we once had a job in tooting bec mental hospital in the late 70s, it was a hospital ward we were sanding, and the main contractor wanted all the gaps filled in , we sanded the floor off to a fine finish so the job would normally be complete and ready for sealing,so to deal with the gaps we mixed up decorating size and the dust from the sanded floor in a bucket to a thick creamy mix , then we spread the whole area with a screeding trowel, so the whole area was covered, once this was dry we sanded the whole area off with fine sandpaper ,which takes it off very easily , the floor was then swept off and three coats of ronseal hardglaze was applied, all sealed in ,perfect.these were just normal gaps which otherwise would have been normal to have sealed over ,bigger gaps were always filled with a putty and paint colouring mix to blend in with the colour of the wood. this contractor was over fussy , so we done it this way successfully.
