United Kingdom 
My lawn is very wet for most of the year. I want to install a small patio, raised beds and cover quite a lot of the garden with stone chippings. My question is will I have a problem with algae on the stones if the water does not drain away sufficiently? I have looked into drainage solutions but have been told the mains drain is too high to create enough of an incline. I don't think a soak away would work as when I had a new fence put along the bottom of my garden the workman had to use a pump to keep the water out of the holes to allow the concrete to set.
4 Apr, 2018
Answers
Hi Kitty! Yes, pebbles and gravel do get algae. Is this a north facing site? A photo would be great, we would be able to see what your plans are in relation to what you have. :) But you wont solve this problem by covering it up.
4 Apr, 2018
I would retain part of it and have a bog garden - there are some very nice things that would grow there (sorry I know this isn't what you asked...)
5 Apr, 2018
Sounds like a plumbing issue. Look into getting the drain refitted. Algae on the stones? Structural damage to the house? Wood rot? Black mold? All are possibilities.
4 Apr, 2018