Do I need a vapour barrier under LVP on a concrete slab in my Vancouver condo?

Yes — you should always install a vapour barrier under luxury vinyl plank (LVP) flooring on a concrete slab in a Vancouver condo, even though LVP itself is 100% waterproof. This is one of the most common points of confusion among homeowners, and the reasoning is straightforward once you understand what moisture can do beneath the floor.

While the vinyl planks themselves will not be damaged by moisture, water vapour migrating through a concrete slab can cause several problems. Trapped moisture between the concrete and the vinyl creates a warm, sealed environment where mould and mildew thrive — you will not see it, but you will eventually smell it. Moisture can also degrade adhesives if you are doing a glue-down installation, cause mineral deposits (efflorescence) on the concrete surface that push up against the planks, and in extreme cases create enough hydrostatic pressure to pop click-lock joints or cause planks to shift.

For floating click-lock LVP (the most common installation method in Vancouver condos), a 6-mil polyethylene vapour barrier is the minimum requirement over concrete. Many quality underlayments designed for vinyl plank come with an integrated vapour barrier — products like the thin foam or cork underlays rated for use under rigid-core SPC or WPC vinyl. If your LVP has an attached pad or underlayment on the back of each plank, you typically do not need a separate foam underlay, but you still need the poly vapour barrier beneath. Check your specific product's installation guide — some manufacturers explicitly require the 6-mil poly even with attached pads.

For glue-down LVP installation on concrete, a vapour barrier changes form. You cannot glue vinyl to polyethylene sheeting — the adhesive will not bond. Instead, a moisture-mitigating primer or epoxy applied directly to the concrete serves as both the moisture barrier and the adhesive prep. Products rated for concrete moisture mitigation cost $1.50 to $3.00 per square foot applied and are essential if your concrete tests above acceptable moisture levels.

Condo-Specific Considerations

Vancouver condo installations come with an additional critical requirement: acoustic underlayment to meet strata STC and IIC ratings. Most strata corporations in Metro Vancouver require a minimum of STC 55 and IIC 55 (many require 60 or higher) for any hard flooring installation. The underlayment you choose must serve double duty — vapour barrier protection AND acoustic performance. Products like cork underlayment with integrated vapour barrier or rubber acoustic mats achieve both functions. Budget $1 to $3 per square foot for strata-grade acoustic underlayment versus $0.25 to $0.50 for basic foam with poly.

Before purchasing any materials, check your strata bylaws and obtain written alteration approval. Many Vancouver stratas require you to submit the specific underlayment product with its tested STC/IIC ratings as part of the alteration agreement. Installing without approval — even with excellent underlayment — can result in forced removal at your expense if a neighbour complains. Strata application and inspection fees typically run $500 to $2,000 on top of your flooring costs.

The concrete slab in your condo may also need moisture testing before installation, particularly if it is a ground-level or below-grade unit. Upper-floor concrete slabs in newer buildings generally have lower moisture concerns, but ground-level parkade-top slabs and older buildings can have significant moisture transmission. A calcium chloride test or RH probe test costs relatively little compared to the cost of pulling up flooring to address mould six months later.

The total cost for a typical Vancouver condo LVP installation including vapour barrier, acoustic underlayment, and materials runs $7 to $14 per square foot installed, compared to $5 to $10 for a straightforward installation in a single-family home without strata requirements. The extra cost is unavoidable but well worth it for a trouble-free installation. Vancouver Floor Installers can connect you with contractors experienced in strata-compliant condo flooring installations across Metro Vancouver.

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