loft floor

[Damo1176]

Can I just ask, people talk of simply adding timber on top of joists. I have 3x2 joists in my loft and need to raise one half to cope with 200mm insulation before I board. My concern is if I simply add timber to raise the boards I will add too much weight to the original joists. Anyone got any sugestions how I go about raising them safely?
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lynda, moderator

please note forum rule 20

 

[markie]

You will be ok once you lay the floor down it's spreads the load

I work for a loft conversion company and i walk on the rafters and i'm 18 stone ( not all fat )
So a bit of timber on the rafters won't do nothing,

Any questions just post and i will answer if i can

 

[Damo1176]

If my joists are 3x2 and I need to get 200mm of loft insulation in I need to raise the joists by another 4" approx. what is the easiest way to build up the joists safely without adding too much weight

 

[markie]

Why do you need to raise the joists 4", if you are putting in normal loft insulation,
the 200mm insulation will compress down,
you could put 3" by 2" down, on top of the joists, but put them down opposite to what your joists are,
ie if your joists span from the back of the house to the front place the 3 by 2 from gable to gable so 1 bit of timber lies across a number of joist
so when you look down it looks like squares.
doing it that way saves you notching out your joists for the likes of eletric cables etc. ps hope u understand what i mean

 

[JohnD]

there was a very good post by masona on this very subject, included a better solution to getting the load onto the supporting walls. Have a browse with the Search option.

I previously used the counter-timbering method, which as markie says spreads the load and gives rigidity when screwed together, as well as space for cables and insulation, but my loft isn't living space or used for substantial storage, and like most people I didn't bother with building control just to store the Christmas tree, and change the ballcock without falling through the ceiling.



edited to say, I think this was the one, but have a look yourself, I remember there were several and this could save re-inventing the wheel. //www.diynot.com/forums/viewtopic.php?t=37387&start=0

 

[Damo1176]

I was informed that if you squash 200mm insulation down ie to fit in with 3x2 joists you will lose some of its insulation properties and put undue stress on the plasterboard ceiling below or so I was told,

 

[JohnD]

I was informed that if you squash 200mm insulation down ie to fit in with 3x2 joists you will lose some of its insulation properties and put undue stress on the plasterboard ceiling below or so I was told,

That's true. If you only have a 3" height of insulation then you only have 75mm of insulation. I think you need to add depth to the timbers before flooring, in one of the ways described above.

If you counter-timber like Markie and I did, you can snip half-way through the insulation with a big pair of scissors where it meets the upper timber, and you can fluff it up so it isn't squashed.

 

[Damo1176]

Strength wise do yo think I am safe to add 4x2 timber twice on top of the current 3x2 providing I cross them at 90 degrees as suggested earlier?? IN oder to fit the 270mm of insulation required this seems to be the only way if I want any boards down

 

[markie]

Yes.