Rotten Plaster and What's Next for a Complete Novice...

[WickedDNA]

Hi all!
Firstly, if this post is in the wrong place, please move it to the appropriate thread, thanks.

Recently, I tried to erect a new bathroom cabinet.
Given the size of my bathroom, there's only one place to put it, which because of tiling, is already quite high.
It's an outside wall with plaster on the inside, then concrete, then brick.
Drilling is very difficult.
The plaster came away and crumbled quite easily and I'm left with a couple of large holes in the plaster which I can easily fill BUT that plaster I fill it with will also be the site of the new holes.

...aaaaand finally, the question.
What's the best way to right the plaster, site the new holes, all so it doesn't fall down?
(Do I need to make a bigger hole? Can I site some wood behind the plaster to distribute the weight of the cabinet?)

I'm not very good at DIY.
If the advice is for a drunk six year old, I'm okay with this.
Thanks for reading!

 

[He who knows]

It's an outside wall with plaster on the inside, then concrete, then brick.

Actually that looks like plasterboard, fixed to the wall with "dots and dabs" of adhesive, hence the small void behind it.

You can't fix anything to it - you absolutely have to drill through into the wall behind and use the appropriate wall plugs.

Drilling is very difficult.

You need to make it easier, then. If the problem is that you don't have a good enough drill, then get one. If your masonry bits are knackered, buy new ones. (They are expendable - don't assume they'll have a long life if you are drilling into cement and hard brick).

If you are going to buy a more powerful drill then go for one that will also be able to tackle anything you might want to throw at it in the future, rather than just drill small holes in brick, and when you do, you'll discover that a good one, with good quality bits will drill into your walls with contemptuous ease.

Go for corded, not battery.

SDS+ or SDS Max.

4 Joules or more.

Make sure it has rotostop (chisel setting) and a clutch.

Any good "pro" make - Makita, Hilti, Blue Bosch....

Look on eBay for used ones, they're well made and robust, so even if they look a bit scuffed and dirty they should be fine, and spares tend to be available for years. For the cost of a new DIY-type make like Black&Decker you should get quite a good, or quite a long way towards a good, used one.

The plaster came away and crumbled quite easily and I'm left with a couple of large holes in the plaster which I can easily fill BUT that plaster I fill it with will also be the site of the new holes.

Yes, but the holes you are fixing into, the holes with the wall plugs taking the load, will be in the solid wall behind the plasterboard.

...aaaaand finally, the question.
What's the best way to right the plaster, site the new holes, all so it doesn't fall down?

It won't fall down if the screws go into the solid wall behind the plasterboard. Either use long plugs so that there's a decent amount in the wall or take a second plug (reversed), or an old drill bit (shank first), or a bolt or machine screw, or a thin dowel, and use it as a drift to knock the plug fully in.

You could square off the edges of the hole and make plasterboard patches, but as there will be a cupboard over it you don't have to obsess over an invisible repair. Filler should do.

(Do I need to make a bigger hole?

No - repair the hole in the plasterboard, and drill through into the solid wall behind it to put the wallplugs for the screws holding the cabinet up.

Can I site some wood behind the plaster to distribute the weight of the cabinet?)

Shouldn't be necessary - just drill through into the solid wall behind it to put the wallplugs for the screws holding the cabinet up.

 

[WickedDNA]

That's a thorough response.
I thank you for the time you've spent on it.