Extensive render repair - waterproofing required?

I asked for help some time regarding repairing some damage to my render. The response I got here worked perfectly. I used sharp sand for the mix and after scrubbing down the texture perfectly matched the original 1930's render. Other repairs (which had started to crack) use builders sand and you could clearly see the mismatch from a distance.

I'm now in the process of removing render around around several metres worth of cracks. I'm planning to rerender as per the original repair but was wondering whether I should be using some waterproofing agent. Can anyone give me some advice?

Also under a few of the cracked areas the brickwork is loose. What should I be doing here by way of repair?[/url]

yes you must repair the brickwork first before rendering.i always use waterproofer as you need a additive anyway.there are many reasons for cracks.maybe your laying to thin.maybe it could be the sun dried it to fast.perhaps if you put pva/water on the background area first this helps or at the least water. simon the spread/builder