A BT rewire has made an extension socket in the kitchen redundant. I've
removed the back box, but am wondering about the best way to fill the
hole before repainting. The hole is about 70 x 70 x 25mm.

I've got enough polyfilla, but it would take several layers allowing it
to dry in between. Or I could partially fill the hole with mortar and
let that dry before using filler. I've even considered putting the back
box in back-to-front and using a thin layer (2 - 3 mm) of filler over
it. Would the thin layer be strong enough? Could something else like
expanded polystyrene be used to partially fill the hole before using filler?

--
Jeff

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 03/03/2025 08:48, Jeff Layman wrote:

A BT rewire has made an extension socket in the kitchen redundant. I've removed the back box, but am wondering about the best way to fill the
hole before repainting. The hole is about 70 x 70 x 25mm.

I've got enough polyfilla, but it would take several layers allowing it
to dry in between. Or I could partially fill the hole with mortar and
let that dry before using filler. I've even considered putting the back
box in back-to-front and using a thin layer (2 - 3 mm) of filler over
it. Would the thin layer be strong enough? Could something else like
expanded polystyrene be used to partially fill the hole before using
filler?

Irrespective of what you use its not going to be a one off application.

To avoid the possibility of cracking, especially around the perimeter of
the hole, seal it with a 50:50 PVA:water mix and allow to dry. Unsealed
Old brick or plaster surrounding the infill will suck the water/moisture
out of whatever you use and its liable to crack at that point during the
drying process.

A thin layer over a reversed back-box in unlikely to be satisfactory.

As suggested in another answer a bit of brick or stones or similar to
bulk out the infill means that you can use much less filler.

You could use mortar or your polyfiller to secure your infill -
whichever is more convenient, handy, cheaper. Make sure that the infill
is a few mm below the finished surface. Let it dry.

Even when you fill flush the filler may shrink back slightly when it
dries requiring another light skim over the top. It helps if your trowel
you are using for the final layers is wider than the hole you are filling.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Jeff Layman wrote:

A BT rewire has made an extension socket in the kitchen redundant. I've removed the back box, but am wondering about the best way to fill the
hole before repainting. The hole is about 70 x 70 x 25mm.

I've got enough polyfilla, but it would take several layers allowing it
to dry in between. Or I could partially fill the hole with mortar and
let that dry before using filler. I've even considered putting the back
box in back-to-front and using a thin layer (2 - 3 mm) of filler over
it. Would the thin layer be strong enough? Could something else like
expanded polystyrene be used to partially fill the hole before using
filler?

- Paint inside of hole with dilute PVA.
- When PVA is dry (about an hour) fill hole with bonding plaster (may be
called undercoat plaster in the sheds), leave surface slightly (about a
mm) below wall surface.
- Next day (or later) use your polyfilla to fill the remaining shallow depression, get it as flat as you can.
- When polyfilla is dry (next day?) sand it flat by wrapping 120g
sandpaper around a piece of wood that's long enough to bridge across the
hole.
- Repeat the last 2 stages if the result isn't as good as you want.
- paint with diluted finish paint, then a couple of undiluted coats.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 03/03/2025 08:48, Jeff Layman wrote:

A BT rewire has made an extension socket in the kitchen redundant. I've removed the back box, but am wondering about the best way to fill the
hole before repainting. The hole is about 70 x 70 x 25mm.

I've got enough polyfilla, but it would take several layers allowing it
to dry in between. Or I could partially fill the hole with mortar and
let that dry before using filler. I've even considered putting the back
box in back-to-front and using a thin layer (2 - 3 mm) of filler over
it. Would the thin layer be strong enough? Could something else like
expanded polystyrene be used to partially fill the hole before using
filler?

I have many methods
E.g. (if you have some handy) use a piece of plasterboard wedged in the
hole below the surface of the finished wall and skim. There are many
other ways to do the wedging.
Simply get ANYTHING that will support the first bodge coat of plaster - scrunched newspaper newspaper, a blown up balloon, used condoms,
expanding foam, and old bit of expanded foam packaging, or PU insulating
foam.

All it has to do is support the plaster till it sets.
And don't use polyfilla - its way quicker to use several coats of fast
setting plaster.
--
“Some people like to travel by train because it combines the slowness of
a car with the cramped public exposure of 
an airplane.”

Dennis Miller

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 03/03/2025 15:34, The Natural Philosopher wrote:

On 03/03/2025 08:48, Jeff Layman wrote:

A BT rewire has made an extension socket in the kitchen redundant.
I've removed the back box, but am wondering about the best way to fill
the hole before repainting. The hole is about 70 x 70 x 25mm.

I've got enough polyfilla, but it would take several layers allowing
it to dry in between. Or I could partially fill the hole with mortar
and let that dry before using filler. I've even considered putting the
back box in back-to-front and using a thin layer (2 - 3 mm) of filler
over it. Would the thin layer be strong enough? Could something else
like expanded polystyrene be used to partially fill the hole before
using filler?

I have many methods
E.g. (if you have some handy) use a piece of plasterboard wedged in the
hole below the surface of the finished wall and skim. There are many
other  ways to do the wedging.
Simply get ANYTHING that will support the first bodge coat of plaster - scrunched newspaper newspaper, a blown up balloon, used condoms,
expanding foam, and old bit of expanded foam packaging, or PU insulating foam.

All it has to do is support the plaster till it sets.
And don't use polyfilla - its way quicker to use several coats of fast setting plaster.

But often the best material for speed of setting (curing or air drying)
doesn't come in small packs at a reasonable price, especially if being
used for a one off small job.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

The Natural Philosopher wrote:

On 03/03/2025 08:48, Jeff Layman wrote:

A BT rewire has made an extension socket in the kitchen redundant.
I've removed the back box, but am wondering about the best way to fill
the hole before repainting. The hole is about 70 x 70 x 25mm.

I've got enough polyfilla, but it would take several layers allowing
it to dry in between. Or I could partially fill the hole with mortar
and let that dry before using filler. I've even considered putting the
back box in back-to-front and using a thin layer (2 - 3 mm) of filler
over it. Would the thin layer be strong enough? Could something else
like expanded polystyrene be used to partially fill the hole before
using filler?

I have many methods
E.g. (if you have some handy) use a piece of plasterboard wedged in the
hole below the surface of the finished wall and skim. There are many
other  ways to do the wedging.
Simply get ANYTHING that will support the first bodge coat of plaster - scrunched newspaper newspaper, a blown up balloon, used condoms,
expanding foam, and old bit of expanded foam packaging, or PU insulating foam.

All it has to do is support the plaster till it sets.
And don't use polyfilla - its way quicker to use several coats of fast setting plaster.

I agree that polyfilla is not the best but the chap said he had some,
and it will do the job. What won't work well is to fill the whole hole
with the stuff.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 03/03/2025 11:33, No mail wrote:

Jeff Layman wrote:

A BT rewire has made an extension socket in the kitchen redundant.
I've removed the back box, but am wondering about the best way to fill
the hole before repainting. The hole is about 70 x 70 x 25mm.

I've got enough polyfilla, but it would take several layers allowing
it to dry in between. Or I could partially fill the hole with mortar
and let that dry before using filler. I've even considered putting the
back box in back-to-front and using a thin layer (2 - 3 mm) of filler
over it. Would the thin layer be strong enough? Could something else
like expanded polystyrene be used to partially fill the hole before
using filler?

- Paint inside of hole with dilute PVA.
- When PVA is dry (about an hour) fill hole with bonding plaster (may be called undercoat plaster in the sheds), leave surface slightly (about a
mm) below wall surface.
- Next day (or later) use your polyfilla to fill the remaining shallow depression, get it as flat as you can.
- When polyfilla is dry (next day?) sand it flat by wrapping 120g
sandpaper around a piece of wood that's long enough to bridge across the hole.
- Repeat the last 2 stages if the result isn't as good as you want.
- paint with diluted finish paint, then a couple of undiluted coats.

+1

But I keep an out-of-date bag of Wickes multi surface filler
for small, quick jobs like this.

PS, why bother to remove the back box ?.

As long as it is not sticking out above the surface, just
fill it with whatever old filler is to hand or mix some
old filler with sand/cement for first fill.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 03/03/2025 18:17, alan_m wrote:

On 03/03/2025 15:34, The Natural Philosopher wrote:

On 03/03/2025 08:48, Jeff Layman wrote:

A BT rewire has made an extension socket in the kitchen redundant.
I've removed the back box, but am wondering about the best way to
fill the hole before repainting. The hole is about 70 x 70 x 25mm.

I've got enough polyfilla, but it would take several layers allowing
it to dry in between. Or I could partially fill the hole with mortar
and let that dry before using filler. I've even considered putting
the back box in back-to-front and using a thin layer (2 - 3 mm) of
filler over it. Would the thin layer be strong enough? Could
something else like expanded polystyrene be used to partially fill
the hole before using filler?

I have many methods
E.g. (if you have some handy) use a piece of plasterboard wedged in
the hole below the surface of the finished wall and skim. There are
many other  ways to do the wedging.
Simply get ANYTHING that will support the first bodge coat of plaster
- scrunched newspaper newspaper, a blown up balloon, used condoms,
expanding foam, and old bit of expanded foam packaging, or PU
insulating foam.

All it has to do is support the plaster till it sets.
And don't use polyfilla - its way quicker to use several coats of fast
setting plaster.

But often the best material for speed of setting (curing or air drying) doesn't come in small packs at a reasonable price, especially if being
used for a one off small job.

It comes in small enough packs.

And is cheaper than polyfilla.

Thats why people dont skim walls with polyfilla

https://www.wickes.co.uk/British-Gypsum-Thistle-Multi-Finish-Plaster---25kg/p/220056

--
"First, find out who are the people you can not criticise. They are your oppressors."
- George Orwell

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 03/03/2025 20:13, The Natural Philosopher wrote:

And is cheaper than polyfilla.

Thats why people dont skim walls with polyfilla

https://www.wickes.co.uk/British-Gypsum-Thistle-Multi-Finish- Plaster---25kg/p/220056

Just what I used last week for a much bigger repair but now I have
probably 20kg left that will go off before I need it again.

What I've always found in the sheds that the outside of the bags are
always covered in plaster dust which will get on you clothes :)

The excess will now be sprinkled on the lawn :)

Previously I did manage to keep some, and usable, for nearly two years
packed very tightly to the top of an airtight container. After partially filling the container was vibrated to remove air pockets and to pack
down the plaster powder. This was repeated until I couldn't get any more in.

I've also kept old plaster for fixing in back boxes but I've had to work
fast as it will go off within 5 minutes.


--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 4 Mar 2025 at 14:43:08 GMT, Roger Mills wrote:

But often the best material for speed of setting (curing or air
drying) doesn't come in small packs at a reasonable price, especially
if being used for a one off small job.

It comes in small enough packs.

And is cheaper than polyfilla.

Thats why people dont skim walls with polyfilla

https://www.wickes.co.uk/British-Gypsum-Thistle-Multi-Finish-
Plaster---25kg/p/220056

What do you do with the remaining 24.9 Kg?

I find it lasts years if wrapped - but it goes off quickly and is only useful for basic filling.

--
Cheers, Rob, Sheffield UK

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 04/03/2025 14:43, Roger Mills wrote:

On 03/03/2025 20:13, The Natural Philosopher wrote:

On 03/03/2025 18:17, alan_m wrote:

On 03/03/2025 15:34, The Natural Philosopher wrote:

On 03/03/2025 08:48, Jeff Layman wrote:

A BT rewire has made an extension socket in the kitchen redundant.
I've removed the back box, but am wondering about the best way to
fill the hole before repainting. The hole is about 70 x 70 x 25mm.

I've got enough polyfilla, but it would take several layers
allowing it to dry in between. Or I could partially fill the hole
with mortar and let that dry before using filler. I've even
considered putting the back box in back-to-front and using a thin
layer (2 - 3 mm) of filler over it. Would the thin layer be strong
enough? Could something else like expanded polystyrene be used to
partially fill the hole before using filler?

I have many methods
E.g. (if you have some handy) use a piece of plasterboard wedged in
the hole below the surface of the finished wall and skim. There are
many other  ways to do the wedging.
Simply get ANYTHING that will support the first bodge coat of
plaster - scrunched newspaper newspaper, a blown up balloon, used
condoms, expanding foam, and old bit of expanded foam packaging, or
PU insulating foam.

All it has to do is support the plaster till it sets.
And don't use polyfilla - its way quicker to use several coats of
fast setting plaster.

But often the best material for speed of setting (curing or air
drying) doesn't come in small packs at a reasonable price, especially
if being used for a one off small job.

It comes in small enough packs.

And is cheaper than polyfilla.

Thats why people dont skim walls with polyfilla

https://www.wickes.co.uk/British-Gypsum-Thistle-Multi-Finish-
Plaster---25kg/p/220056

What do you do with the remaining 24.9 Kg?

I dug a bag of O-O-D bonding coat into my back garden to improve
the clay and the drainage. Gypsum seems to be useful for this
problem and unlike Lime is doesn't alter the Ph (AFAIK).

Bonding also contains some sort of granular material which is
also useful for heavy clay soil.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 04/03/2025 15:59, RJH wrote:

On 4 Mar 2025 at 14:43:08 GMT, Roger Mills wrote:

But often the best material for speed of setting (curing or air
drying) doesn't come in small packs at a reasonable price, especially
if being used for a one off small job.

It comes in small enough packs.

And is cheaper than polyfilla.

Thats why people dont skim walls with polyfilla

https://www.wickes.co.uk/British-Gypsum-Thistle-Multi-Finish-
Plaster---25kg/p/220056

What do you do with the remaining 24.9 Kg?

I find it lasts years if wrapped - but it goes off quickly and is only useful for basic filling.

The 10Kg and 5Kg bags of Wickes fine surface filler were more
useful to keep. Unlike gypsum plaster it can be scraped smooth
if it goes off too fast with a stiff steel ruler and then
sanded flat.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 06/03/2025 12:30, Andrew wrote:

On 04/03/2025 15:59, RJH wrote:

On 4 Mar 2025 at 14:43:08 GMT, Roger Mills wrote:

But often the best material for speed of setting (curing or air
drying) doesn't come in small packs at a reasonable price, especially >>>>> if being used for a one off small job.

It comes in small enough packs.

And is cheaper than polyfilla.

Thats why people dont skim walls with polyfilla

https://www.wickes.co.uk/British-Gypsum-Thistle-Multi-Finish-
Plaster---25kg/p/220056

What do you do with the remaining 24.9 Kg?

I find it lasts years if wrapped - but it goes off quickly and is only
useful
for basic filling.

The 10Kg and 5Kg bags of Wickes fine surface filler were more
useful to keep. Unlike gypsum plaster it can be scraped smooth
if it goes off too fast with a stiff steel ruler and then
sanded flat.

This product might be better to keep dry for those small
jobs long after it has expired

https://www.wickes.co.uk/British-Gypsum-Thistle-One-Coat-Plaster---12-5kg/p/141937

And you can buy additives to extend the setting time. Not sure how
much it extends the setting time of a way-O-O-D bag though -

https://www.wickes.co.uk/Extratime-Plaster-Retarder---Pack-of-20/p/168855

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 06/03/2025 12:28, Andrew wrote:

On 04/03/2025 14:43, Roger Mills wrote:

On 03/03/2025 20:13, The Natural Philosopher wrote:

On 03/03/2025 18:17, alan_m wrote:

On 03/03/2025 15:34, The Natural Philosopher wrote:

On 03/03/2025 08:48, Jeff Layman wrote:

A BT rewire has made an extension socket in the kitchen redundant. >>>>>> I've removed the back box, but am wondering about the best way to
fill the hole before repainting. The hole is about 70 x 70 x 25mm. >>>>>>
I've got enough polyfilla, but it would take several layers
allowing it to dry in between. Or I could partially fill the hole
with mortar and let that dry before using filler. I've even
considered putting the back box in back-to-front and using a thin
layer (2 - 3 mm) of filler over it. Would the thin layer be strong >>>>>> enough? Could something else like expanded polystyrene be used to
partially fill the hole before using filler?

I have many methods
E.g. (if you have some handy) use a piece of plasterboard wedged in
the hole below the surface of the finished wall and skim. There are
many other  ways to do the wedging.
Simply get ANYTHING that will support the first bodge coat of
plaster - scrunched newspaper newspaper, a blown up balloon, used
condoms, expanding foam, and old bit of expanded foam packaging, or
PU insulating foam.

All it has to do is support the plaster till it sets.
And don't use polyfilla - its way quicker to use several coats of
fast setting plaster.

But often the best material for speed of setting (curing or air
drying) doesn't come in small packs at a reasonable price,
especially if being used for a one off small job.

It comes in small enough packs.

And is cheaper than polyfilla.

Thats why people dont skim walls with polyfilla

https://www.wickes.co.uk/British-Gypsum-Thistle-Multi-Finish-
Plaster---25kg/p/220056

What do you do with the remaining 24.9 Kg?

I dug a bag of O-O-D bonding coat into my back garden to improve
the clay and the drainage. Gypsum seems to be useful for this
problem and unlike Lime is doesn't alter the Ph (AFAIK).

Bonding also contains some sort of granular material which is
also useful for heavy clay soil.

What he said. I've generally tossed it in the bin as well. Probably a
good thing to add to landfill

--
"A point of view can be a dangerous luxury when substituted for insight
and understanding".

Marshall McLuhan

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Andrew <Andrew97d@btinternet.com> wrote in
news:vqc4ri$2us3r$3@dont-email.me:

And you can buy additives to extend the setting time. Not sure how
much it extends the setting time of a way-O-O-D bag though -

https://www.wickes.co.uk/Extratime-Plaster-Retarder---Pack-of-20/p/1688
55

New to me so thank you.

Wickes do a smaller pack too (5) but disproportionately more expensive at �15.50: https://www.wickes.co.uk/Extratime-Plaster-Retarder---Pack-of-5/p/168853

Amaz not bad at 18quid for 10: https://www.amazon.co.uk/Extratime-Plaster-Retarder-10-
Sachets/dp/B018XQ7HN0

and there will be other sources.

Going rate appears to be around 2quid a sachet.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)