Building Raised beds ontop of weed matting?

[Madame Mucksprout]

We want to make raised beds, laying them ontop of windy concrete pathways and compacted clay soil covered in 40 years of brambles, nettles and bindweed.
Options include clearing the whole site and laying weed-matting down with filled frames ontop. So we wont be able to dig below the weed-matting. Does that sound viable? Can you foresee any problems?

[veggiechicken]

Depends on what depth of soil you can provide in the raised beds. If you want to grow root veg, they'll need to be quite high.

[burnie]

I've done something similar, however a couple of things, weed matting will not stop more tenacious roots from coming through and your soil depth limits what you can grow, my Parsnips are often "L" shaped where they hit the membrane and then carry on growing, not a problem except for digging them up. I grow shorter carrots too.

[Mark_Riga]

If there are lots of nettles etc, I personally wouldn't cover with membrane and then put compost on top as it must be quite fertile to feed the weeds. I had nettles, willow herb thistles and docks but not bindweed in a very stony area. I cleared all the top growth one winter, about 2 year ago and put some wooden raised beds on top. Then filled it with compost from a loose heap I had, about 4 to 6 inch depth. Some thistles come through still and willow herb did for a year or so but the main problem I had was annuals from the compost heap.
Any perenials that did come through, I took out at least 4 inches of root each time I pulled them.

[SarrissUK]

I agree with Mark - I wouldn't bother with the weed membrane, and focus on getting decent depth in the raised beds instead