Subfloor preparation

A flat, dry and structural subfloor is essential for a quality finished floor. Issues in the subfloor will immediately or eventually cause a problem with the rest of the floor system. Subfloor work is far easier to complete in the correct order before the floor is installed, trying to fix after the fact is often impossible. Unfortunately, since the subfloor is out of sight, mistakes or neglect are too often hidden underneath. “Building a strong foundation” is a cliché metaphor for a good reason.

We believe in ingrained quality. This means having the ability and resolve to get every stage of a build to the highest standard. Subfloors do not need to be pretty, it is often messy work, but it is essential that it is functional, strong, flat and dry. The National construction code (NCC), industry standards and manufacturers all require minimum standards and tolerances to be met. Our capable estimators and installers are committed to meeting and/or exceeding these requirements in every job with any subfloor type (Concrete slab, bearers & joist, particleboard, plywood, battens, existing timber floors etc.).

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It is not uncommon for a subfloor to need some work and it is usually pretty straight forward. When the work is more involved it may take more time and resources but it is almost always possible to fix.

Sections of the floor are either raised or lowered to achieve a flat and level surface. For concrete this might involve pouring self-levelling compound or grinding back high points. Joists and battens can be packed up or planned down. Existing timber, particleboard and plywood would usually already be on a flat and level substrate but these too can be packed up by additional sheeting or sanded flat.

Moisture is probably the most common cause of damage to floorboards. It is essential that the subfloor is dry when the floor is installed but it is also essential to safeguard against future subfloor moisture. Concrete slabs on a ground floor or new slabs will need a moisture vapour barrier. This is usually achieved by either painting a barrier onto the slab or using a plastic sheet. A timber framed construction should have good subfloor ventilation, water should not be allowed to pool or flow under the house and minimum height clearances should be met. Suspended floors (upper levels) are usually safer from rising moisture but in certain circumstances, care should still be taken.

Structural integrity
Thankfully, most subfloors will be pretty strong to start with. This consideration is more commonly a factor for older constructions that have deteriorated. In timber framed construction, twisted, rotten or insect damaged bearers and joist can be replaced, if fixings have come loose, new fixings can be added. Concrete is more difficult to repair.

Please keep in mind that it is not always possible to predict all subfloor work. Sometimes, you won’t find out precisely how uneven a subfloor is until work has commenced, or it might only be revealed that there is structural damage that needs repairing after the existing layers have been removed. At SE Timber, we understand that unexpected costs and delays can be highly stressful. We try to present you with a rough 'worst case scenario' so you can better prepare for additional subfloor prep (hopefully it wont be necessary). We won’t start additional works until you have understood the situation and given us consent to continue.