Thanks for all the responses!

The area we are working on already has some plants and fixtures in it. The more we thought about it, the more reasons we came up with for not using weedmat. It seems it might work well for a new garden with gravel 'mulch', but the long term for an organically mulched area is that it will either be high maintenance or just not work as it should because there will be nutrients above the weedmat to foster weed growth.

So, we've ditched the idea of weedmat, and sent the landscaper off to look for better mulch.

woodbe.