How do you fill a trench hole?

[John2016]

I recently had my wall skimmed with plaster with a excellent finish. But, I later noticed I needed to install a light switch at a new location. I had to break away the plaster to install a new conduit.

The trench is roughly 35mm deep and 20mm wide, I was going to glue the conduit with some Gripfill and then attempt to plaster or fill over it working in layers.

In the end I want the finish to be as smooth and level to the walls. I'm happy to spend time sanding if needs be.

Can anyone provide any recommendation on products to use?

Thanks.

 

[rochester plasterer]

Thistle bonding plaster to fill it in. Then easy fill over the top and sand.

 

[John2016]

How would you recommend mixing it?

Would I need to build it up in layers?

 

[rochester plasterer]

Mix the bonding plaster up quite thick. Not to thick you can't scoop it out the bucket. And if it's to runny it will not bond and sag and fall out before it has the chance to set. If you haven't used it before mix a small amount and gob a bit in the channel first to build it out. Wait a half hour or so and let that pull in and gob the rest in to fill it complete. Ideally you need to leave about 2-3mm back from the existing wall so when you put the filler on top it fills flush with the wall. Otherwise you will end up with a beer belly in the wall Send Pics as you go be good to hear how you got on

 

[John2016]

Many thanks,

Will send pics, I was thinking should I attempt to PVA the wall inside the trench before applying bonding or/and use blue grit paint as a key surface?

The previous plaster place a mesh netting on the wall which I will add before I use Gyproc Easi-Filler?

 

[rochester plasterer]

Just wet the channel with water to kill the suction. You can add some mesh over the bonding after but you don't really need to. It's not like a joint in plasterboard that needs meshing (scrim) it wont crack if filled correctly.

 

[vinn]

What is the "mesh" thats been exposed and cut through? Has the wall been tanked with damp proofing mesh? Why did the previous plasterer use the mesh?

 

[John2016]

What is the "mesh" thats been exposed and cut through? Has the wall been tanked with damp proofing mesh? Why did the previous plasterer use the mesh?

The plaster recommended mesh as it would reduce the chances of it cracking as we were skimming the wall over previous plaster. The base surface (old plaster) was painted over with 'key' green paint.

 

[rochester plasterer]

That mesh looks like the mesh plasterers use on outsides for rendering. The key green paint you say he used is probably blue grit or thistle bond it. It's basically pva mixed with grit so the plaster has a good key. There's still no need to mesh the area you need to fill John just fill it in