Hi,

I am interested in boarding over part of my loft area, in order to
increase the
amount of storage space in our house. My question is concerning
insulation.
The joists on the floor of the loft are 3x2, thus if I put boarding
directly
on to them, I can only have a maximum of 3" of insulation (I think I
should have a lot more ?!) Should I screw some lengths of 3x2 or 4x2
at right angles to the joists, place extra insulation in the spaces.
and then board on top of these ? I know I will lose a small amount of
height, and it will cost a bit more, but the house is a 30's semi
(with no cavity walls) so I would like to get the loft fairly well
insulated.

Would I also need to put in some form of damp membrane ? The roof is
not felted, so there is quite a bit (!) of air flow through the roof
space. I was not going to board over the complete area, so would it be
ok to not put down a membrane on the warm side of the insualtion ?

Any comments appreciated..

Paul..

"Wordy" wrote in message
om...
Hi,

I am interested in boarding over part of my loft area, in order to
increase the
amount of storage space in our house. My question is concerning
insulation.
The joists on the floor of the loft are 3x2, thus if I put boarding
directly
on to them, I can only have a maximum of 3" of insulation (I think I
should have a lot more ?!) Should I screw some lengths of 3x2 or 4x2
at right angles to the joists, place extra insulation in the spaces.
and then board on top of these ? I know I will lose a small amount of
height, and it will cost a bit more, but the house is a 30's semi
(with no cavity walls) so I would like to get the loft fairly well
insulated.

Would I also need to put in some form of damp membrane ? The roof is
not felted, so there is quite a bit (!) of air flow through the roof
space. I was not going to board over the complete area, so would it be
ok to not put down a membrane on the warm side of the insualtion ?

Any comments appreciated..

Paul..

First comment is to check your floor loadings - 3 * 2 won't carry much
weight.
[By that I mean that it wouldn't carry the kind of load you would put on an
average floor - so if you plan to stack heavy things and walk on it as well
you could be in for a surprise]
The building regs. carry tables which show maximum load for cross section
and span and spacing for beams.

I don't know if additional beams at right angles will increase the load
bearing capacity by spreading any load, or just count as additional weight
on your original 3*2 beams/joists and reduce the amount you can store. I
assume that of you screw at every joist this may provide a more rigid
structure.

If you screw additional joists along the top of your existing ones (e.g. add
another 3*2 to make a nominal 6*2 joist) that may help but it won't be as
strong as a single 6*2 joist.

For loft conversions they put in a new load bearing structure - but this is
way OTT for a bit of extra storage :-)

Alternatives are to use more efficient insulation e.g. Celotex between your
3*2 joists but this is likely to be expensive.

All very imprecise, I am afraid.

Cheers
Dave R

I am interested in boarding over part of my loft area, in order
to increase the amount of storage space in our house.

Consider insulating the roof instead. Then you get a warm loft situation,
which is better for your stored items and any water pipes passing through.
If you do so, ensure you pay adequete attention to the ventilation of the
rafters, or you might get rot.

Christian.

In message ,
"Christian McArdle" wrote:

I am interested in boarding over part of my loft area, in order
to increase the amount of storage space in our house.

Consider insulating the roof instead. Then you get a warm loft situation,
which is better for your stored items and any water pipes passing through.
If you do so, ensure you pay adequete attention to the ventilation of the
rafters, or you might get rot.


This is something that has got me thinking - what with moving house and
everything. I *could* insulate in the plane of the roof, but with
ventillated eaves this isn't going to help the warmth of the house much.
However, if I block the eaves, how can I keep the roof structure in good
nick?

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Don't fight technology, live with it: http://www.livtech.co.uk/
.... I haven't lost my mind; it's backed up on tape somewhere!

Wordy wrote:
Hi,

I am interested in boarding over part of my loft area, in order to
increase the
amount of storage space in our house. My question is concerning
insulation.
The joists on the floor of the loft are 3x2, thus if I put boarding
directly
on to them, I can only have a maximum of 3" of insulation (I think I
should have a lot more ?!) Should I screw some lengths of 3x2 or 4x2
at right angles to the joists, place extra insulation in the spaces.
and then board on top of these ? I know I will lose a small amount of
height, and it will cost a bit more, but the house is a 30's semi
(with no cavity walls) so I would like to get the loft fairly well
insulated.

Would I also need to put in some form of damp membrane ? The roof is
not felted, so there is quite a bit (!) of air flow through the roof
space. I was not going to board over the complete area, so would it be
ok to not put down a membrane on the warm side of the insualtion ?

Any comments appreciated..

Paul..

Beware of such joists. I've seen a case where long cracks appeared in
upstairs ceiling due to loading of stored items in boarded loft. The cracks
were exactly underneath the joists ...

Martin Angove wrote:

In message ,
"Christian McArdle" wrote:


I am interested in boarding over part of my loft area, in order
to increase the amount of storage space in our house.

Consider insulating the roof instead. Then you get a warm loft situation,
which is better for your stored items and any water pipes passing through.
If you do so, ensure you pay adequete attention to the ventilation of the
rafters, or you might get rot.



This is something that has got me thinking - what with moving house and
everything. I *could* insulate in the plane of the roof, but with
ventillated eaves this isn't going to help the warmth of the house much.
However, if I block the eaves, how can I keep the roof structure in good
nick?


Standard trick is to use celotex between rafters and allow the draught
to go over the top of it: You then seal between celotex and loft floor
at eave level.


Hwyl!

M.

"BillR" wrote in message
...
Wordy wrote:
Hi,

I am interested in boarding over part of my loft area, in order to
increase the
amount of storage space in our house. My question is concerning
insulation.

I'm also interested in doing this, though I have 6" joists. I'd be
interested to know when / if a damp-proof membrane is required and if anyone
knows a cheap / reliable supplier of celotex insulation? What thickness of
celotex would be reasonable (has anyone else done the calculations)?!

Thanks!

Leigh

I *could* insulate in the plane of the roof, but with ventillated
eaves this isn't going to help the warmth of the house much.

The open eaves are good. You make sure they enter the ventilation space
between the roof covering and the insulation. You may also need ridge
ventilation, especially if you have ridge boards or a half roof.

Christian.

I'm also interested in doing this, though I have 6" joists.

With 6 inch joists, you are laughing. If you can afford celotex, just use
the complete thickness and board over if you wish. Alternatively, a 25mm
section cross layed over the top will reduce cold bridging through the
joists. The damp proof membrane goes under the insulation. If you are doing
it from scratch, it goes between the plasterboard and joists. If the ceiling
is already in place, use plastic sheet over the joists, but under the
insulation.

and if anyone knows a cheap / reliable supplier of celotex insulation?

www.seconds.co.uk

Christian.

L Reid wrote:

"BillR" wrote in message
...

Wordy wrote:

Hi,

I am interested in boarding over part of my loft area, in order to
increase the
amount of storage space in our house. My question is concerning
insulation.


I'm also interested in doing this, though I have 6" joists. I'd be
interested to know when / if a damp-proof membrane is required and if anyone
knows a cheap / reliable supplier of celotex insulation? What thickness of
celotex would be reasonable (has anyone else done the calculations)?!


(i) Celotex incorporates its own foil damp proof coating. Use foil tape
to seal it to joists etc.


(ii) There are no cheap suppliers of Celotex.

(iii) 50mm is a minimum thickness, 75mm is equivalent to 6" of rockwool.
Well into top regulatrory requrements. However the joists form a 'cold
bridge and ANY tiny draughts will reduce effectiveness, so its not all
roses.





Thanks!

Leigh

Christian McArdle wrote:

I'm also interested in doing this, though I have 6" joists.


With 6 inch joists, you are laughing. If you can afford celotex, just use
the complete thickness and board over if you wish.


You should not do that - the regs insist on an airgap to allow air to
circulate over the joitsts etc.

In my case they insited on eave (soffit) vents and where I had
impervious sarking, ridge vents as well.

Alternatively, a 25mm
section cross layed over the top will reduce cold bridging through the
joists. The damp proof membrane goes under the insulation. If you are doing
it from scratch, it goes between the plasterboard and joists. If the ceiling
is already in place, use plastic sheet over the joists, but under the
insulation.


and if anyone knows a cheap / reliable supplier of celotex insulation?


www.seconds.co.uk

Christian.

With 6 inch joists, you are laughing. If you can afford celotex, just use
the complete thickness and board over if you wish.


You should not do that - the regs insist on an airgap to allow air to
circulate over the joitsts etc.

How can you have a floor, if you must leave an air gap between the joists
and the boards?

Can I presume you thought I was still talking about insulating the roof, not
the floor?

Christian.

Christian McArdle wrote:

With 6 inch joists, you are laughing. If you can afford celotex, just use
the complete thickness and board over if you wish.


You should not do that - the regs insist on an airgap to allow air to
circulate over the joitsts etc.


How can you have a floor, if you must leave an air gap between the joists
and the boards?

Can I presume you thought I was still talking about insulating the roof, not
the floor?



Yes. Sorry.


Christian.

"The Natural Philosopher" wrote in message
...
Christian McArdle wrote:

With 6 inch joists, you are laughing. If you can afford celotex, just
use
the complete thickness and board over if you wish.


You should not do that - the regs insist on an airgap to allow air to
circulate over the joitsts etc.


How can you have a floor, if you must leave an air gap between the
joists
and the boards?

Can I presume you thought I was still talking about insulating the roof,
not
the floor?



Yes. Sorry.


Christian.







Thanks for all replies. I fancy using Celotex as I also need to do some
angled sections which won't be the easiest to get into. Might try and take a
couple of photos at the weekend to give people a better idea of what I'm
after, but the replies so far are what I was after!

Leigh