How thick does your floor need to be? There are many factors that will determine how thick your floor needs to be. 1. The purpose of the floor. 2. The fitting technique. 3. Preservation Orders 4. The expected life of the building. 5. Board width and board length 6. Type of timber 1. The purpose of the floor. If you are using the floor for a domestic situation you are able to reduce the amount of timber being used and thus reduce the cost of the floor. On average a person will sand a floor once in a life time. If you use a good quality lacquer or if you follow the maintenance guidelines for your oiled floor you will be able to use a thinner top layer of engineered timber. I would suggest using a 3mm/4mm top layer of hard wood on a engineered birch/eucalyptus ply base. A good sander will take 1 mm of timber from the floor. On average a person will sand a floor once in a life time. This will allow you 3 to 4 sandings. 2. The fitting technique. If you are planning on nailing your floor to a ply base you will need to use a thicker timber 20mm or 21mm’s overall with a 4mm or 6mm top layer of hardwood. If you are going to glue the boards you are able to use a thinner timber. If you are going to float the floor on an underlay you can also choose thinner timber. 3. Preservation Orders If your building has a preservation order you may have to replace the existing floor with an exact match. Thus limiting your ability to use a thinner timber. 4. The expected life of the building. Modern buildings are designed to last somewhere in the region of 120 years and we aren’t going to live forever so using less material will allow you to save money. 5. Board width and board length The longer and the wider the board the thicker the plank of timber will need to be. A thinner plank will be more susceptible to movement. If you are looking for widths over 180mm I would suggest using a thicker timber. Either a 20mm/21mm board with a 6mm or a 4mm top layer of hard wood.