Thanks for your comments. Thanks DA for your thoughts on the matter. I will contact the gardener and see if they will be willing to come out to remove the soil and plants and to replant them. At the time of planting I had noticed tape coming away on one of the planters but he reassured me and said taping it down is not required as the weight of the soil will seal it. Hopefully he will remember saying that and do it at no charge otherwise it will be a very expensive mistake. I am going to look into how much it will cost to make the custom DPM, hopefully they are not too expensive. As for the carpenter, I will have to pay him to come out and remove the caps and put them back once the DPM is fixed. Thank you all!
The DPM just needs to cover the inside like a bin liner, it doesn't need making, cutting, sealing or anything fancy. Lay the DPM over the planter, make some drainage holes where the bottom will be, fill it with soil, trim the excess, job done.
Ah, I see. I thought the DPM came as a sheets on a roll which is why the carpenter cut it up and duck taped it.