Hi dotty:
My husband gets out there pretty soon and power washes. It seems to work really well. We use an environmentally friendly cleaner and all the patio, walkways, and slimy parts of the house even, look as good as new when he's finished. We actually even have algae (I think ) in our window frames. Our sport-court was really nasty and slimy last Spring & when he was done it looked brand new. The power washer was one of our first purchases after moving up here. We got it at Costco for a pretty reasonable price.

I think you can buy moss-out too as a spray or powder. If you don't want to purchase a power washer. We never tried that. I'm not sure how environment friendly that is. We just have been happy blasting it all off with the power washer.

We do have a pressure washer, but it is too light to get the really hard stuff off. When we rented a strong one, it blasted the gravel out of the exposed aggregate concrete. I can't win! You are likely lucky that your DH hasn't let it build up. I'm going to push for s mid-range washer. What is the name of the friendly cleaner that you use? Thanks for the reply.

I'd be interested to know what the Eco cleaner you use is also pacnwgadngirl. We have a PW but there are some areas that are more 'delicate' than others. Where it's washing (or the results thereof are washing) down into the garden, the standard bleach type things don't really work for me. Can you share with Dotty & I what you use?
Much appreciated.
Holly

Depending on how much mold you have, you should be able to pre-spray with a diluted bleach and water mix, let it work on the mold for say 15-30 minutes and then even a small pressure washer should work. By the time it's diluted in the mix along with the water from spraying, it's pretty harmless to plants.

Hi guys, I looked in the garage and shop but couldn't find it. I'm sure he got it at Home Depot. It was especially made for pressure washers and said on the package it was eco-friendly and safe for plants. I will find out the exact name for you. We are getting ready to take on this project again real soon and will be using it.

I'm sure boxofrox's suggestion is great too. A diluted bleach solution would work. I know, because the first time I ever used moss-out it bleached out all my clothes I was wearing, so bleach must be in it.

Thanks boxofrox. Yesterday, we had the bricklayer come back and look at the green wall -- it was just completed late last fall. He bought a product to spray on and it smelled like bleach but cost $10 a litre. He is going to seal those bricks again, obviously the seal didn't work the first time. I guess I'll go out and buy the biggest bottle of bleach I can today! I just hate the green and black mold that we get each spring.

Typically, even house painters will use this same diluted bleach solution to remove mold/moss prior to painting. It doesn't really have to be that strong and since it basically dries before you pressure wash, any runoff or spray will be pretty insignificant.

I think a good detergent and brush with sturdy bristles would do it good before painting. Some painters offer this kind of job prior to painting.

Here is a link that might be useful: newton painting