earthroof cheaper way without the mats

I wanted an earthroof but the drainage mats seems expensive and I dont have the roof strength. Is there a cheaper way to cover my roof. ?

The roof is currently covered with osb and is allmost flat. It is felted but has suffered water leeks. I was thinking of covering it with damproof but this would be exposed and may become cut. Is there something I could cover it up with that is cheap?

Ok what about covering it with bark and woodchippings, with a small layer of stones for drainage, anyone think this would work?

You might get some helpful replies if you give a little more info. What climate are you in (in particular, precipitation)? What is the slope of your existing roof? What is osb?

Here in the Himalayas we have flat earth roofs and no waterproof membrane or "drainage mat" (I'm not sure if you mean a waterproof membrane by that). But a flat earth made of round beams, willow sticks, and mud plaster is probably useless in most other climates.

Search for floor installers that have scrap tile floor under layment. And layer the scraps like shingles

i am in the uk, its pretty wet here at times.

the roof has a small slope alomst flat. OSb is like plywood 12mm sheets of timber.

i was thinking of putting a damproof course down and putting carpet ontop to protect it. This should work in theory but I wonder if any birds will peck at the carpet and pierce my damp proof course. I dont think the carpet would rot other than just soak up water.