Wall chasing and replastering - any tips?

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Tim S

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Nov 16, 2008, 5:13:55 PM11/16/08
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Hi all,

the time draws nearer to when I'll have to chase out all the walls for new
electrics.

Got the ALDI chaser and a funny cranked chisel bit for my SDS.

But, I've been thinking - how hard will it be for an eejit like me to
plaster in the chases afterwards? And what should I use? Bonding, then a
skim coat - or browning, or a mixture of Bonding and finishing plaster
(IIRC) laid in one go (heard somewhere that someone swears by this for
patching up).

Is it best to cut the chases tight to the oval conduit, or leave a gap for
the plaster to get round the sides (better grip?)?

The walls appear sound and the final finish will probably be a lightly
textured paper painted with emulsion (no, not woodchip!).

A mate was recommending re-skimming the lot, but it seems a waste and a lot
of work if the rest of the plaster is good. Granted, you could paint a
re-plastered wall directly and it would look good, as he has (Hello Mark!)

Cheers

Tim

Andrew Gabriel

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Nov 16, 2008, 6:05:36 PM11/16/08
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In article <49209b23$0$501$5a6a...@news.aaisp.net.uk>,

Tim S <t...@dionic.net> writes:
> Hi all,
>
> the time draws nearer to when I'll have to chase out all the walls for new
> electrics.
>
> Got the ALDI chaser and a funny cranked chisel bit for my SDS.
>
> But, I've been thinking - how hard will it be for an eejit like me to
> plaster in the chases afterwards? And what should I use? Bonding, then a
> skim coat - or browning, or a mixture of Bonding and finishing plaster
> (IIRC) laid in one go (heard somewhere that someone swears by this for
> patching up).

Bonding won't polish up nicely as it's got large particles in
it (looks like mica and other stuff).

Liberally paint the cut edges and the exposed plastic trunking
with dilute PVA to seal the edges, and make the plaster stick to
the PVA. Try to avoid it getting into the accessory boxes or
down the trunking (it will permanently stick PVC to the inside
of the trunking).

I use just finish coat, and if possible an old bag past its date,
as that means it will set quickly (you don't want to be waiting
2 hours to finish polishing off the surface of the chases).
I do two coats -- the first is bonding made from the finish coat
plaster (mix in a little PVA), which saves lugging a separate bag
of bonding coat around. Bring that up to 1-2mm below finished
surface. It will crack (being too thick for a finish coat), but
that doesn't matter. Then use finish coat (no PVA) to do level it
off. Apply the finish coat whilst the bonding coat is still damp
(but set, or very nearly so).

> Is it best to cut the chases tight to the oval conduit, or leave a gap for
> the plaster to get round the sides (better grip?)?

Cut to exactly the conduit size. Chasers normally come with
spacers which give you exactly the right size. Cut the chase
freehand following a pencil line -- the inevitable slight curve
you'll get holds the oval trunking in place without any nails
needed. First time, I cut against a straight edge and got a
perfectly straight chase, which meant the trunking just fell
out of it;-)

> The walls appear sound and the final finish will probably be a lightly
> textured paper painted with emulsion (no, not woodchip!).
>
> A mate was recommending re-skimming the lot, but it seems a waste and a lot
> of work if the rest of the plaster is good. Granted, you could paint a
> re-plastered wall directly and it would look good, as he has (Hello Mark!)

If it's a small piece of wall, and you're good at skimming,
and the wall isn't perfect, then I would reskim. Otherwise,
it's not necessary. If you're not good at plaster finishing,
you would be advised to allow for sanding the chase down
afterwards. They do have to be perfect to be invisible on a
painted wall, and your eye is easily drawn to the tiniest
imperfection of that sort.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

BigWallop

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Nov 16, 2008, 6:25:42 PM11/16/08
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"Tim S" <t...@dionic.net> wrote in message
news:49209b23$0$501$5a6a...@news.aaisp.net.uk...

The point is to get a good adhesion to the brickwork and the existing
plaster, so anything that will let this happen is a good thing. I've heard
of a stretchy tape that will bond to the brick surface and grab the plaster
to it. It is something like the plaster bandages they use for setting
broken bones I think. Apply dry and wet and press into the channels to get
it stuck.

Plaster is normally built up with a coat of bonding and a coat of finishing,
so if you can copy that in any wider chases, then great. But it might be
better and cheaper to stick with just finishing plaster throughout the job.

The making of a smooth finish is in the soaking and polishing. After
applying the plaster, leave it for an hour and then soak the surface of it
thoroughly with a paint brush. Slide your plastering float firmly over the
surface to make it smoother. Do this a few times until you are happy that
it's level with the original surface, and is as smooth as a babies
whatsitmabob.

Remove any wallpaper before plastering as well, or your new plaster will be
level with the paper instead of the original plaster surface.

I bet you get the knack of it in no time at all.

Tim S

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Nov 16, 2008, 6:42:34 PM11/16/08
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Andrew Gabriel coughed up some electrons that declared:


Thanks Andrew. Looks like I'd better plaster up after 1st fix and get any
required sanding out of the way as it's as messy as chasing...

I know it's hard to get a good patchup on a wall to be painted with
emulsion - that's why I'd resigned myself to hanging paper, either lining
or textured, then painting. Fortunately my paper hanging skillz are OK,
except on ceilings.

I'll certainly employ the PVA. With any luck if I sink the backboxes with
care, I might avoid much pastering around them.

For protecting the accessory boxes, I was going to poke the conduit through
the knockout, then add a blob of sealant to bung the hole up, and cut out a
few bits of plastic sheet (like 3-4mm thick stock) to stick in the front.
Probably only need 4-5 as these will be resuable.

Cheers

Tim

Andrew Gabriel

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Nov 16, 2008, 8:05:53 PM11/16/08
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In article <4920afea$0$499$5a6a...@news.aaisp.net.uk>,

Tim S <t...@dionic.net> writes:
> For protecting the accessory boxes, I was going to poke the conduit through
> the knockout, then add a blob of sealant to bung the hole up, and cut out a

You'll probably find the knockouts are deeper than the conduit,
except in the case of very shallow boxes. You can make the
channels deeper as they approach the box, although you might not
want to make them that deep everywhere.

> few bits of plastic sheet (like 3-4mm thick stock) to stick in the front.
> Probably only need 4-5 as these will be resuable.

The trick I mentioned in the other thread about plastering over
back boxes is actually what I do with all back boxes when I'm
skimming (with the wires tucked in behind). I get a much nicer
finish if I'm not worrying abour stearing the trowel past wires
and avoiding filling backboxes with plaster. I then cut out the
plaster and the card when it's half set (except those boxes I'm
leaving plastered over). It's often occurred to me that someone
should make a piece of semi-flexible plastic for this purpose.

BigWallop

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Nov 16, 2008, 8:08:53 PM11/16/08
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"Tim S" <t...@dionic.net> wrote in message
news:4920afea$0$499$5a6a...@news.aaisp.net.uk...

Pack the boxes with old newspaper. You can throw it away after you're
finished. But it stops you filling the boxes with plaster.


Message has been deleted

Tim S

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Nov 17, 2008, 6:23:05 AM11/17/08
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m...@privacy.net coughed up some electrons that declared:

> On 17 Nov,


> and...@cucumber.demon.co.uk (Andrew Gabriel) wrote:
>
>> The trick I mentioned in the other thread about plastering over
>> back boxes is actually what I do with all back boxes when I'm
>> skimming (with the wires tucked in behind). I get a much nicer
>> finish if I'm not worrying abour stearing the trowel past wires
>> and avoiding filling backboxes with plaster. I then cut out the
>> plaster and the card when it's half set (except those boxes I'm
>> leaving plastered over). It's often occurred to me that someone
>> should make a piece of semi-flexible plastic for this purpose.
>

> I'm sure I've seen them somewhere.
>

You're not thinking of Yoozy boxes are you? These are similar in concept but
are used when plastering is done after 2nd fix (they are effectively a
spacer that holds the plate out from the wall and fills the gap to stop the
plaster getting in. Doesn't help the plasterer, except in as much as the
electrician won't go and kill him for filling his boxes with muck.


Cheers

Tim

Andrew Gabriel

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Nov 17, 2008, 6:46:00 AM11/17/08
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In article <49215419$0$498$5a6a...@news.aaisp.net.uk>,

Tim S <t...@dionic.net> writes:
> m...@privacy.net coughed up some electrons that declared:
>
>> On 17 Nov,
>> and...@cucumber.demon.co.uk (Andrew Gabriel) wrote:
>>
>>> The trick I mentioned in the other thread about plastering over
>>> back boxes is actually what I do with all back boxes when I'm
>>> skimming (with the wires tucked in behind). I get a much nicer
>>> finish if I'm not worrying abour stearing the trowel past wires
>>> and avoiding filling backboxes with plaster. I then cut out the
>>> plaster and the card when it's half set (except those boxes I'm
>>> leaving plastered over). It's often occurred to me that someone
>>> should make a piece of semi-flexible plastic for this purpose.
>>
>> I'm sure I've seen them somewhere.
>>
>
> You're not thinking of Yoozy boxes are you? These are similar in concept but

I don't think so, but their website is so bad, I can't actually
see what the product is. The pictures demonstrating it all show
a installation where the cable doesn't run in a line from the
accessory box too, which is not good ;-).

> are used when plastering is done after 2nd fix (they are effectively a
> spacer that holds the plate out from the wall and fills the gap to stop the
> plaster getting in. Doesn't help the plasterer, except in as much as the
> electrician won't go and kill him for filling his boxes with muck.

I remove all the accessories, and coil the wires up so they are
hidden in the back box and not sticking out. May temporarily
connect with chocolate block connectors or leave the circuit
turned off, depending. If you're going to the lengths of
replastering, you're usually at least replacing the accessory
plate items with new ones too. (Keep new ones away from damp
plaster -- it can stain some finishes.)

ARWadsworth

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Nov 18, 2008, 3:45:59 PM11/18/08
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<m...@privacy.net> wrote in message news:4FFF9A257C%brian...@lycos.co.uk...

> On 17 Nov,
> and...@cucumber.demon.co.uk (Andrew Gabriel) wrote:
>
> > The trick I mentioned in the other thread about plastering over
> > back boxes is actually what I do with all back boxes when I'm
> > skimming (with the wires tucked in behind). I get a much nicer
> > finish if I'm not worrying abour stearing the trowel past wires
> > and avoiding filling backboxes with plaster. I then cut out the
> > plaster and the card when it's half set (except those boxes I'm
> > leaving plastered over). It's often occurred to me that someone
> > should make a piece of semi-flexible plastic for this purpose.
>
> I'm sure I've seen them somewhere.

Maplins used to sell something like this. They stopped selling it years ago
(at least 10)

Adam


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