Hi, Firstly sorry if this is the wrong place to ask. Had a builder over who was removing old concrete steps to back door. We didn't want pave slabs done now and pretty sure talked about decking when he was here originally to let area dry out and we said it has to last at least a year. he quoted to replace the steps with timber after removing the original. After removing the concrete the floor is just pebbles like being on the beach. He's now put in a free standing timber frame that is covered in OSB boards which he sprayed with something. Apart from it obviously being wood I wouldn't have said it was timber or he should have said he was using OSB, feels misleading. As far as I was aware OSB shouldn't be used outside? Is this just going to fall apart and come off, I feel it's unsafe as it is ,as it's free standing on a couple of the removed paving slabs on the pebbles and about a foot+ from the door. So you have to stretch a bit. Mainly just trying to find out about OSB and if it will be ok and any other comments. I just don't want it needing to be done properly in 6 months again. Thanks!