Posted: 19/07/2013 at 08:07
I agreed with Verdun and Dovabove above. If you already have a membrane down adding more mulch is not going to help. Are the weeds growing through the membrane? If they are then you need to lift it, dig out what are probably perennial weeds and start again. If the membrane was out flown some time ago and/or is very cheap they do degrade and break apart.
if area roots are just in the mulch then they will be annuals and if you keep clearing them off they should reduce over time as any weed seeds in the mulch will be used up. you also need to think about where the weeds may be coming froHavel you lots of weeds in neighbours gardens? If so then you may to just accept that it will be an ongoing chore. It may be that the seeds were in the mulch, especially if its home composted?
another way of controlling weeds is to plant up the beds so there is not too much spare soil. Once the plants you want have spread and grown then there will be less space for weeds to grow and germinate. I know this also tait's time to achieve but at least you know the work will reduce over time.
If you want to mulch but can't afford the costs. The following can be used although I admit they aren't pretty to look at, they will gradually rot down cardboard, newspapers, harass cuttings. You could use the first two to add a barrier layer under your existing mulch.
Hope we have offered some help or glimmers of hope