Patch concrete ceiling

[Topandtail]

Hi, a chunk of concrete has fallen off my Mums outhouse porch ceiling. The hole is about 40mm at the deepest point.
How do I go about preparing this for render?
Do I need to put something on the rusty rebar and will a bonding agent be required?
Also can I build up render in successive coats to that thickness or will it just come crashing down at a later date?

Thanks,
Peter

 

[Danny]

Welcome.... that looks like it is getting very wet....

Where abouts in the old are you?

Sent from my SM-G900F using Tapatalk

 

[Topandtail]

I'm in Newcastle. The house was built in the 1930s and I think over the years the rainwater has made its way through the concrete causing the rebar to rust.

 

[Pug]

There's a product I used years back called bellzona (I think) like a lightweight putty. Stuck like shite to a blanket.

 

[Pug]

http://www.belzona.co.uk/en/products/4000/4141.aspx

 

[Topandtail]

Nice one Pug, looks just the job!
Will post a pic when it's done