We often get asked, ‘how do I prepare my subfloor’ and it is a very important question. If your subfloor has not been properly prepared and checked then it may cause damage to your wooden floor in the future. You should always prepare your subfloor before installing any wooden flooring, it should actually be seen as part of the installation process.
What are the main different types of subfloor?
First of all, the subfloor is the existing floor in your property underneath any carpet, vinyl or wood. These are the main types of subfloor that you may come across:
• Wooden floorboards
• Chipboard
• Plywood
• Concrete or screed
• Joists
• Asphalt
• Bitumen
How do I properly prepare my subfloor?
Check whether the subfloor is flat
Firstly, you must check that our subfloor is flat. If you have an uneven subfloor, your wooden flooring will not sit on top correctly. You will need to check that the entire subfloor is flat. Do this by using a straight edge or spirit level. Any unevenness of more than 3mm needs to be addressed. On a concrete subfloor, ridges and dips can be smoothed out using a self-levelling compound. On a wooden subfloor, you can line the surface with plywood boards.
Check whether the subfloor is dry
Most importantly, you need to check that the subfloor is fully dry. If there is any moisture, it can transfer through to your wooden floor and cause damage. The correct moisture meter should be used, depending on whether you have a concrete or wooden subfloor.
• Use a 2-pronged moisture meter for a wooden subfloor. The reading needs to be 16% MC (Moisture Content) or below.
• Use a Digital Hygrometer for a concrete subfloor, which needs to be left in place for at least 24 hours. The reading should be no more than 65% RH (Relative Humidity).
Do not install your wooden flooring if the subfloor is not fully dry. You will need to allow sufficient time for the subfloor to dry natural before re-testing the moisture content. 
Check whether the subfloor is clean
Finally, check whether the subfloor is clean. You will need to remove any existing wax, oil, adhesive or paint from your subfloor before laying your wooden floor. Then make sure your subfloor is fully clean to ensure there is no dirt or dust on the surface. When your subfloor is flat, level, dry and clean, you can start to install your hardwood flooring. Please, always read the installation instructions before fitting your wooden floor.
