"effi" wrote in message
...
in building up a raised (10" or so) garden area on the front of a slab on
grade house,

is a gravel base for drainage wise or is regular soil fine?

maybe a combination?


Kinda hard to answer, a lot of variables.

1: how would excess water run, away from- or towards the structure(house).
Best to check that, water seeks it's own level and a soil mass (garden area)
would retain/hold/expel moisture.
2: type of soil. Clay will hold moisture but once saturated, becomes unable
to sponge it up. Sand or sandy loam will drain quickly.
3: type of plants. Some will soak up all the moisture they can get hold of,
shallow rooted plants such as rhodo's, ornamental cedars etc.
4: climate where you live incl. rainfall averages.

Look, just my opinion but.... I for one have never ever ever seen a
perfectly level slab. Soil shifts, concrete changes with time, etc. Drainage
is essential to growing plants, so drainage is worth planning for. Simplest
way: dig a subsoil trench all around the garden bed, 4 inches wide, 4 inches
deep, i.e.shovel size, including around the part that abutts the house. Try
to dig a continuous trench. Fill with gravel, then put soil over that. Any
sudden water excess will at least partially find that gravel trench and be
directed away from the house. Unless of course that part leans towards the
house.

Use as much biomass, compost as you can, acts as a sponge.

--
John H. Immink

www.renaissancegardens.com/