Attic over battening/flooring

Darando

Going to floor an area of the attic. Joists are all irregular heights and spacing plus cables over a fair few of them. Was going to cross batten them in opposite direction at regular intervals and then use attic boards.

Question is what size timber (treated??)? 3x2 on edge or flat (75x44) or 2x2 (50x44) or something else? Ceilings are new with insulated board so don’t think I need any more insulation, plus 100mm of mineral fibre in between joists.

Calahonda52

You should have the equivalent of about 450mm of rockwool so I doubt if the insulated board is enough.

If adding more insulation you will need to sleep the power cables

What I use is 2 by 2 along line of existing rafters, and pre-drill them to take 4" screws and just build it up.
In one case I had 8 layers to get over sewer pipe
When u screw down the flooring it all gets stable

Stigura

I floored my attic, once. Used attic boards. Must have got about five of them screwed down before I noticed the writing on them: This Side Down

Never quite lived that one down!

cheif kaiser

Darando wrote: »

Going to floor an area of the attic. Joists are all irregular heights and spacing plus cables over a fair few of them. Was going to cross batten them in opposite direction at regular intervals and then use attic boards.

Question is what size timber (treated??)? 3x2 on edge or flat (75x44) or 2x2 (50x44) or something else? Ceilings are new with insulated board so don’t think I need any more insulation, plus 100mm of mineral fibre in between joists.

Did mine exactly like that but just used 2x2 timber. Turned out great and really sturdy.

Dr_Colossus

cheif kaiser wrote: »

Did mine exactly like that but just used 2x2 timber. Turned out great and really sturdy.

Tidy job, looks good, what size sheets did you manage to get up the hatch?

antiskeptic

I decked recently using stilts. Rather than buy those expensive plastic ones, I just used 16" lengths of 4x2 and screwed them into the joists from the side (screws angled downwards). Bit of care an attention to keep them level, then decked thereupon.

This allowed for a foot of insulation over the between joist insulation. And I was able to carry the heavy power cable (shower) over the insulation. I didn't bother with lighting cable, everything be low power LED.

GreeBo

antiskeptic wrote: »

I decked recently using stilts. Rather than buy those expensive plastic ones, I just used 16" lengths of 4x2 and screwed them into the joists from the side (screws angled downwards). Bit of care an attention to keep them level, then decked thereupon.

This allowed for a foot of insulation over the between joist insulation. And I was able to carry the heavy power cable (shower) over the insulation. I didn't bother with lighting cable, everything be low power LED.

4 or 6 legs per board and what length/width boards?

antiskeptic

GreeBo wrote: »

4 or 6 legs per board and what length/width boards?

The boards were 8'x2' OSB t&g. I was laying length perpendicular to the joist direction.

Supported either edge in the 2 ft direction, at every joist over the 8 ft direction. Joists about 400mm apart.

Up Donegal

Calahonda52 wrote: »

You should have the equivalent of about 450mm of rockwool so I doubt if the insulated board is enough.

If adding more insulation you will need to sleep the power cables

What I use is 2 by 2 along line of existing rafters, and pre-drill them to take 4" screws and just build it up.
In one case I had 8 layers to get over sewer pipe
When u screw down the flooring it all gets stable

Excuse my ignorance but what do you mean by 'to sleep the power cables'?

cheif kaiser

Dr_Colossus wrote: »

Tidy job, looks good, what size sheets did you manage to get up the hatch?

To be honest with you, I can't actually recall but do remember that it was somewhat of a struggle with bending and twisting to get them in.