The bed does not have to be deep - heaths and heathers do not have deeply penetrating root systems. 8-9" should be sufficient, but you can do deeper if you like. I designed a large, 6' tall (at its tallest point) curved planter (an equivalent of a raised bed if you like) for a steeply sloped front yard with terrible drainage for a client that wanted a dedicated heather garden. 8 years later, all heathers doing fine.

I too grow heathers in terraced beds, because I garden on a steep slope. I dug down about a foot, but that was due to my having clay soil that I wanted to amend deeply. Pam's mention of 8-9" of amended soil (lean, porous) sounds about right; such raised (or terraced) beds will drain freely.

Rockspray's horticultural info is right on the money in my experience. Site them where sun can burn off morning moisture that settles onto them, especially if you're in a fog-prone area, but keep their soil moistÂthat plus sun and a light shearing in late winter.

Thanks I had seen heath and heathers in city owned ground
and called the head gardener, he admitted he'd had his workers remove the clay and put in rich well drained soil,before planting the heath and heather.
But I cant do that back breaking work. I over the years have collected rocks large ones! I will use them to make the raised bed perhaps line it and add well drained soil.
It is a present to my dtr.who lives with me she loves the
heather and heath. Thanks for the info I was worryed abt.
root depth. Marisa