Hair-line cracks in external render

Habbakuk

I've got some almost hair-line cracks in the external render to the house. It's a sand and cement render but this guy said to me that ther might be lime in it as it's not that hard. Anyway, it's allowed dampness into the house in one location. Rather than re-rendering the whole front of the house, I'm hoping to scrape out the hair-line cracks a little just enough to fill in with something that will prevent the water from penetrating; hopefully something that will expand. Otherwise, it will cost me a couple thouand at least to have it re-rendered. My question is, is this feasible and what substance should I use to re-fill the cracks? Thank you.

Ianwzzz

I use this http://www.sandtex.co.uk/products/sandtex-ready-mixed-masonry-filler/

Open the crack up fill and paint. If water has got behind and render has blown you will have to remove it and re render.

Habbakuk

OK thank you. It doesn't look like the render has blown at all.

Habbakuk

I wwent down to the local builder's merchants and they didn't have Sandtex but gave me Everflex 125 One Hour Caulk. Says it's flexible and for sealing and filling gaps and cracks both internally and externally? Anybody know if this stuff is any good?

Also, once I scrape out the hair-line cracks, will it be fine to wash the wall and the cracks with a pressure washer? I would be a bit concerned about getting water into behind the existing render and then sealing over.......Thanks.