Wall chases

[Pete83]

Hi
Im doing the wall chases before I get an electrician to rewire a 3 bed bungalow and wanted some advice please. I was planning on using 25mm oval conduit as per the picture but the wall chaser only goes up to 30mm so it’s quite a snug fit, is this sufficient for the plasterer to fix it in place as there’s not enough room for the conduit to be pinned to the wall unless I use grip fill? Also I have some breeze block walls which I’m assuming I can replace the metal capping already there rather than having to chase into the wall?

Many thanks

 

[JohnD]

it looks too shallow to me. I've seen plaster crack when so thin.

apart from gripfill, I've used cable clips (16mm T&E size IIRC) to temporarily hold oval conduit tight to the wall when plastering, leaving a slight gap round the clip, which can be pulled out and made good once the plaster has set and holds the conduit in place.

It's regional practice here to use S&C as a backing coat, which is stronger but slower to harden.

Plaster and mortar stick to galvanised capping better than to PVC, so less likely to crack.

 

[Pete83]

Thanks John, I’ll cut the chases deeper, appreciate the help

 

[sparkwright]

it would be better if you fixed the conduit back with galvanised clout nails, either side of the tube, and plastered over all of this.

By clipping the conduit, and removing the clips as you plaster, is not a great idea as you risk the plaster cracking in the future. The nails will keep it in place forever.

 

[Pete83]

Thanks, hopefully there’ll be enough room to get some nails down the side of that

 

[Harry Bloomfield]

As above, it needs to be deeper. If you need more width, can you not run chaser down twice? Trying to plaster over a surface, which continually moves, will be impossible. The odd time I have needed to do it, I have used 35mm galv clout nails with large heads, into the mortar joints at a skew angle, so just the head traps the side of the tube.

 

[Pete83]

Thanks for the comments, all makes sense

 

[crystal ball]

Or do away with the conduit & clip the cables

 

[Sureitsoff?]

hot glue works as well to hold conduit/cables to the wall

 

[opps]

The house I am currently working had very shallow chases. They were set back by about 5mm. The electrician used solvent based Gripfill but didn't PVA the chases first. Gripfill does not stick to dusty brick work. I ended up having to PVA them and then use 2 pack filler to lock them in place (to eliminate any bounce). I then filled them with Toupret TX100. Then sanded, filled, sanded and filled and sanded again. When shining a light over the surface I could not see the chase. That said, I do expect then to bulge up slightly in 5 years or so.

When doing my own chases, as above, I often use my hot melt glue gun to lock them off. Unlike gripfill, it sets in seconds