How can you satisfactorily board part of a loft given the large
thickness of insulation now recommended? I know this question has
been asked before, and I have searched the group's archive, but none
of the suggestions has really been very practical. Most ideas have
been to raise the boarding above the insulation by effectively
increasing the height of the joists, but apart from the sheer effort
involved the extra weight must compromise the use of the loft for
Would it be possible (at a price) to use one of the foil-based
insulating products, in place of some or all of the existing
insulation, to achieve the necessary U-value but with a considerably
reduced total thickness?
What I did in our loft was to screw 2 lots of 2 x 2 to the existing wood
and then add another 4 inches of insulation.
In order to keep the additional weight down, so as to continue to use
the loft for storage, I laid light weight floor boards spaced with gaps
that you could not get your foot stuck in them. Just don't consider
using chip board, it is just too heavy and will compromise the strength
of the loft floor.
Works fine here.
The extra weight of the wood is trivial I would have thought.
I suppose you could always replace rockwool with 100mm celotex which is
supposed to be twice as effective. You might get your money back in 100
years or so.
This is not a good idea but if you insist then the best way would be
to increase depth of the ceiling joists AND increase the stiffness and
strenght at the same time. This can be achieved by careful gluing and
screwing of, say, 10 mm plywood to the side of the existing joists
using a decent structural UF or similar glue and screws or nails at,
say, 150mm centres up as high as you want the new floor - shall we
guess 300mm up? Then put your new 4 x 2" along side the top of the ply
and similarly glue and screw/ nail.
You will find you have now constructed an (almost) "I" beam and if it
has been done correctly will be nice and stiff . It is quite possible
that a calculation may reveal that you only need do this every other
set of CJs - but it may not - you would have to get a timber engineer
to do this for you.
One problem to overcome would be at the eaves where the top part of
the chord would not be complete resulting in an incomplete balancing
of the moment between tension and compression zones. I suspect but
dont know that this so close to the bearing would not be a problem but
you might have to suplement this by putting ply on the other side and
forming a box beam for say 1000mm from the wall.
I would then put on the lightest boading you can get away with and
load up the sides before the middle and only use it for light and
Dont forget the effects of duration of load on timber.
I'm sure that I once read somewhere that the best way is to move the
insulation layer to the slates/tiles with a vapour barrier - some of the
modern insulating materials should be good here - then board with
insulating boarding. You don't want any insulation at all in the new
floor, as this removes a source of heat for your new room and can lead to
problems with wiring etc. The floor can then use interlocked boarding to
spread the load.
I'm not saying that this is right or wrong, but it seems a sensible way
to do it.
We did both. There was existing insulation between the joists (expanded
mica) so we added to it then boarded. Then we put slabs of something between
the 'ceiling' members and clad over that.
Yes, the space is cold but that's fine because it's used for storage only,
not living (we haven't planning permission or whatever else is needed for
that). The house has benefited.
I need a new keyboard because I genuinely spluttered tea on my keyboard the
It did some very weird things and I thought I must have a virus, the
'faults' changed daily. There was a drop of liquid which moved over the
printed circuit under the keys, making new connections and macros from time
I was pleased when in deperation I tried another keyboard and it worked, I'd
tried all sorts of other tricks which didn't.
You've been warned!
I also need new spectacles, it comes to us all :-(
There is no intention of it becoming a 'room' - it's a big house with
plenty of space anyway. All I am talking about is the use of the loft
for storage, and only a central 'walkway' would be boarded (I would
guess at most one-quarter of the total area). On that basis, even if
we took the easy way out and dispensed with half the insulation
thickness over that area it wouldn't have a huge impact on the overall
thermal performance (especially considering that the 'liberated'
insulation material would be used to increase the thickness in some of
the non-boarded regions).
I did exactly that for a customer last week. A walkway 1:2m wide & 7m long
+ an area 1.2m x 1.2m behind the loft access. Nearly 10 sq mtrs of space,
but less than 25% of the floor area.
I told the customer that boarding the loft would reduce the effect of the
insulation & he didn't care, storage space was more important than 'saving
the planet' to him. Customers choice if I give him honest information.
I simply slit the insulation over the joists & tucked it down so the
chipboard panel laid flat. Compressing the insulation material obviously
has an effect on its ability to insulate, but 18mm chipboard has some
insulation value anyway.
Like many people he belives that most of the environmental 'we are doomed'
stuff is over hyped rubbish & wants to get on with his life.
We moved recently to a seventies bungalow with the same problem, and with
the added complication of a low headroom trussed roof, which I suspect you
do not have. It came with approx 4" of fairly new glass fibre insulation
between the trusses/joists, the original having been only an inch or so.
My compromise solution to improving the insulation without loosing too much
Glue and screw 2x2" timbers to the joists/truss tops, in the centre section
Buy a load of seconds of 50mm foil backed Kingspan boards via ebay. These
were cut to fit between the new 2x2"s in the centre area, and laid across
the joists in the outer areas.
Board the centre area only with 8x4 chipboard flooring above the kingspan.
I also lifted the existing insulation first, and laid strips of polythene as
a vapour barrier - this was done as a "sensible precaution" and was was
probably the worst part of the job.
This has made a noticeable difference - during the recent cold snap the part
of the house that has been completed was much warmer than the end that still
has mostly just the 4" glassfibre.
Despite this I have only lost 2.75" of headroom - which I can live with, and
the kinspan cover has noticeably reduced the glass particles that float in
the breeze, and make me cough. It also reduces wind losses of heat from loft
ventilation compared to a glass fibre surface (see Kingspan's info).
As for the weight loading of the chipboard - on arrival there was a 50
gallon watertank sitting over three trusses. I calculate this water load as
around 75 kg per truss, and there does not seem to have been a sag problem
over the last 35 odd years. The distributed weight of the boards should be
much less per truss. Incidentally the tank is now gone - heatbank.
I've made sure that high current wiring (rings, immersion, shower) are above
the insulation, but not worried too much about lighting, as there is more
margin for de-rating in a 6A/1mm circuit.
I realise that this solution is not fully to current building regs, but it
is equivalent to about 8" of glassfibre, and gives me a sensible amount of
storage and loft access. It may give you some ideas, but of course your own
solution is for you to find (legal bit!).
If you were to tuck the existing stuff between the joists, then lay a
board like you suggest over the joists, you could screw your flooring
down through it and would have no need for additional joists since it is
stiff enough to take the weight.
50mm "seconds" would be ideal for this sort of application. You could
probably get them at £12 per 8x4 sheet.
Last time I was in that situation, I gave the keyboard a shower and left
it in a warm place for a week. I am still typing on it now. There is
very little chance the water would cause any damage, unless the keyboard
had not dried out properly.
On Nov 22, 12:14 am, "The Medway Handyman" > has an effect on its
ability to insulate, but 18mm chipboard has some
Together with the layer of stuff being stored. In our case amongst
other things are clothes, bedding & countless layers of paper (pages
of books) which will insulate quite nicely.
Amen to that.