OSB for loft boarding
The Night Tripper
I'm planning to board up the loft properly this winter - putting down 4x2s
at right-angles to the current joists and filling in between with a new
layer of insulation (Celotex/Kingspan or the normal roll insulation stuff),
then boarding over the result.
I'm unimpressed with the T&G chipboard panels the sheds sell for this
purpose and was thinking of using OSB, probably cut into eg. 4ft x 2ft
panels for easy of fitting.
Any thoughts on the right thickness of OSB to use? 18mm seems a whisker OTT,
but I don't think I would trust 11mm. I guess I'm thinking of around 400mm
'joist' spacing.
Thanks
J^n
Stuart Noble
> Hi All
> I'm planning to board up the loft properly this winter - putting down 4x2s
> at right-angles to the current joists and filling in between with a new
> layer of insulation (Celotex/Kingspan or the normal roll insulation stuff),
> then boarding over the result.
>
> I'm unimpressed with the T&G chipboard panels the sheds sell for this
> purpose and was thinking of using OSB, probably cut into eg. 4ft x 2ft
> panels for easy of fitting.
What don't you like about the chipboard panels? They're designed for the
job.
PeterC
Been looking at this recently and same feeling re. T&G chipboard - also
want to be able to lift individual sheets for access to various things.
Wickes' chipboard and OSB seems good, not just cheap water-soluble stuff.
For OSB, have a look at
http://www.osb-info.org/rightgrade.html
Wickes stock:
OSB/3
Load-bearing applications in humid conditions
Plywood - exterior/WBP is an option, although expensive. 18mm would do, be
heavy and expensive. 12mm might be too thin, but I've tried an offcut of
12mm across 3 joists; it does flex a bit but not badly and in wider pieces
and with a few screws in might be OK.
In another thread, whitewood plain (non-T&G) floorboards were mentioned
(from Jewson, IIRC). That would be an easy, modular, way od doing the job.
The wood would have to be treated and normalised (but even OSB needs
normalising).
--
Peter.
The head of a pin will hold more angels if
it's been flattened with an angel-grinder.
NT
google sagulator, it'll tell you how much flex you'll get with the
various flooring options.
I prefer non-T&G chip for easy access.
NT
geraldthehamster
> I'm planning to board up the loft properly this winter - putting down 4x2s
> at right-angles to the current joists and filling in between with a new
> layer of insulation (Celotex/Kingspan or the normal roll insulation stuff),
> then boarding over the result.
For what it's worth, if you can get to the ends of the existing joists
(4x2?) where they sit on the wall plate, and glue and screw your new
4x2s on top of them for their full length, you will make a much
stronger floor than by just laying 4x2 across the joists. Effectively
you would be creating new 8x2 joists, which is almost up to current
Building Regs for a proper floor.
My bungalow is a good illustration of this principle. The chap who
built it used 7x2 joists for half the first floor, and 4x2 for the
other half (don't ask me why; much of the material was scavenged so
it's probably what he could get hold of). When he had a family he made
some rooms up there. To have a level floor he laid 3x2 over the 4x2 on
that side of the house. So - one half of the floor was on 7x2, and the
other on what you propose. The 7x2 side was rock solid, and the 4x2 +
crosswise 3x2 tended to move up and down, which not only felt unstable
but produced cracks between the plasterboards in the ceiling below
(I've since removed the overlayed 3x2, and installed new 7x2 between
the original 4x2).
You're not converting your loft to habitable space, but it's worth
considering making the floor as strong as you can, so you have the
option of storing heavy stuff up there without worrying about the
loading.
Cheers
Richard
Dave Liquorice
> What don't you like about the chipboard panels? They're designed for the
> job.
The price? At least that is the impression I have compared to buying
similar chipboard in 8x4 sheets. I guess they are fine if their
dimensions also happen to coincide with the joist spacing. Personally
I'd rather buy enough sheet and cut to fit the spacing I have rather
than faff about trying to fit silly little panels to the spacing and
still ending up cutting or fitting noggins etc.
--
Cheers
Dave.
auct...@sheldononline.co.uk
Saw this when I was in BnQ the other day - don't know if it's any
good, and I've not worked out the relative costs, but would be an
easier solution possibly:
http://www.diy.com/diy/jsp/bq/nav.jsp?action=detail&fh_secondid=10647753
A
Stuart Noble
Depends whether you regard t&g as beneficial. If the joists aren't
level, it at least makes the joints flat. The 8x2 t&g sheets are handy
if you have the space to handle them in the loft.
I always end up laying the small panels across the joists anyway, but
I've been lucky with the spacings, so the wastage wasn't too serious.
fred
Night Tripper <jkn...@nicorp.co.uk> writes
boarding over without the additional cross joists? Celotex is pretty
good in compression and as long as it's not pianos that you're storing
up there, then it could be the way to go. Avoid having Celotex sheet
joins on the joists, the edges would be more likely to crumble.
11/12mm would prob be a match for this sort of light, load spreading
design.
--
fred
BBC3, ITV2/3/4, channels going to the DOGs
The Night Tripper
>
> What don't you like about the chipboard panels? They're designed for the
> job.
>
acceptability and with low cost as the maind driver.
The ones I have encountered are very crumbly near the T&G edges and do not
take screws well. They are also on the thin side and the sag they
demonstrate when standing on do not give me much confidence. To me they are
an example of something designed by the 'sheds' to appeal to those with
little knowledge of what else might be available but for whom convenience of
purchasing and packaging are major criteria
(I don't mean you by this, Stuart!)
J^n
The Night Tripper
>
> For what it's worth, if you can get to the ends of the existing joists
> (4x2?) where they sit on the wall plate, and glue and screw your new
> 4x2s on top of them for their full length, you will make a much
> stronger floor than by just laying 4x2 across the joists. Effectively
> you would be creating new 8x2 joists, which is almost up to current
> Building Regs for a proper floor.
I would like to do this, and can get to the ends of the existing joists -
but I can't get new timber the same length as the joists into the loft! I
will have to cut them down into sections approx 3m long, which presumably
would spoil most of the effect you mention.
I suppose one could find a way of re-joining the timber once up there -
ideas?
Cheers
J^n
The Night Tripper
Thanks for the links etc.
> In another thread, whitewood plain (non-T&G) floorboards were mentioned
> (from Jewson, IIRC). That would be an easy, modular, way od doing the job.
> The wood would have to be treated and normalised (but even OSB needs
> normalising).
Yes, I will price up floorboarding to check the relative costs. I've a
feeling 4ft by 2ft panels will be easier to lay though.
by 'normalising' I assume you mean leaving in the appropriate atmosphere for
a period of time?
Thanks
J^n
Tim W
wibbled on Thursday 08 October 2009 22:55
> Hi Stuart
>>
>> What don't you like about the chipboard panels? They're designed for the
>> job.
>>
> IMO they are designed for doing the job to the very lowest level of
> acceptability and with low cost as the maind driver.
I'll add that all the ones I've been ripping up (later to bin) are filling
my ceiling voids with not insignificant amounts of sawdust aka mouse fodder
and fire tinder. I hate them. Brand new ones are OK (I bought one pack from
Wickes just to give myself some short term boarding in the roof corners),
but IME they really don't age well... Planks of wood or ply are way better.
--
Tim Watts
This space intentionally left blank...
Stuart Noble
Well, that's me alright! It's a loft, not a living room :-)
They've been absolutely fine in my loft for the last 15 years or so, and
I've had sawbenches and all sorts of heavy stuff up there. I've never
seen the need to screw them to the joists at all. As long as the edges
are fixed, how are they ever going to move?
PeterC
> Hi Peter
>
> Thanks for the links etc.
>
>> In another thread, whitewood plain (non-T&G) floorboards were mentioned
>> (from Jewson, IIRC). That would be an easy, modular, way od doing the job.
>> The wood would have to be treated and normalised (but even OSB needs
>> normalising).
>
> Yes, I will price up floorboarding to check the relative costs. I've a
> feeling 4ft by 2ft panels will be easier to lay though.
I'd like to know the results, please. I did look at Jewsons' site but
couldn't see any and I'm too far from doing the job to ring atm.
I'd prefer panels but can't get them up there on my own (8x4 will just
about go but need angling and steering carefully), so floorboards, in spite
of the need to treat them, would be manageable.
>
> by 'normalising' I assume you mean leaving in the appropriate atmosphere for
> a period of time?
>
> Thanks
> J^n
Yes. I was surprised tha OSB needed this as it has a lot of synthetic
content. Important for floorboards as there a many gaps (especially T&G).
In a loft, of course, the conditions are far more variable than in a
bedroom, so what is 'normal'?
NT
> On Thu, 08 Oct 2009 23:01:32 +0100, The Night Tripper wrote:
> > Hi Peter
>
> > Thanks for the links etc.
>
> >> In another thread, whitewood plain (non-T&G) floorboards were mentioned
> >> (from Jewson, IIRC). That would be an easy, modular, way od doing the job.
> >> The wood would have to be treated and normalised (but even OSB needs
> >> normalising).
>
> > Yes, I will price up floorboarding to check the relative costs. I've a
> > feeling 4ft by 2ft panels will be easier to lay though.
>
> I'd like to know the results, please. I did look at Jewsons' site but
> couldn't see any and I'm too far from doing the job to ring atm.
>
> I'd prefer panels but can't get them up there on my own (8x4 will just
> about go but need angling and steering carefully), so floorboards, in spite
> of the need to treat them, would be manageable.
why would you need to treat them?
NT
PeterC
Untreated wood in a loft? I had that in a brick shed (similar conditions)
and got woodworm. OSB, WBP and chipboard aren't so palatable to the little
blighters.
The Night Tripper
>>
> Have you considered laying Celotex directly on the old joists and
> boarding over without the additional cross joists? Celotex is pretty
> good in compression and as long as it's not pianos that you're storing
> up there, then it could be the way to go. Avoid having Celotex sheet
> joins on the joists, the edges would be more likely to crumble.
I have thought about this, but I don't like the idea of doing it with
*small* (4ft x 2ft) panels. It feels like it be a lot of work faffing around
with lining the panels properly over the joists, with the Celotex in the
way. I also have the picture of all the panels giving way to different
degrees, with the whole thing ending up looking like badly laid paving
slabs, if you see what I mean... (OK, i know, it's only a loft...)
I'm also considering doing only (say) half of the loft in one guy, but
buying all the materials. if I cut down celotex to suit then I can stack it
vertically for now.
But I'm happy to be convinced that this is a better way to do it than any
I've come up with ...
The Night Tripper
>> Yes, I will price up floorboarding to check the relative costs. I've a
>> feeling 4ft by 2ft panels will be easier to lay though.
>
> I'd like to know the results, please. I did look at Jewsons' site but
> couldn't see any and I'm too far from doing the job to ring atm.
>
A few things I've found out:
eBay do reclaimed floorboards (see a thread from a month or so ago) but they
tend to be of 'architectural interest' and be around £20/sqm. You could
probably find some for £15 per sqm, not sure about delivery.
Wickes PTG softwood flooring - packs of 5 (18mm x 121mm x 3m) is £22.40, ~
£13.25 per sq. meter.
11mm OSB (2440 x 607 x 11mm) is £8.98, £6.07 per sqm
18mm OSB3 T&G Roof Deck (2440 x 1200 x 18mm) is £19.95, £6.81 per sqm. T&G
on the long sides.
Loft Panels (ie. what I don't like)
Pack of 3 (1220 x 320 x 18mm), £4.87, £4.17 per SQM.
FWIW I played with the sagulator a bit. Since the gradings for particle
board are not ones I'm familiar with, nor know the UK equivalents of, this
is all a bit handwaving. And I put fairly arbitary figures in for shelf load
and span etc. However, for purposes of comparison only:
(all 18mm thickness)
particle board sag: min 0.9mm, max 1.5mm
MDF: similar to particle board
OSB: min 0.30mm, max 0.55mm
Various types of pine: < 0.3mm
The OSB is still looking good to me -I'm going to try to cost some 15mm OSB
panels.
HTH
J^n
PeterC
Intersting figures, thank you.
I'd be very interested in 15mm OSB as I've seen only 11/12mm and 18mm.
Trying an off-cut of 12mm WBP indicated significant flexure; this was
across 2 joists and only about 60cm wide. Longer, wider and screwed down
would help stiffen it a bit.
fred
Night Tripper <jkn...@nicorp.co.uk> writes
It helps if you have some Celotex/Kingspan lying around as you can see
how tough it is in compression.
As a test, I just took a spare small piece of 'tex and placed it over a
couple of 18mm wide battens before adding a small board on top and
jumping up and down on it. It did creak and deform by about 0.5mm at the
battens so it was at the limit but that was 80kg+ over only 50cm2 of
narrow contact on the battens. Scale that up to 50mm joists at say 500mm
centres and the test was equiv to 3200kg/m2 so it suggests that a few
100Kg/m2 would be well within safe limits.
As to alignment, if you lay the 'tex and mark the joist positions on the
top foil surface with a marker pen then it is relatively easy to keep
track of their positions. If you were then to align the OSB with the
edges within 25mm of the joist position then I would say that was safe
enough. I wouldn't even screw the boards down (unless it proved
necessary) but would float it and tape the seams with good quality duct
tape. Just keep the 'tex joints away from the joists.
How does that sound? It seems a lot less work that cross joisting.
The Night Tripper
>
> It helps if you have some Celotex/Kingspan lying around as you can see
> how tough it is in compression.
>
> As a test, I just took a spare small piece of 'tex and placed it over a
> couple of 18mm wide battens before adding a small board on top and
> jumping up and down on it. It did creak and deform by about 0.5mm at the
> battens so it was at the limit but that was 80kg+ over only 50cm2 of
> narrow contact on the battens. Scale that up to 50mm joists at say 500mm
> centres and the test was equiv to 3200kg/m2 so it suggests that a few
> 100Kg/m2 would be well within safe limits.
>
> As to alignment, if you lay the 'tex and mark the joist positions on the
> top foil surface with a marker pen then it is relatively easy to keep
> track of their positions. If you were then to align the OSB with the
> edges within 25mm of the joist position then I would say that was safe
> enough. I wouldn't even screw the boards down (unless it proved
> necessary) but would float it and tape the seams with good quality duct
> tape. Just keep the 'tex joints away from the joists.
>
> How does that sound? It seems a lot less work that cross joisting.
Thanks for this; I'm aware that my reservations are in part due to lack of
real experience with Celotex. I've tried to press my thumb into a sheet in
Wickes; that's about all ;-/
What thickness of Celotex are we talking about here anyway?
That all sounds reasonable, and as you say much less work than cross
joisting. I'm still not too sure about the relative staggering of the
Celotex and OSB panels though - especially if they're both of a similar size
to go through the loft hatch. I will do a few layout doodles and see what I
can come up with. I would quite like to be persuaded that this is the way to
go ;-).
Cheers
J^n
fred
<jkn...@nicorp.co.uk> writes
>
>Thanks for this; I'm aware that my reservations are in part due to lack of
>real experience with Celotex. I've tried to press my thumb into a sheet in
>Wickes; that's about all ;-/
>
>What thickness of Celotex are we talking about here anyway?
>
it would be the same result for thicker stuff. PIR foams are close to
twice as effective as fibreglass so a 50mm sheet plus say 4" of
fibreglass that you may already have between your existing joists would
be about right.
>That all sounds reasonable, and as you say much less work than cross
>joisting. I'm still not too sure about the relative staggering of the
>Celotex and OSB panels though - especially if they're both of a similar size
>to go through the loft hatch. I will do a few layout doodles and see what I
>can come up with. I would quite like to be persuaded that this is the way to
>go ;-).
>
Perhaps a bit more difficult with the short sheets but maybe a staggered
arrangement will work somehow, get sketchin :-!
Forgot to say, there are places you can buy Celotex and Kingspan in
light seconds grades at much reduced prices, google for Celotex/Kingspan
seconds. Here's a couple from my bookmarks, don't know if they're any
good:
http://www.secondsandco.co.uk/
http://www.seconds.co.uk/
The Night Tripper
>>
>>What thickness of Celotex are we talking about here anyway?
>>
> The sample I used for the crush test was an offcut of 25mm but I think
> it would be the same result for thicker stuff. PIR foams are close to
> twice as effective as fibreglass so a 50mm sheet plus say 4" of
> fibreglass that you may already have between your existing joists would
> be about right.
Hmm. I had 50 or 100mm in my head, that's maybe one reason for my concerns.
I haven't done the relevant U-calculations, will have to get around to that.
If 50mm Celotex would do thermally (I have some decrepit fibreglass between
the joists at the moment and already have some new rolls up in the loft
ready to lay prior to anything else) then I'd be reasonably happy with this
construction.
>
> Forgot to say, there are places you can buy Celotex and Kingspan in
> light seconds grades at much reduced prices, google for Celotex/Kingspan
> seconds. Here's a couple from my bookmarks, don't know if they're any
> good:
> http://www.secondsandco.co.uk/
> http://www.seconds.co.uk/
Sure - I know about those, thanks. Secondsandco have a better website but
are based in Wales. Seconds seem to be closer to be (Tunbridge Wells - I'm
near Brighton) but i'll check both of them out.
Cheers
J^n