float & set - fixing battens

[Alastairreid]

Applied to wall in 25mm coat. one hit. top to bottom.

far too thick!

Sloppy mix. Like double cream

far too runny!

stick to the bonding plaster which you should find a bit easier.

 

[roughcaster]

I am a newbie to this site and plastering in general and I recently did a complete hallway/stairwell, only ever having done patch repairs before this.

I boxed in the stairwell drop and even boxed in some pipes and electrical conduit.

No-one told me you can't plaster over wood, but even plaster will stick when mixed with enough PVA glue...

However, I have a new problem someone here can help me with: Cement render to a bricked up doorway. I closed it up and the existing wall dressing is cement and plaster topcoat, so I thought I would give it a go.

PVA 50/50 to bare brick - leave to dry. Mix up 5/1 sand/cement. Sloppy mix. Like double cream but not as runny.

Applied to wall in 25mm coat. one hit. top to bottom. some places thicker others thinner. My brickwork not brilliant.

After about 30 minutes the whole lot fell off.

Mixed up new mix and ditto.


Advice needed very quickly 'cos tempers are volatile...
Advice with this job or shall I buy some thistle and go that way?

First of all, never plaster or render onto pva that has dried out. Always work onto it while it is wet or tacky.
A "25mm" coat of cement render, applied in one go, has no chance of staying on a wall. It will slump/split, and fall off, as you now know. It needs at least 2 coats of render,, maybe even 3 for that thickness. As Alastair said,, render/mortar shouldn't be runny. I'd go for bonding coat or hardwall,, that is much easier to build up a thickness of 25mm, but again,, not in one hit. Allow each coat to steady up, scratch it, then put on your next one. Level/rule off when you're out to the desired thickness, float it off, let it set then put on 2 thin coats multi finish.

Roughcaster.

 

[Hipokondriak]

Only just got back on here, at 1800 ish and missed your posts. However, I have had a fairly good day with my wall.

Painted the wall with lots of PVA 60/40 mix.

Whilst wet (ish) mixed up a 4/1&half mix of cement just enough for a half metre section of the doorway.

Started at the bottom and filled to about 10mm. Kept on top of the slumping by taking the "slump" and putting it back on the top of the rendered section, after a while it stoppped "slumping" and has now stuck on.

None has come off yet. Once finger dry, mixed up the next half metre section and filled that in too. I made up a piece of wood with a few nails in it and scratched the surface of the first bit. made vertical wavy lines.

Now on the last top bit, and have about a third of a metre to finish.

It is slow going and is very annoying, but the adage is "slow, but steady, wins the day" isn't it?

 

[roughcaster]

You'll get there in the end that's for sure,,, much practice makes perfect. The only thing i would say about the method you're using,,, it's always better to start coating from the top of a wall,, and work down,,, you'll find it easier to put on as well.

Roughcaster.

 

[Hipokondriak]

Well after a whole day on it, the doorway has got it's first 8mm ish coat of render.

The next coat will be next weekend. If it doesn't fall off before then.

Here are a few pics of the job so far.

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All being well, the other side of the door should be a piece of cake...

Picture 1: lower part of the job
Picture 2: the top bit
Picture 3: thick old plaster coat?
Picture 4: Pastic pipe put in wall to allow cables and such through to other room

I might post an update when I get it all done...

 

[Alastairreid]

well done looks good!

 

[roughcaster]

That really does look good H. Another couple of tips for future reference,,, where the new render/plaster meets the old, get a small bolster/chisel, and chip away an inch or so, of the old plaster/render, to remove any proud, sticking out areas that might spoil the finished look, when the new render joins the old,,,, plus,, better to scratch horizontally rather than vertical. Good job being done there anyway,,, keep us updated,, any probs,, just say.

Roughcaster.

 

[regsmyth]

Oops!

 

[Hipokondriak]

Why the Oops! Have I missed something?

As for the wavy lines, the aerated blocks underneath this have vertical wavy lines, I just followed suit.

Good tip for the plaster edges, though.

Sitting back, now, with beer in hand, waiting for the render to set.

Once this is done, there is a fireplace to the left of this ex-doorway that needs to be "cleaned up" and then a top coat of finishing plaster over the whole wall (about 15ft wide by 7ft6 inches high).

Any tips for this job?

 

[roughcaster]

You enjoy your pint HP,, then when you're ready, just put up a pic of the next job, and we'll have a look,, in the meantime, pass the peanuts.

Roughcaster.

 

[Hipokondriak]

Well it is 10pm and it hasn't fell off the wall yet, so must be a done deal.

I have enough sand/cement to give it another coat in a few days time. I'm going to leave it until Wed/Thur before I tackle that one.

I will attempt to chip out the top coat around the obvious error points and bring the render up to that level, which will give me about 2-3 mm of topcoat to finish.

Here is a picture of the job so far: Sorry it is round the wrong way - but tilt your head and it all becomes clear

Looks good to me...

 

[trowelmonkey1]

try building it up in 2 thinners coats

 

[roughcaster]

I bet you're chuffed with that, you should be. By Wed/Thurs, it will be perfect to work on. Give it a good damp down before you coat it out, because it will have some suction.

Roughcaster.

 

[Hipokondriak]

was that two thinner coats of Render or topcoat/finishing plaster?

 

[Hipokondriak]

I read many posts that refer to suction.

What is it exactly and is best avoided or wanted?

edit 1

Ahh, methinks you are refering to the way the wall "sucks" the moisture out of the applied coat, then it falls off 'cos it is too dry?

edit 2

The clarity of thought brought on by BEER