Filling plaster walls

Hi all,
I've just had some electrical works done (house re-wire) and I'm left with floor to ceiling channels about 30 mm deep and maybe 100 - 120 mm wide from where they chased in the wiring to the new switchboard. The cables are held to the brickwork with cable clips. The walls in question are brick with cement/plaster finish. No laths or fibrous plaster in evidence.

Whats the best thing to use to fill?
I initially thought a dryish cement mix with a finishing surface of plaster or polyfilla, then I thought mixing my own plaster like powdered poly-filla or some such thing and doing the whole job with that.

Is there a standard product to use?
I'm most concerned about the stuff slumping out of the channel and ending up in a big pile on the floor before it sets. I guess 2 or 3 stages of working up to full depth over time would solve this.

Any suggestions for the right approach?

Second question - I have a similar width/depth channel outside in the external wall above the meter itself. This wall is also solid brick/render with a "smooth-but-bumpy" surface (if that makes sense....its not flat, not rough, smooth to touch with bumps.....) What's the method to achieve this type of finish - it's very common on the houses around here all circa 1930. The modern rough render stuff that is trowelled on is too sharp when it dries - I want to smooth out the spikey surface but leave the "bumps"

Again, suggestions most welcome.

Cheers,
Geoff

don't know if you can get it here ( can't see why not ) but in uk when I (legally) chased into my plaster to put in two way switching in a couple of places I bought bags of patching plaster to fill in the channels. Filled it in in stages slightly proud and then sanded. ( helpful hint if it is runs down the channel you've got it too runny!! ) It helps of course that we usually wallpaper over the top but you should get a reasonable result provided that you don't use gloss paint on top of it. I put protective channel over the cables before I plastered but this wasn't a legal requirement.

Back in the 80s the big fashion was to render your internal walls with a product called artex and then make patterns in it either with a stippling roller ( a foam roller like a paint roller with lots of little bumps on it ) or swirls using a variety of implements like combs. I often think that the person who bought my house must have had great fun removing it when the fashion changed. Ceilings were done like this too ( hides a multitude of sins ). I would suggest that if you only have a small area of render to do then maybe a stippling roller would give you the bumpy finish you desire ( its not how they do it when they do the whole house I think). With the artexing I practised my patterns on a board first ... you could always try on a bit of scrap sheet and see if you can get the desired effect. had cavity wall insulation put in my house ( which requires 4" diameter holes to be drilled at intervals all over the outside of the house ) and as the house had a "tyrolean render" (bumpy render to you and me ) finish it had to be patched over all the holes. they weren't able to match the bumps exactly ( and these guys did this as their day job ) but it was close enough for folk music and if you're planning on painting the exterior walls anyway it won't be noticeable. If you only paint the patches matching the colour is going to be a b***h.

hope this helps

Jackie

Hi Geoff,

It was a while ago now but I had a similar problem with my parents house, Basically I glued a small section of Gyprock in place to cover the cavity then rendered it flush with the wall.
I can't say that it's the correct method but it hasn't moved to date and if I or my parents need to get at the conduit underneath it's a lot simpler.

regards,

Himzo.

Hi

Quote:

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Is there a standard product to use?
I'm most concerned about the stuff slumping out of the channel and ending up in a big pile on the floor before it sets. I guess 2 or 3 stages of working up to full depth over time would solve this.

---

Use Plaster! See if you can buy a bag or two of premixed sand cement plaster mix. If not you could buy a bag of plaster and plasterers sand, and mix it yourself (one bag of plaster goes a long way though, considering what you need:-) ).

Mix the 3 or 4 of sand to 1 of cement or the premixed bag to a "doughy" consitency, wet the area of the wall to where you want to apply the plaster (wetting the wall helps prevent the plaster from drying out too quickly and then not adhereing properly.). Apply the plaster firmly into the chased channel in an upward motion. A plasterers float (rectangular trowel) makes the job easier. I presume that you have a set plaster wall (originally a white plaster finish). This will make it a bit difficult to use the float (trowel) to obtain a slightly recessed finish to allow for a new set plaster finish.

I guess it does not really matter what you use to insert the plaster into the channel as long as you fill it to a level just below the current surface - about 3mm below) then you could use the jointing cement (not the glue of course)used for gyprock installations, as the surface plaster finish.

I expect that you will ultimately have hairline cracks appear at the edges of the filled channel - in the surface fininsh. Perhaps you could use the gyprock jionting tape to minimise this cracking. Contact your local gyprock store and ask them.

In any case you need to finish the application leaving a slight rise in the centre so that you can sand it flush after is dries and shrinks a little.

HTH

Geoff
Im in Malvern and would be glad to give you a quote if you are not comfortable doing the work, u can call me on 0413188881

Thanks to everyone - I have lots to go on now...

And to Guy - I may well give you a call seeing you are close by as well.

Cheers,
Geoff.

I wouldn't try just filling the void with any sort of filler alone.

probably the best option is to fill the groove as cleanly and as level as you posibly can with plaster board.

how well you fix it will determine how good the job ends up.

cutting back the plaster so you can fix to the brick work would probably be the best. fix using cornice cement & possibly some mechanical fasteners (screws & plugs)

flush it up as best you can then set the joints like any other.

but filling the gap as securely and as flush as you can beforehand would be the go.

cheers