5.5mm plywood / plyboard SP101 (FG1) subfloor is the way to start a hard floor project

Assuming you have a wooden underfloor, then if you are fitting safety vinyl, marmoleum or LVT – and often wood, then a nice stable subfloor is the key to a professional finish. Where the amateur goes wrong is not enough preparation and an over-eagerness to get to the ‘fun# bit which is putting on the top floor. But unless you get the subfloor flat (we flatten floors in flooring, we don’t level them – that’s a builders job) you are always going to have a 2nd grade floor.

So, today we have been repairing and plyboarding a floor in Balham SW12 London for a client. Cutting the plyboard to shape, making it as tight as possible, securing it with coil nails and then next once it is all fitted we will prime it and the apply a self-levelling latex screed. This is allowed to dry – usually takes a few hours but often left overnight depending on weather conditions and internal temperature of the property, and then we return to give it a final sanding to leave a very smooth surface that is now ready for the top floor.

This is the best way. You can use a feather finish to just cover the cracks between the plyboards and this will save you some money on screed but latex screed gives the nicest finish and it flexes if there are micro-movements in the subfloor. The flooring grade plyboard is stiff and designed to minimize flexing and this stops the glue wearing out that attaches the top floor to the subfloor. Makes everything last a lot longer and prevents bubbling and the top floor coming away from the subfloor.

One final thing to note and something we always mention to clients is that if you have 2 different underfloors, so one made of concrete and one made of wood, you may see a wear layer appear over time as the wood will flex a little and micro stretch the top floor. There is nothing you can do about this save use one type of underfloor which is not always going to be practical and will often be very expensive.

Plywood floor