Loft stilts

[Longshanks]

Hi

Have put down 170mm of insulation and about to lay another 100mm at right angles etc (total equates to about 300mm with existing,rotting, insulation.

I need storage so will be using loft stilts. Looking at info it's advised to fit these before laying second level of insulation etc.

I won't be boarding the whole loft but not sure how you can attach stilts 600mm apart when loft roll will be approx 1400mm.

Many thanks.

 

[Longshanks]

Hola amigos

Dire unas pocas palabras. Siempre hay algunas problemas acqui.

No puedo entenderlo todo en cuanto al suelo del desvan no??

Bueno, me allegro que haya ayudarme bastante bien.

Tengo dolor la cabeza muy grande ahora.

Adio pero no haya con dios

 

[Longshanks]

Las ultimas palabras:

Adios pero no vayan con dios.[/i]

 

[Longshanks]

Hi again

Forgive the use of pure Castilian but thought that might get more response than the original Anglo Saxon (with just a touch of Viking).

I've now added photos and you will see how the 170mm layer is sort of puffed up, well above the level of the joists, as laid on top of original stuff. If I screw in loft stilts and then lay second layer at right angles (100mm or 170mm) then the insulation would be above the height of the top of the stilts? This is as opposed to the stilts poking through the top of the insulation…

My question boils down to this:

Would I be better off leaving the insulation as it is and just fit the loft stilts and board on top?

Simples innit.

Thanks you
View media item 92579 View media item 92578

 

[big-all]

i dont like loft stilts they do not spread the load
you would need stilts at around 280 centre to give the same support as 2 parallel timbers at 400 centres
go for 4x2 timber at 90%

 

[Longshanks]

Thanks for response. However:

What about my point re virtue of adding second layer that might bring height above level of loft stilts?

Also not clear on terminology re 280 centre/400 centre etc.

Thanks

 

[big-all]

centres means distance apart from the centre off item to the centre off the next item

what size are your present timbers ??

another 100mm will save very little
iff the first 50mm saves say 75 % loss
the second 50 mm will again save around 75% but off 15% so 5
the next 50mm will again save 75% but now 1.5

now assuming you loose say 20% off your heating through the loft without insulation and you house is well insulated so your bills for heating are £400 a year so the losses through the roof have been reduced from £80 a year to around £2 on 170mm the next 50mm will save a further 50p a year then 12p
so a further 100mm would save a further 62p a year

now the actual amount will vary but you get the idea about diminishing returns

 

[Longshanks]

Thanks. Yes, can appreciate your logic. I wonder then, why the mantra is at least 250mm etc etc. What's all that about?

 

[big-all]

my exact percentages may be out by quite a bit
sometimes when savings are small its better to look in other areas for better returns
for example changing one normal 100w bulb for a 12w led bulb can save you 88w per hour at say 10 hrs a day average about 13p at 15p a unit
thats 90p a week or £48 a year even for 5 hrs its £24 a year and will pay for its self in around 3 months
http://www.toolstation.com/shop/p14618

 

[Longshanks]

Hi again

Just been back up the loft. Joists are 100mm high and 570mm apart. Is that what you were asking about

Insulation is approx 170mm as stated previously.

Diminishing returns made me recall concepts of marginal revenue and marginal costs from Economics at Uni

 

[big-all]

Hi again

Just been back up the loft. Joists are 100mm high and 570mm apart. Is that what you were asking about

Insulation is approx 170mm as stated previously.

Diminishing returns made me recall concepts of marginal revenue and marginal costs from Economics at Uni

i have my uses then

600 apart ouch
should have asked what the unsupported span was [wall to wall or supporting beam underneath]

 

[Longshanks]

Sorry, just spend 3 wonderful days (not) with the outlaws so only just got back home.

I won't pretend to understand why the 570mm gap between joists generated that negative response. I'm guessing that I'm not the only one with this spec. (1981 Wimpey house). I'll pop into loft tomorrow and report back on measurement requested. I think I'll have to use the stilts as have no alternative and need the space. However, I've noticed that all my existing loft boards are 400mm width and not the 320mm as available now. Can I still use these with stilts fitted at 400mm etc etc?

Thanks

 

[gregers]

600mm centers mean you probably have a trussed roof,rather then a cut n pitch roof which may well have 400mm centers.
typical newish houses im afraid,you start using the oft for storage then you may notice how much deflection there is.

 

[Longshanks]

Yes , definitely truss roof with all the familiar drawbacks. "Deflection" is obviously another technical term I'm not au fair with. That said have had the whole loft space boarded for about 15 years now so a bit late to worry I guess. I'm removing board to add extra insulation with view to using loft stilts as indicated. I don't intend to use stilts all over, just selectively. I have loads of board to use but notice that it's 400m width rather than 320mm. As this is not >600mm I thought it would be good to use them.

Ta

 

[big-all]

well my advice is not to use legs at 400 centres as this gives an unsupported span off 580mm [diagonal ]
so i definitely don't like 600 at 870mm and the point loading [unspread load]

i fear you quest to be highly insulated is at the risk off your platform giving way and your ceilings cracking or collapsing
i will now step away and let others reassure you but i wont good luck