Im thinking of insulating some external solid walls using 2 layers of 25mm
celotex set overlapped between wall fixed 25mm battens, with plasterboard
over to fix it all in place.

Is it necessary to extend the celotex beneath the floor? Id assume it is
at the ceiling, but Im thinking the floor wont be as much of a cold
bridging opportunity.

Any links/guidance appreciated.

--

Cheers, Rob

On 31/05/2021 17:38, RJH wrote:

Im thinking of insulating some external solid walls using 2 layers of 25mm
celotex set overlapped between wall fixed 25mm battens, with plasterboard
over to fix it all in place.

Is it necessary to extend the celotex beneath the floor? Id assume it is
at the ceiling, but Im thinking the floor wont be as much of a cold
bridging opportunity.

Any links/guidance appreciated.


I did, but I used 30mm quinntherm which is more consistant,
and also you can cut down 89mm CLS timber nicely into
three battens of 30mm. Slap first layer onto wall, fix
30mm battens horizontally at top bottom and whereever
using frame anchors right through batten and 1st layer.
Infill with more 30mm celotex and then plasterboard.

On the ground floor I dug out all the screed and went
down to the slab and also did the floor with 3x2
battens infilled with 70mm quinntherm. Upstairs I
pulled up the chipboard flooring (unglued tongues
luckily) and insulated down to the ceiling below
(joists running side to side with a 2 inch gap at the
front wall).

IN my case the ground floor had a normal 65mm cavity
but the upper floor (facing north) was horrid hollow
9 inch blocks with the perps unmortared (!) and plastic
shiplap cladding and no building paper. These blocks started
above the ground floor window lintels and a course of horizontal
bricks bridged the cavity approximately where the
coving was. Appalling heat loss. Now I can keep the
lounge warm with just a 1 bar electric fire apart from
when we have severe northerly winds and blocking highs over
Russia.

Around the window reveals I made my own foil-backed
plasterboard with turkey foil and spray adhesive, ripped
off the galvanised mesh welded into the underside of the
lintel and glued the PB into place with foaming PU adhesive.
Ditto the sides of the reveal after removing existing plaster
while the wall kept its original plaster.

Also had to extend the BT incoming cable with a bit of
nifty soldering :-)

Andrew wrote:
On 31/05/2021 17:38, RJH wrote:

Im thinking of insulating some external solid walls using 2 layers of 25mm
celotex set overlapped between wall fixed 25mm battens, with plasterboard
over to fix it all in place.

Is it necessary to extend the celotex beneath the floor? Id assume it is
at the ceiling, but Im thinking the floor wont be as much of a cold
bridging opportunity.

Any links/guidance appreciated.


I did, but I used 30mm quinntherm which is more consistant,
and also you can cut down 89mm CLS timber nicely into
three battens of 30mm. Slap first layer onto wall, fix
30mm battens horizontally at top bottom and whereever
using frame anchors right through batten and 1st layer.
Infill with more 30mm celotex and then plasterboard.

On the ground floor I dug out all the screed and went
down to the slab and also did the floor with 3x2
battens infilled with 70mm quinntherm. Upstairs I
pulled up the chipboard flooring (unglued tongues
luckily) and insulated down to the ceiling below
(joists running side to side with a 2 inch gap at the
front wall).

IN my case the ground floor had a normal 65mm cavity
but the upper floor (facing north) was horrid hollow
9 inch blocks with the perps unmortared (!) and plastic
shiplap cladding and no building paper. These blocks started
above the ground floor window lintels and a course of horizontal
bricks bridged the cavity approximately where the
coving was. Appalling heat loss. Now I can keep the
lounge warm with just a 1 bar electric fire apart from
when we have severe northerly winds and blocking highs over
Russia.

Around the window reveals I made my own foil-backed
plasterboard with turkey foil and spray adhesive, ripped
off the galvanised mesh welded into the underside of the
lintel and glued the PB into place with foaming PU adhesive.
Ditto the sides of the reveal after removing existing plaster
while the wall kept its original plaster.

Also had to extend the BT incoming cable with a bit of
nifty soldering :-)


Many thanks - thorough job by the sounds of it, and plenty to go on. I had
thought of mini battens in the reveals - Ill rethink with the glue idea.

--

Cheers, Rob

RJH wrote:
Andrew wrote:
On 31/05/2021 17:38, RJH wrote:

Im thinking of insulating some external solid walls using 2 layers of 25mm
celotex set overlapped between wall fixed 25mm battens, with plasterboard
over to fix it all in place.

Is it necessary to extend the celotex beneath the floor? Id assume it is
at the ceiling, but Im thinking the floor wont be as much of a cold
bridging opportunity.

Any links/guidance appreciated.


I did, but I used 30mm quinntherm which is more consistant,
and also you can cut down 89mm CLS timber nicely into
three battens of 30mm. Slap first layer onto wall, fix
30mm battens horizontally at top bottom and whereever
using frame anchors right through batten and 1st layer.
Infill with more 30mm celotex and then plasterboard.

On the ground floor I dug out all the screed and went
down to the slab and also did the floor with 3x2
battens infilled with 70mm quinntherm. Upstairs I
pulled up the chipboard flooring (unglued tongues
luckily) and insulated down to the ceiling below
(joists running side to side with a 2 inch gap at the
front wall).

IN my case the ground floor had a normal 65mm cavity
but the upper floor (facing north) was horrid hollow
9 inch blocks with the perps unmortared (!) and plastic
shiplap cladding and no building paper. These blocks started
above the ground floor window lintels and a course of horizontal
bricks bridged the cavity approximately where the
coving was. Appalling heat loss. Now I can keep the
lounge warm with just a 1 bar electric fire apart from
when we have severe northerly winds and blocking highs over
Russia.

Around the window reveals I made my own foil-backed
plasterboard with turkey foil and spray adhesive, ripped
off the galvanised mesh welded into the underside of the
lintel and glued the PB into place with foaming PU adhesive.
Ditto the sides of the reveal after removing existing plaster
while the wall kept its original plaster.

Also had to extend the BT incoming cable with a bit of
nifty soldering :-)


Many thanks - thorough job by the sounds of it, and plenty to go on. I had
thought of mini battens in the reveals - Ill rethink with the glue idea.


Quick question - what distance did you use for batten spacing? The online
guides* seem to suggest 400mm. Thisd be fine for a stud partition but I
dont see the need on a solid wall. Id have thought using 1.2m spaced
vertical would be sufficient, easiest (noted you used horizontal) and
reduce cold bridging.

* https://www.diydoctor.org.uk/projects/batteningwall.htm

--

Cheers, Rob

On 02/06/2021 05:49, RJH wrote:
RJH wrote:
Andrew wrote:
On 31/05/2021 17:38, RJH wrote:

Im thinking of insulating some external solid walls using 2 layers of 25mm
celotex set overlapped between wall fixed 25mm battens, with plasterboard
over to fix it all in place.

Is it necessary to extend the celotex beneath the floor? Id assume it is
at the ceiling, but Im thinking the floor wont be as much of a cold
bridging opportunity.

Any links/guidance appreciated.


I did, but I used 30mm quinntherm which is more consistant,
and also you can cut down 89mm CLS timber nicely into
three battens of 30mm. Slap first layer onto wall, fix
30mm battens horizontally at top bottom and whereever
using frame anchors right through batten and 1st layer.
Infill with more 30mm celotex and then plasterboard.

On the ground floor I dug out all the screed and went
down to the slab and also did the floor with 3x2
battens infilled with 70mm quinntherm. Upstairs I
pulled up the chipboard flooring (unglued tongues
luckily) and insulated down to the ceiling below
(joists running side to side with a 2 inch gap at the
front wall).

IN my case the ground floor had a normal 65mm cavity
but the upper floor (facing north) was horrid hollow
9 inch blocks with the perps unmortared (!) and plastic
shiplap cladding and no building paper. These blocks started
above the ground floor window lintels and a course of horizontal
bricks bridged the cavity approximately where the
coving was. Appalling heat loss. Now I can keep the
lounge warm with just a 1 bar electric fire apart from
when we have severe northerly winds and blocking highs over
Russia.

Around the window reveals I made my own foil-backed
plasterboard with turkey foil and spray adhesive, ripped
off the galvanised mesh welded into the underside of the
lintel and glued the PB into place with foaming PU adhesive.
Ditto the sides of the reveal after removing existing plaster
while the wall kept its original plaster.

Also had to extend the BT incoming cable with a bit of
nifty soldering :-)


Many thanks - thorough job by the sounds of it, and plenty to go on. I had
thought of mini battens in the reveals - Ill rethink with the glue idea.


Quick question - what distance did you use for batten spacing? The online
guides* seem to suggest 400mm. Thisd be fine for a stud partition but I
dont see the need on a solid wall. Id have thought using 1.2m spaced
vertical would be sufficient, easiest (noted you used horizontal) and
reduce cold bridging.

* https://www.diydoctor.org.uk/projects/batteningwall.htm


I only used horizontal battens, about 400mm apart, plus a frame
aroundthe perimeter of the windows to support the 90 degree joint
in the plasterboard. The bottom batten was a spare 125mm x ?? cut down
to 30mm depth. Because the infill of the 2nd layer inside the battens
was flush with the batten surface, it provides extra impact resistance,
but I diy-skimmed it anyway, which wasn't the best result.

Andrew wrote:
On 02/06/2021 05:49, RJH wrote:
RJH wrote:
Andrew wrote:
On 31/05/2021 17:38, RJH wrote:

Im thinking of insulating some external solid walls using 2 layers of 25mm
celotex set overlapped between wall fixed 25mm battens, with plasterboard
over to fix it all in place.

Is it necessary to extend the celotex beneath the floor? Id assume it is
at the ceiling, but Im thinking the floor wont be as much of a cold
bridging opportunity.

Any links/guidance appreciated.


I did, but I used 30mm quinntherm which is more consistant,
and also you can cut down 89mm CLS timber nicely into
three battens of 30mm. Slap first layer onto wall, fix
30mm battens horizontally at top bottom and whereever
using frame anchors right through batten and 1st layer.
Infill with more 30mm celotex and then plasterboard.

On the ground floor I dug out all the screed and went
down to the slab and also did the floor with 3x2
battens infilled with 70mm quinntherm. Upstairs I
pulled up the chipboard flooring (unglued tongues
luckily) and insulated down to the ceiling below
(joists running side to side with a 2 inch gap at the
front wall).

IN my case the ground floor had a normal 65mm cavity
but the upper floor (facing north) was horrid hollow
9 inch blocks with the perps unmortared (!) and plastic
shiplap cladding and no building paper. These blocks started
above the ground floor window lintels and a course of horizontal
bricks bridged the cavity approximately where the
coving was. Appalling heat loss. Now I can keep the
lounge warm with just a 1 bar electric fire apart from
when we have severe northerly winds and blocking highs over
Russia.

Around the window reveals I made my own foil-backed
plasterboard with turkey foil and spray adhesive, ripped
off the galvanised mesh welded into the underside of the
lintel and glued the PB into place with foaming PU adhesive.
Ditto the sides of the reveal after removing existing plaster
while the wall kept its original plaster.

Also had to extend the BT incoming cable with a bit of
nifty soldering :-)


Many thanks - thorough job by the sounds of it, and plenty to go on. I had
thought of mini battens in the reveals - Ill rethink with the glue idea.


Quick question - what distance did you use for batten spacing? The online
guides* seem to suggest 400mm. Thisd be fine for a stud partition but I
dont see the need on a solid wall. Id have thought using 1.2m spaced
vertical would be sufficient, easiest (noted you used horizontal) and
reduce cold bridging.

* https://www.diydoctor.org.uk/projects/batteningwall.htm


I only used horizontal battens, about 400mm apart, plus a frame
aroundthe perimeter of the windows to support the 90 degree joint
in the plasterboard. The bottom batten was a spare 125mm x ?? cut down
to 30mm depth. Because the infill of the 2nd layer inside the battens
was flush with the batten surface, it provides extra impact resistance,
but I diy-skimmed it anyway, which wasn't the best result.


Grand, thanks.

--

Cheers, Rob