Flattening a really complex surface?

[loply]

Hi folks,

I skimmed a chimney breast last night with two coats of multi-finish.

I struggled like hell as the shape was all over the place - where the old fire was it had been boarded over and was 5mm shy, the whole thing was convex, the bottom curved in a bit and there was a 'rim' all around the old chimney which stuck out plus a few other 'ridges' here and there!

I stuck the first layer on quite thick but it was an absolute bugger to get flat and I had undulations and dips for ages.

First coat went off before I got it fully sorted so I had to use the second coat to help too.

Got there in the end (more or less) but I wonder if I could have used a darby to help? Or does this just not work on plaster?

Thanks,
Rich

 

[roy c]

Maybe you should of "dubbed" it out with Bonding first then skimmed it...

 

[roughcaster]

Agree 100% with Roy. Multi finish is not meant for building out hollows and bumps. Bonding Coat is what you should have used, but after prepping/PVA etc.
Another thing, you should always hack/cut back any "ridges, sticking out bits, proud edges" or anything else that might cause you to build up a thicker coat than necessary, don't try to build the plaster out to the thickness of these ridges and bumps, hack them back carefully with a scutch hammer, bolster, chisel or any other tool,, makes things a lot easier in the long run.

 

[loply]

Thanks for the advice folks, will bear that in mind for future jobs.

What about my idea of using a darby to flatten it, would that have worked if I'd whacked on a thick layer of bonding? Or would it be too hard to move it around?

Cheers,
Rich

 

[roughcaster]

A darby would "not" have helped you one bit in that situation Rich. This is really a "skim coat" onto an uneven wall. Even though you have thin bits here, and deeper bits there, a darby would be of no use. You're having trouble with the un-even surface using a trowel, 11", 13", whatever, but if you put a darby or a straight edge across the uneven wall/chimney brest, god knows how thick it might need to be. The best thing you could have done, would be to cut back the much of the plaster on the chimney brest, fit 2 Expamet thick/deep coat corner beads on the corners, plumb them up both ways, making sure the beads are set for an even coat all across the c/brest/return corners, let them set, then plaster the whole c/brestst wall/s out to the thickness required. As I said, you would need to remove most of the old plaster if you were to put on beads and a proper float coat. You CAN use a straight edge or a darby doing it that way. Much more work involved doing it that way, but you'll get/ should get, a great result.

 

[loply]

Thanks for the advice, will bear all this in mind for future.

On reflection it may have been quite easy to re-board it over the top with screws + plugs and some adhesive too. That would sure have flattened it out and been quite quick to do presumably.

 

[Micilin]

Thanks for the advice, will bear all this in mind for future.

On reflection it may have been quite easy to re-board it over the top with screws + plugs and some adhesive too. That would sure have flattened it out and been quite quick to do presumably.

It's all about reflection!

Nailable plugs the best option for that, IMO.