Internal render advice needed

[BarkingMad]

Hey all,

Need a bi of advice about rendering inside.

DPC has been installed a few months ago, plaster removed from bottom 1 metre of wall and ready to go.

Ive bettened the wall along the bottom with a 19mm deep batten (existing plasterwork is 19mm deep too so can use a straight edge to get it all a bit more level once on).

So, I'm supposed to re-plaster this wall with 3:1 sand / cement mix with added waterproofer and salt retarder. Mixed up a small load today to test it. What a load of rubbish it was. I used sharp sand - it was ful of gravel! Is it supposed to be like this! It was almost ballast rather than sand!

I tried spreading the stuff on the wall and it just wouldn't take at all. Tried wetting the wall down too - didn't help. It just sort of dragged round the wall and then fell off! Any idea what I'm doing wrong?

I've heard talk fo washed sharp sand - what's this? Is there any other sand I can use instead?

I also heard about Thistle DryCoat. Anyone used this? What's it like? Does it mix like Bonding and is it as easy to spread as Bonding? Any idea where sells it? Any of the sheds?

Thanks in advance.

 

[JerryM]

Barkingmad,

u've got me chucking for sure.

don't use sharp sand - u must use plastering sand (ie washed sand). the reason for this is that normal sand contains salts whereas the plastering sand doesn’t. these salts will otherwise lead to damp.

i use 3:1 on the 1st coat (10mm) and 4:1 on the 2nd coat (8mm). the mix is crucial - it must be soft but not sloppy - try a little batch to start with to get the feel for it.

Don’t wet the walls. do add the waterproofer and the salt retarder (i don't but i guess depends on the dpc)

there is a sort of trick to putting it on. start at top and push up into existing plaster. Then work downwards applying as “layers” on top of previous “layer” - it's like your putting wedges on top of each other trowelling upwards all the time. lightly strake when it’s starting to set for a key.

2nd coat is applied the same. make sure it's starting to set before applying otherwise it will bag (sag). u will need a darby to plumb the walls in 1st vertically then horizontally.

then lightly strake for a key for the finish plaster. gauge the coat thickness to leave 3mm for the finish to come level with the existing plaster.

NB an air gap must exist between the floor and the plaster/render typ 25mm. i produce this at the end when the render is almost set by pulling a trowel along the wall at an angle.

i don't know anything about the drycoat.