Andrew Gabriel coughed up some electrons that declared:

In article ,
Tim S 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.



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