We have a highly shaded area for a flagstone patio, recently renovated to be relayed, level, etc. What would be the recommended ratio of bleach to water to mix to be successful? Don't want to pressure wash as many of the stones used are original. Tried vinegar and water mix for moss; unsuccessful.

What are your flagstones made of? What are you are trying to clean off of your flagstones? If you have a softer limestone that is greying or mossy, you could try a product called Bio Wash....

One cup of bleach in a gallon of water is a good mix. Clean after a good rain, or wet down the stones and surrounding area first. Apply the mix with a tank sprayer, avoiding overspray.
Scrub with a car washing brush after about ten minutes, then rinse. This works wonders on many types of stone. I personally don't recommend sealing exterior stone.

Hose and a broom. Wire brush for the worst of it.

Muriatic acid, vinegar and bleach...can cause harm to the plants and animals in your lawn and garden.

It has been my experience that a broom and a garden hose is all you should need, in most cases. If you must resort to the big guns then you should use a wire-brush. You can get a wire brush on a pole, like on a broom handle. No damage to the stone. No damage to the living things in your lawn or garden.

I've used the wire brush on occassions when we were dealing with really old flagstone, where it gets a film of algae on the surface. Careful power washing can also do the trick, but have a wire-brush on hand as well.

best of luck :)

Our flagstone is stained with exudation from aspen trees. What would do the best job to clean this off? It is dark.

First try a scrub brush plus elbow grease....if it's dark and really on
there good, and especially if it's a large area, then you'll probably want to move up to a power washer.

The information provided above is great. I did not see anyone mention rust and paint spots on flagstone (Shalic Sandstone). I purchased a home with flagstone landing. The railings drilled though each flag stone has rusted at the interface and leeched along the sporadic areas. Also the previous home owner did not protect the stone when trying to paint the rust on the railing, so there are local spots of black paint on the flagstone. Following stone has been weathered with a green mold like tone.

What is the best course of action in bringing this stone back to color and texture? Bleach, Acid, Vinegar, CLR, Homedepot brick cleaner, pressure washer? Thanks!