White sand and cement goes dirty looking in rain

[Deane85]

Hi all,

We rendered a new build in white sand and cement - when there is no rain it looks good - then the rain comes and it looks patchy and dirty looking all over. Does anyone know what likely cause is and if it can be easily cleaned or what needs sorting (bit mind boggling given it looks fine when in dry weather)

See attached

 

[Stewie03]

.R.A.F. Mate

 

[Gurva]

Hi all,

We rendered a new build in white sand and cement - when there is no rain it looks good - then the rain comes and it looks patchy and dirty looking all over. Does anyone know what likely cause is and if it can be easily cleaned or what needs sorting (bit mind boggling given it looks fine when in dry weather)

See attached

no waterproofing in the mix