To seal or not to seal? - Should i seal my patio?

[Mrs Grumpy]

Hi

I have a paving all round the house which I have pressure washed twice now - it takes around 3 days altogether. It should be sandstone coloured but within a year it is as black and lichen covered as it was before I pressure washed it. I can't work out why it gets so bad as we live in the country.

Would sealing stop it going black again? I don't want to change the colour and I don't want a shiny surface so I'm guessing if I do seal it it will be with an impregnator.

But my question is - is there any point in sealing it? Or will all the crud just build up again anyway.

Any advice would be greatly appreciated. They are riven slabs but not natural stone. I also have a new patio onone side which is natural sandstone - could I/should I seal that too? It's not a year old yet and quite green already.

Thanks in advance

[KLS]

Is the paving often shaded by trees or something else overhanging it?

[Mrs Grumpy]

Thanks for replying.

As it runs all round the house, there are parts shaded by trees, Ironically the area that get blackest is on the south side in full sun most of the day?! So much for sun bleaching effects!

[Tony McC]

Sealing may help, but that then becomes an annual or bi-annual task, and an expensive one at that, as a good sealant isn't cheap.

I've been playing around with an anti-algal treatment, Wet'n'Forget, which is proving to be bloody impressive. No return of the algae, no return of the lichen, no visual effect on the various substrates, and it's costing less than 2p/m² to treat paving.