I had a carpet laid in my living room but the metal door strip has come loose so I tried to nail it back down but the nails are going in to some sort of old bitumen dpc so the nails won't hold. So what i was thinking of doing is to remove just enough bitumen and lay a sand and cement mix but as it's only be to a depth of 10-20mm would it be strong enough to drill so I can screw the carpet strip in place.