raise the floor by about 20.5cm and the difference in height between the joists and binders is about 13cm.
    • Are there any smaller loft legs available?
    • Could I use wood cut to size rather than loft legs?
    • Could I extend the height of the binders to line up with the height of loft legs in the middle?
  4. If there's a solution for the above points there's still an issue with boards that don't cover joists for the extra support, such as the one 4th from the left or the one 7th from the left where it not only isn't above a joist, it also isn't above a middle binder since it was cut for the hatch installation. Would crossbeams such as these: https://www.loftzone.co.uk/loft-storefloor/ be useful for these bits?
  5. Instead of loft legs/crossbeams for the middle support could I just add some more beams of wood across the middle of the joists, effectively adding more binders?

The other option I was thinking of was rotating the loft boards 90 degrees from the idea above and installing them on the joists with loft legs, as seems to be the main suggestion I've read about. I started putting a drawing together to show how this would maybe work, though I didn't finish filling in the whole floor area, yet:

plan-across-joists.png


I read that staggering them is better. To me, however, this seems like a lot more work, cost and would leave quite a bit more waste. I would need to cut every board so that it didn't overhang from the joist leg supports, there would be lots of small cut offs I couldn't do much with and I'd need to invest in a lot more legs. If I did it this way I would probably just extend the flooring out into the eaves for the storage space too.

what are peoples thoughts about this? If I can get the first option to work then I think that might be the best option, but everything I'm reading seems to suggest that I should do it the second way.
 
I'm so confused! But if I were you, I'd lay some new joists across the "binders" to increase the space available for insulation - this should be your first priority - ceiling joists (75/100mm?) + binders (130mm) = 200mm - the bare minimum these days is 300mm (and possibly up to 450mm). If you use 89x38mm CLS on top (probably the cheapest structural timber around these days) you will be getting close, if you want more and have the headroom you can pack under the CLS. As you have suggested, the eaves area is best reserved for raised/shelf type storage with plenty of room for insulation below.

Personally I'm not a fan of those legs as I think they can introduce point loads onto the ceiling joists and cause cracking to the finish below as there is no load sharing.

I would also have a look at the cut binder and ensure it is adequately supported.

IMG_20221111_083228972.jpg
 
I'm so confused! But if I were you, I'd lay some new joists across the "binders" to increase the space available for insulation - this should be your first priority - ceiling joists (75/100mm?) + binders (130mm) = 200mm - the bare minimum these days is 300mm (and possibly up to 450mm). If you use 89x38mm CLS on top (probably the cheapest structural timber around these days) you will be getting close, if you want more and have the headroom you can pack under the CLS. As you have suggested, the eaves area is best reserved for raised/shelf type storage with plenty of room for insulation below.

Personally I'm not a fan of those legs as I think they can introduce point loads onto the ceiling joists and cause cracking to the finish below as there is no load sharing.

I would also have a look at the cut binder and ensure it is adequately supported.

View attachment 285259

Thanks, sorry for the confusion. Was trying to explain best I could.

I think the cut binder has enough support. You put the word binder in quotation marks, is there another name for it? That's the name I got from my research.

Would you line the new joists up with the same positions of the old ones or maybe line them up more to go along with the sizes of the new flooring? Then line the flooring up similar to my last image?
 
Position the joists to suit you within reason - it's a loft and only suitable for light storage and occasional access so it doesn't matter if your platform deflects (sags) a bit as long as nothing touches the ceilings. The less extra weight of joist and flooring up there the better. I just shoved a load of old internal doors in my eaves because it's literally just suitcases and Christmas decs stored there.

I highlighted binders because I'm not entirely sure if they are - the ones I've seen are very shallow and laid flat (their purpose is to bind the ceiling joists together so they share the load and don't twist). Yours look more like some kind of supporting beams - but I don't know what they're called!
 
Thanks for the advice.

Wondering if anyone else has any input?
 
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