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Old March 22nd 06, 11:33 AM posted to uk.d-i-y
Dave Page
 
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Default Raising Roof Joists for Loft Flooring

I am planning on insulating my loft to the recommended 270mm, and would
also like to lay floorboards above the insulation so I can keep using
the loft for storage. The gap between the ceiling and the top of the
existing joists is 70mm, so there's 200mm to go.

I'm intending on adding two strips of 40 x 100 on top of the existing
joists, screwing them down, and laying the insulation between them and
boards on top. It seems like a fairly simple job.

There's one bit of information I'm missing; what sort of timber would be
appropriate for this job?

Dave

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Old March 22nd 06, 11:52 AM posted to uk.d-i-y
Lobster
 
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Default Raising Roof Joists for Loft Flooring

Dave Page wrote:
I am planning on insulating my loft to the recommended 270mm, and would
also like to lay floorboards above the insulation so I can keep using
the loft for storage. The gap between the ceiling and the top of the
existing joists is 70mm, so there's 200mm to go.

I'm intending on adding two strips of 40 x 100 on top of the existing
joists, screwing them down, and laying the insulation between them and
boards on top. It seems like a fairly simple job.


When topping up old insulation (Rockwool) it's normal and more effective
to lay the second layer perpendicular to the first. So you'd be better
off fitting the new joists perpendicular to the originals I'd have
thought. However, your original ceiling joists are not very meaty, so
depending on the span, you may have a problem there, if you are going to
pile lots of new joists, floorboards and storage items up there.

There's one bit of information I'm missing; what sort of timber would be
appropriate for this job?


Just bog standard timber joists from the timber yard - haven't a clue
what species it is!

David
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Old March 22nd 06, 12:17 PM posted to uk.d-i-y
Dave Page
 
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Default Raising Roof Joists for Loft Flooring

Lobster wrote:

When topping up old insulation (Rockwool) it's normal and more
effective to lay the second layer perpendicular to the first.


I was intending to replace the existing insulation - it's only about an
inch thick, dead old (over 10 years), and patchily installed. Plus
insulation seems to come (from Wickes at least, who are selling rolls ad
near-half-price until this weekend) in 170mm and 100mm depths.

So you'd be better off fitting the new joists perpendicular to the
originals I'd have thought. However, your original ceiling joists
are not very meaty, so depending on the span, you may have a problem
there, if you are going to pile lots of new joists, floorboards and
storage items up there.


The joists are 14" / 355mm apart, so there are plenty of them (this is
particularly annoying since insulation roll seems to come in 400mm
widths). The thought of laying new joists crosswise is interesting, not
least because it would save me a few screws.

As it was, I'm not planning on putting too much weight up there, and was
considering only raising every other joist to save on timber. On the
other hand, the loft hatch is only 750mm wide, so if I want the boards
to be supported by three joists, I'll need to space the joists at
roughly 350mm anyway

There's one bit of information I'm missing; what sort of timber
would be appropriate for this job?


Just bog standard timber joists from the timber yard - haven't a clue
what species it is!


That sounds pretty useful. Wickes have some 40 x 100mm pre-cut 2.4m
lengths, I'll ask someone at the store whether it's suitable for my
purposes if it works out cheaper than a timber merchant.

Dave
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Old March 22nd 06, 12:32 PM posted to uk.d-i-y
The Natural Philosopher
 
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Default Raising Roof Joists for Loft Flooring

Lobster wrote:

When topping up old insulation (Rockwool) it's normal and more effective
to lay the second layer perpendicular to the first.


I think you mean 'orthogonal'

Perpendicular is walls... ;-)
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Old March 22nd 06, 12:52 PM posted to uk.d-i-y
Ian Stirling
 
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Default Raising Roof Joists for Loft Flooring

The Natural Philosopher wrote:
Lobster wrote:

When topping up old insulation (Rockwool) it's normal and more effective
to lay the second layer perpendicular to the first.


I think you mean 'orthogonal'

Perpendicular is walls... ;-)


Umm, no.
Perpendicular can also mean simply "a straight line at right angles to
another line".



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Old March 22nd 06, 01:32 PM posted to uk.d-i-y
The Natural Philosopher
 
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Default Raising Roof Joists for Loft Flooring

Ian Stirling wrote:
The Natural Philosopher wrote:
Lobster wrote:

When topping up old insulation (Rockwool) it's normal and more effective
to lay the second layer perpendicular to the first.

I think you mean 'orthogonal'

Perpendicular is walls... ;-)


Umm, no.
Perpendicular can also mean simply "a straight line at right angles to
another line".


....that is laying horizontal.

Orthogonal is better. Less implications of verticality.,
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Old March 22nd 06, 02:04 PM posted to uk.d-i-y
Dave Page
 
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Default Raising Roof Joists for Loft Flooring

The Natural Philosopher wrote:
Lobster wrote:


When topping up old insulation (Rockwool) it's normal and more
effective to lay the second layer perpendicular to the first.


I think you mean 'orthogonal'


Perpendicular is walls... ;-)


I understood what Lobster meant, and feel that "perpendicular" was quite
appropriate. After all, laying insulation foam vertically wouldn't make
sense.

Dave
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Old March 22nd 06, 02:15 PM posted to uk.d-i-y
Lobster
 
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Default Raising Roof Joists for Loft Flooring

Dave Page wrote:
Lobster wrote:

When topping up old insulation (Rockwool) it's normal and more
effective to lay the second layer perpendicular to the first.


I was intending to replace the existing insulation - it's only about an
inch thick, dead old (over 10 years), and patchily installed. Plus
insulation seems to come (from Wickes at least, who are selling rolls ad
near-half-price until this weekend) in 170mm and 100mm depths.


I wouldn't bother lifting the old stuff - 'orrible job, and it won't do
any harm being added to by what you're going to lay on top. I've used
the Wickes stuff; it's still intended to be laid perpendicularly (or
orthogonally - FFS!) even if you're starting from scratch (I think their
instruction sheet says so).

There's one bit of information I'm missing; what sort of timber would
be appropriate for this job?


Just bog standard timber joists from the timber yard - haven't a clue
what species it is!


That sounds pretty useful. Wickes have some 40 x 100mm pre-cut 2.4m
lengths, I'll ask someone at the store whether it's suitable for my
purposes if it works out cheaper than a timber merchant.


That's just the job, their 'kiln-dried', unfinished stuff is what you
want, with the purple sticker! Look down its length to check it's
straight before you put it on your trolley; especially if they haven't
got much stock in, a lot of it can be banana-shaped. Personally, I find
Wickes cheaper than timber yards as they won't give me decent trade prices.

Still not too happy about your weight issue though, but I could be wrong
- hopefully someone with more knowledge than me will comment?

David
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Old March 22nd 06, 02:24 PM posted to uk.d-i-y
John Cartmell
 
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Default Raising Roof Joists for Loft Flooring

In article ,
Dave Page wrote:
The Natural Philosopher wrote:
Lobster wrote:


When topping up old insulation (Rockwool) it's normal and more
effective to lay the second layer perpendicular to the first.


I think you mean 'orthogonal'


Perpendicular is walls... ;-)


I understood what Lobster meant, and feel that "perpendicular" was quite
appropriate. After all, laying insulation foam vertically wouldn't make
sense.


'Perpendicular' without the sense of vertical makes no sense at all. What
would it be hanging (-pend-) from?

--
John Cartmell john@ followed by finnybank.com 0845 006 8822
Qercus magazine FAX +44 (0)8700-519-527 www.finnybank.com
Qercus - the best guide to RISC OS computing

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Old March 22nd 06, 02:46 PM posted to uk.d-i-y
Lobster
 
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Default Raising Roof Joists for Loft Flooring

Dave Page wrote:
The Natural Philosopher wrote:

Lobster wrote:



When topping up old insulation (Rockwool) it's normal and more
effective to lay the second layer perpendicular to the first.



I think you mean 'orthogonal'



Perpendicular is walls... ;-)



I understood what Lobster meant, and feel that "perpendicular" was quite
appropriate.


Ah, but would you have understood if I'd said "orthogonal"? :-)

David


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