Process involved in roughcasting over existing roughcast?

[rob110]

Hi

I want have a go at roughcasting my old garage, it is currently roughcast and I would like to (thinking it is easier) to roughcast over the existing, there is a small section about 2 foot sq which is hollow, the remainder of it seems pretty sound but.

I have done a bit of plastering and whilst I know it wont be to professional standards I am happy to have a go.

Question is:

Can you roughcast over existing roughcast and generally speaking what is the process to be followed in this case.

Cheers

Glasgow!

 

[maaaaaaaaat]

yes you can render over the old if its sound,and fairly fine.but in my experience,to achieve a decent finish it must be stripped back,to either brick or original base coat. check my gallery.

 

[rob110]

Thanks for reply

When you say render, do you mean to put my sand cement mix over existing and then pebbledash it and job done?

 

[maaaaaaaaat]

Thanks for reply

When you say render, do you mean to put my sand cement mix over existing and then pebbledash it and job done?

yeah,thats just for starters.firstly,wash down with hose pipe,apply weak mix sbr,let set and youre ready to go.now the job starts,ask yourself,why dont all plasterers do pebbledashing,why do dashers get good money,you cant repair **** ups,not like spreadin.,now lash the muck on and start throwing stones.

 

[Alastairreid]

Thanks for reply

When you say render, do you mean to put my sand cement mix over existing and then pebbledash it and job done?

pressure wash the existing roughcast, apply sbr slurry and let dry,fit corner, bellcast beads and stop beads around windows and doors, scratch coat with a mix of 5/1 sand cement put waterproofer in the mix, then 4/1 sand cement plasticiser 2nd coat and hit................ stand back and admire your handy work

or........you can google powerwall or MR polymers. good luck.

 

[rob110]

Alastair - cheers

Fix the beads with some mix? What size beads?

Scratch coat to what thickness? Full depth of the bead or leave some of the bead for the 4/1 coat.

Should I knock out the old bellcast first it is out quite far?

 

[Alastairreid]

Alastair - cheers

Fix the beads with some mix? What size beads?

Scratch coat to what thickness? Full depth of the bead or leave some of the bead for the 4/1 coat.

Should I knock out the old bellcast first it is out quite far?

13mm beads

scratchcoat approx 8mm

yes hack off the old bellcast.

2nd coat flush with the bead then cast away.

 

[rob110]

Any blown bits of rough cast, hack out till i find a secure bit, then level this with some mix to existing roughcast level, let it dry, then sratch coat it?

What is the best tool for scratching with? Should scratches be vertical only?

Lastly, What is a safe area for a novice to work over at a time, foot to head height? 2 or 3m wide?

Thanks again for your help

 

[roy c]

If you don't know how to scratch then I wouldn't attempt the job!!!! Even for a novice you must have a basic idea of rendering......to do what you intend to do>.