G'day.

Eventually I will start this project instead of just
worrying about it here!

I have this nice new roof on a single-storey extension,
and no ceiling (pulled it down and chucked it away).

Here is my plan, I would be grateful for advice and
criticism....

The room is 2.5 m x 4.0 m, with a roof that drops 80 cm
from one end to the other (i.e. 80cm in 4.0 m, making
the roof roughly 4.08 m long, measured along its length,
inside).

Put a 2.5 m wall plate at each end (one low, one high),
hang 4.1 m rafters/joists at 60 cm centres. Rafters to
be deep enough accomodate 130m insulation (statutory
to achieve 0.2 U-value), then battens and noggins below
the rafters for the plasterboard.

This ceiling is not to support anything but itself and
its insulation.

(An alternative, which is a flat and level ceiling, is not
acceptable because the low end is too low.

Another alternative would be to use long wall-plates
and short joists (across the room), but there are
structural irregularities that would make this difficult.
Virtually impossible for me!)

Is this plan any use? If so, are there building regs that
it needs to comply with? What sizes of timber do I need
for the wall plates and rafters/joists?

Thanks very much!
David Pearson

"David Pearson" wrote in message
...
G'day.

Eventually I will start this project instead of just
worrying about it here!

I have this nice new roof on a single-storey extension,
and no ceiling (pulled it down and chucked it away).

Here is my plan, I would be grateful for advice and
criticism....

The room is 2.5 m x 4.0 m, with a roof that drops 80 cm
from one end to the other (i.e. 80cm in 4.0 m, making
the roof roughly 4.08 m long, measured along its length,
inside).

Put a 2.5 m wall plate at each end (one low, one high),
hang 4.1 m rafters/joists at 60 cm centres. Rafters to
be deep enough accomodate 130m insulation (statutory
to achieve 0.2 U-value), then battens and noggins below
the rafters for the plasterboard.

This ceiling is not to support anything but itself and
its insulation.

(An alternative, which is a flat and level ceiling, is not
acceptable because the low end is too low.

Another alternative would be to use long wall-plates
and short joists (across the room), but there are
structural irregularities that would make this difficult.
Virtually impossible for me!)

Is this plan any use? If so, are there building regs that
it needs to comply with? What sizes of timber do I need
for the wall plates and rafters/joists?

Thanks very much!
David Pearson


If it's just a flat level ceiling you want, then why not go for a suspended
one. These are light weight, but strong enough to support lagging for the U
value requirements. They're also strong enough to hang lighting in and on
them if needs be.

Making a heavy timber structure if it's not really needed is a way to much
over engineering, in my opinion anyway, and you'd get away with a light
weight suspended ceiling without all that hassle.

BigWallop wrote:

Making a heavy timber structure if it's not really needed is a way to much
over engineering, in my opinion anyway, and you'd get away with a light
weight suspended ceiling without all that hassle.

how do you make those then?

NT

"BigWallop" wrote in message
k...

If it's just a flat level ceiling you want, then why not go for a
suspended
one. These are light weight, but strong enough to support lagging for the
U
value requirements. They're also strong enough to hang lighting in and on
them if needs be.

Thanks Big Wallop, but I cannot have a flat level ceiling because
the low end of the roof is too low to allow that. I am not tall, but
the low end is still a bit close to my head.

Can a suspended ceiling be done on a slope? The hangars would
have to be vertical but not perpendicular to the rafters. Can it be
mastic'd to the wall to prevent heat loss through air movement?

Thanks,
David P.

"David Pearson" wrote in message
...

"BigWallop" wrote in message
k...

If it's just a flat level ceiling you want, then why not go for a
suspended
one. These are light weight, but strong enough to support lagging for
the
U
value requirements. They're also strong enough to hang lighting in and
on
them if needs be.

Thanks Big Wallop, but I cannot have a flat level ceiling because
the low end of the roof is too low to allow that. I am not tall, but
the low end is still a bit close to my head.

Can a suspended ceiling be done on a slope? The hangars would
have to be vertical but not perpendicular to the rafters. Can it be
mastic'd to the wall to prevent heat loss through air movement?

Thanks,
David P.


Are the roof beams on an angle as well? You could place the flat part of
the suspended ceiling at a good height for the room, remembering that the
minimum height for a ceiling is 2,400 mm (2.4 mtrs), and the lower part of
the beams can be plaster-boarded on the angle to hide the rest of them. Or
you could just plaster-board across the original beams themselves, instead
of dropping the height any more.

A suspended ceiling can be as simple as lengths of timber fixed to wire or
timber hangers fixed from the beams. Light-Weight timber can be 25 mm X 50
mm lengths just enough to screw plaster-board on to. That's if the ceiling
isn't going to take any other weight but its own and some light fittings.

"BigWallop" wrote in message
. uk...

Are the roof beams on an angle as well? You could place the flat part of
the suspended ceiling at a good height for the room, remembering that the
minimum height for a ceiling is 2,400 mm (2.4 mtrs), and the lower part of
the beams can be plaster-boarded on the angle to hide the rest of them.
Or
you could just plaster-board across the original beams themselves, instead
of dropping the height any more.

The beams, about 4.0 m long, are indeed on an angle.
The long axis (about 4 m) of the room runs east-west,
the short axis (2.5 m) north-south. The roof drops about
80 cm from the west end (high) to the east end (low),
so the roof beams do the same. (There is another room
the same size and same orientation in the extension, but
I am working one room at a time.)

What I wanted to do was this: put the 130mm (or similar
correct value, it is about that size) between the roof beams.
And then plasterboard under the insulation and beams. But if I do
put insulation between the roof beams (rafters), then the
ventilation across-rafters will be blocked. That is why I
need a ceiling lower than the roof beams - to install the
insulation while leaving ventilation space between the
ceiling and tiles.

So it is tiles (and sarking and counter battens and stuff)
at the top;
rafters below that, with good eaves ventilation but
only one tile vent in each room;
then I put the new ceiling below the rafters, and attach
the insulation, plasterboard and light fittings to the new
ceiling.


A suspended ceiling can be as simple as lengths of timber fixed to wire or
timber hangers fixed from the beams. Light-Weight timber can be 25 mm X
50
mm lengths just enough to screw plaster-board on to. That's if the
ceiling
isn't going to take any other weight but its own and some light fittings.

This sounds ideal, if only I can hang it from my sloping roof, and
seal it against the walls for insulation purposes.

Big Wallop, I sure do appreciate your helping out with this advice.

-DP.

"David Pearson" wrote in message
...

What I wanted to do was this: put the 130mm (or similar
correct value, it is about that size) between the roof beams.

I missed out the most important word here. Should read:

"What I wanted to do was this: put the 130mm *insulation* (or similar
correct value, it is about that size) between the roof beams."

Thanks,
Pearson

wrote:
BigWallop wrote:

Making a heavy timber structure if it's not really needed is a way to much
over engineering, in my opinion anyway, and you'd get away with a light
weight suspended ceiling without all that hassle.

how do you make those then?

Suspended ceilings are the easiest sort to make.
"I'll put a ceiling up there soon, really."

"David Pearson" wrote in message
...

"David Pearson" wrote in message
...

What I wanted to do was this: put the 130mm (or similar
correct value, it is about that size) between the roof beams.

I missed out the most important word here. Should read:

"What I wanted to do was this: put the 130mm *insulation* (or similar
correct value, it is about that size) between the roof beams."

Thanks,
Pearson

If the roof beams are that low from the ceiling to floor height, then why
not put lagging directly between them? You can then directly plaster-board
over the whole thing. No need for a false or suspended ceiling at all, and
I'm sure the insulation values would be enough for the size of the rooms.
It would also give you loads more head room and let you stretch your arms up
in the mornings. :-)

Ian Stirling wrote:
wrote:
BigWallop wrote:

Making a heavy timber structure if it's not really needed is a way to much
over engineering, in my opinion anyway, and you'd get away with a light
weight suspended ceiling without all that hassle.

how do you make those then?

Suspended ceilings are the easiest sort to make.
"I'll put a ceiling up there soon, really."

"BigWallop" wrote in message
. uk...
If the roof beams are that low from the ceiling to floor height, then why
not put lagging directly between them? You can then directly
plaster-board
over the whole thing. No need for a false or suspended ceiling at all,
and
I'm sure the insulation values would be enough for the size of the rooms.
It would also give you loads more head room and let you stretch your arms
up
in the mornings. :-)

Good morning.

That is what I had hoped to do, but: if I put the insulation
between the roof beams, then that will stop the air circulating
around between the roof beams.

I have a full-length eaves vent (well, the roof does anyway
and one tile vent that vents one between-the-beams gap. If I
fill all the gaps with insulation (apart from the 50 mm required
space at the top), then only that single between-the-beams
space will be ventilated. The others will not.

That's why I think I need to have the insulation held up by a
separate ceiling completely separate from the roof beams.

Cheers,
DP.

David Pearson wrote:

"BigWallop" wrote in message
. uk...

If the roof beams are that low from the ceiling to floor height, then why
not put lagging directly between them? You can then directly
plaster-board
over the whole thing. No need for a false or suspended ceiling at all,
and
I'm sure the insulation values would be enough for the size of the rooms.
It would also give you loads more head room and let you stretch your arms
up
in the mornings. :-)


Good morning.

That is what I had hoped to do, but: if I put the insulation
between the roof beams, then that will stop the air circulating
around between the roof beams.

I have a full-length eaves vent (well, the roof does anyway
and one tile vent that vents one between-the-beams gap. If I
fill all the gaps with insulation (apart from the 50 mm required
space at the top), then only that single between-the-beams
space will be ventilated. The others will not.

That's why I think I need to have the insulation held up by a
separate ceiling completely separate from the roof beams.


The way my BCO expected me to achieve what you have was by using less
celotex between the beams than the depth allowed.

I used 75mm on a 100mm depth rafter.

This allows a 25mm airspace over the top.

In my case I also had a void at the ridge - the ceilings were not
carried all the way up - and so the ridge vents provided efflux for the
whole area.

This is pretty much 'standard practice' for a 'cold roof' with a storey
built under the eaves.

I've missed the first part of this thread, but if its possible, and you
are attempting what I think you are - insulating and boarding out a loft
cavity in a cold roof style house - I would do it this way.

Put some horizontal timbers across the rafters up near the ridge.

Now cut and wedge as much celotex as you can fit between the rafters and
between the new horizontals, and tape ultra carefully using the metal
tape you buy for this purpose. The tape goes over the joists and onto
the celotex. The purpose is to form a complete airtight and moisture
tight barrier round the whole place. That stops cold air getting in, and
warm moist air getting onto your cold nbeams, condensing and causing rot.


Then simply plasterboard up, paper or skim, and paint.

You have about a 25mm gap above the insulation from the eaves vents to
the new tunnel formed by the ridge and the new horizontals and your
ridge vents will'exhaust' that. The BCO will be happy, and with all
draughts sealed out, so will you.

One caveat: With no way to allow moisture to escape from the living
area, the BCO will insist on some kind of background ventilation
'achievable in a secure manner' - usally without opening a window, so
you may need to punch holes in walls and use trickle vents etc. to allow
fresh air in and sweaty air out.




Cheers,
DP.

"The Natural Philosopher" wrote in message
t...

The way my BCO expected me to achieve what you have was by using less
celotex between the beams than the depth allowed.

Before I get back on topic... I was thinking of following
the BC regs carefully, and therefore did not think I needed
to involve a BCO. I will photograph the project as it
progresses (if it ever does!) to provide evidence that
everything conforms with the regs, in case I get inspected
in future.

Is this OK, or do I need to get a BCO in at the start?

In my case I also had a void at the ridge - the ceilings were not carried
all the way up - and so the ridge vents provided efflux for the whole
area.

This is pretty much 'standard practice' for a 'cold roof' with a storey
built under the eaves.

Thanks for this, but ... I can't do the same thing. The extension has
a lean-to design, so the top of the roof abuts the end-wall of the house,
a long way below the house's eaves. It was originally a garage.
(There is a whole BCO nightmare there, but that is a separate
issue!) So it has no ridge and no ridge-vents.

Instead, it has full-length eaves-vents and two tile-vents.
So if I fill up the gaps between the roof-beams (leaving a
space below the sarking etc.), then the gap that the tile vent
is in (one tile-vent in each room, I am only talking about
one room for now) will be ventilated by the eaves-vent and
tile-vent, but the others will only be ventilated by the
eaves-vent.

So it seems that I can't put the Celotex/whatever between
the roof-beams - I need a space that allows the gaps between
the roof-beams to "talk to each other".

I've missed the first part of this thread, but if its possible, and you
are attempting what I think you are - insulating and boarding out a loft
cavity in a cold roof style house - I would do it this way.

Thanks again, but this is not the situation. I am just trying
to put a ceiling in a one-storey extension, with the regulation
amount of insulation (by U-value), having got a new roof
on the extension.

One caveat: With no way to allow moisture to escape from the living area,
the BCO will insist on some kind of background ventilation 'achievable in
a secure manner' - usally without opening a window, so you may need to
punch holes in walls and use trickle vents etc. to allow fresh air in and
sweaty air out.

I had not though of that one. Maybe this is a good reason to
get a BCO in? I can read the regulations, but I might miss
stuff that an experienced builder knows about.

Regards,
David Pearson.

"David Pearson" wrote in message
...

"The Natural Philosopher" wrote in message
t...

The way my BCO expected me to achieve what you have was by using less
celotex between the beams than the depth allowed.

Before I get back on topic... I was thinking of following
the BC regs carefully, and therefore did not think I needed
to involve a BCO. I will photograph the project as it
progresses (if it ever does!) to provide evidence that
everything conforms with the regs, in case I get inspected
in future.

Is this OK, or do I need to get a BCO in at the start?

In my case I also had a void at the ridge - the ceilings were not
carried
all the way up - and so the ridge vents provided efflux for the whole
area.

This is pretty much 'standard practice' for a 'cold roof' with a storey
built under the eaves.

Thanks for this, but ... I can't do the same thing. The extension has
a lean-to design, so the top of the roof abuts the end-wall of the house,
a long way below the house's eaves. It was originally a garage.
(There is a whole BCO nightmare there, but that is a separate
issue!) So it has no ridge and no ridge-vents.

Instead, it has full-length eaves-vents and two tile-vents.
So if I fill up the gaps between the roof-beams (leaving a
space below the sarking etc.), then the gap that the tile vent
is in (one tile-vent in each room, I am only talking about
one room for now) will be ventilated by the eaves-vent and
tile-vent, but the others will only be ventilated by the
eaves-vent.

So it seems that I can't put the Celotex/whatever between
the roof-beams - I need a space that allows the gaps between
the roof-beams to "talk to each other".

I've missed the first part of this thread, but if its possible, and you
are attempting what I think you are - insulating and boarding out a loft
cavity in a cold roof style house - I would do it this way.

Thanks again, but this is not the situation. I am just trying
to put a ceiling in a one-storey extension, with the regulation
amount of insulation (by U-value), having got a new roof
on the extension.

One caveat: With no way to allow moisture to escape from the living
area,
the BCO will insist on some kind of background ventilation 'achievable
in
a secure manner' - usally without opening a window, so you may need to
punch holes in walls and use trickle vents etc. to allow fresh air in
and
sweaty air out.

I had not though of that one. Maybe this is a good reason to
get a BCO in? I can read the regulations, but I might miss
stuff that an experienced builder knows about.

Regards,
David Pearson.

I still think it'd be easier getting something like this
http://www.lafargeplasterboard.co.uk/images/lib/175.jpg I'd say. So much
lighter in weight, and doesn't need any special fitting techniques. Once
the plaster-board is up you fill above with your lagging system, and the
jobs done. No huge timber weight involved. No humphing and grumphing with
timber joists and huge wall fixings. So much easier all the way through.

"BigWallop" wrote in message
. uk...

I still think it'd be easier getting something like this
http://www.lafargeplasterboard.co.uk/images/lib/175.jpg I'd say. So much
lighter in weight, and doesn't need any special fitting techniques. Once
the plaster-board is up you fill above with your lagging system, and the
jobs done. No huge timber weight involved. No humphing and grumphing
with
timber joists and huge wall fixings. So much easier all the way through.


I love it!


Thanks Professor Wallop and everyone else who has
educated me about all these things.


-David P.