When people picture a new floor, they think about colour, texture and plank width. Professional installers think about something else first: what is underneath. Subfloor preparation and the right underlayment determine whether a floor feels solid, sounds quiet, stays flat and lasts as long as it should. Many of the problems homeowners notice after an installation, such as clicking joints, soft spots, gaps or squeaks, trace back to what happened before the first plank went down.
What Is a Subfloor?
The subfloor is the structural surface your finished flooring sits on. In most Greater Victoria homes it is either plywood or OSB panels over floor joists, or a concrete slab in basements, garages converted to living space and many newer ground-level builds. Each type has its own preparation needs.
The Four Requirements: Clean, Dry, Flat and Sound
Clean
Debris, old adhesive, paint drips and dust can prevent floating floors from sitting flat and interfere with glue-down adhesives. The subfloor should be scraped and vacuumed thoroughly.
Dry
Excess moisture is one of the main causes of flooring failure. Wood subfloors and concrete slabs should be tested with appropriate moisture meters before installation, especially in older homes and basements. Victoria’s damp winters make this step particularly important. Moisture readings must fall within the flooring manufacturer’s limits.
Flat
Every flooring manufacturer specifies a flatness tolerance, typically measured over a set distance with a straightedge. Floating floors are especially sensitive. Dips cause planks to flex, which can stress the locking system and lead to clicking or separation. High spots create rocking points.
Structurally sound
Loose panels, squeaks and deflection should be fixed by screwing down the subfloor and, where needed, replacing damaged sections. A floor is only as solid as the structure under it.
Common Preparation Steps
- Removing old flooring and fasteners, staples or tack strips.
- Grinding high spots on concrete or sanding ridges on plywood.
- Patching low spots with cement-based patch compound.
- Self-levelling compound for larger uneven areas, poured to create a flat surface.
- Re-fastening plywood to eliminate squeaks.
- Undercutting door jambs so flooring slides neatly underneath.
What Does Underlayment Do?
Underlayment is the layer installed between the subfloor and the finished floor. Depending on the product, it can:
- Control moisture: a vapour barrier protects floors from moisture rising from concrete.
- Reduce sound: acoustic underlays reduce impact noise for rooms below, which is critical in condos.
- Add comfort: a cushioned layer makes floors feel softer and warmer.
- Smooth minor imperfections: though it never replaces proper levelling.
Choosing the Right Underlayment
For laminate
Laminate usually needs a foam or felt underlay, often with an integrated vapour barrier when installed over concrete. Some products come with attached pads. See our laminate flooring.
For vinyl plank
Many rigid core vinyl planks include an attached underlay. Adding a second, thick underlay can actually void some warranties and weaken the locking system, so always follow the manufacturer’s instructions. Browse our vinyl flooring.
For engineered hardwood
Floating engineered floors need an underlay suited to wood, often with a moisture barrier over concrete. Glue-down installations use adhesives that may include moisture protection. Nail-down installations over plywood typically use a building paper or underlay recommended by the manufacturer. Explore our engineered hardwood.
For carpet
Carpet pad affects comfort, durability and warranty coverage. A quality pad helps carpet wear more evenly and feel better underfoot.
Condos and Strata Rules
Many strata corporations in Victoria require hard flooring to meet specific sound-transmission ratings, often with an approved acoustic underlay. Check your bylaws and get written approval before you begin. We can help you choose a product and underlay combination that fits your building’s requirements.
Radiant Heating
If you have in-floor heating, both the flooring and underlay must be approved for use with radiant systems. Thick insulating underlays can reduce heating efficiency, so specialised products may be required.
Why Professional Preparation Pays Off
Preparation can feel like an invisible cost, but it protects the investment you can see. It helps prevent premature wear, keeps warranties valid and ensures the floor looks and sounds the way it should. Our installers assess every subfloor during the free in-home estimate, explain what preparation is needed and include it clearly in your quote.
Planning Your Project
Ready to start? Browse our flooring products, then request a quote or contact us. We serve Victoria, Saanich, Langford, Colwood, Esquimalt, Oak Bay, View Royal, Sidney, Sooke and beyond.
Signs Your Subfloor Needs Attention
If you are replacing an existing floor, the old one may give you clues about what lies beneath. Squeaks, bouncy areas, visible dips, cracked tiles, separating seams or musty smells can all point to subfloor problems. In older Victoria homes, settling, previous renovations and past water leaks are common. In newer homes, construction moisture and uneven concrete can occur. Identifying these issues before ordering material helps avoid surprises on installation day.
Frequently Asked Questions
Do I need underlayment for vinyl plank?
Many vinyl planks have an attached underlay. Only add an extra layer if the manufacturer allows it, and use a vapour barrier over concrete where required.
How flat does a subfloor need to be?
Each manufacturer sets a specific flatness tolerance. Your installer measures this with a straightedge and corrects any areas outside it.
Can I install new flooring over old flooring?
Sometimes, if the existing floor is flat, well bonded and approved by the manufacturer. Often, removal gives a better result.
Does subfloor prep affect my warranty?
Yes. Most warranties require that subfloor conditions meet the manufacturer’s specifications.