How do I handle an uneven basement floor when installing flooring in Calgary?

Most Calgary basement floors have some degree of unevenness, and addressing it properly before installing finished flooring is critical to a lasting result. Concrete slabs settle, crack, and shift over time — especially in Calgary where bentonite clay soils expand and contract with moisture changes, and chinook-driven freeze-thaw cycles create subtle but significant ground movement beneath foundations.

Start by assessing the severity of the problem. Place a long straightedge or level across the floor in multiple directions and measure the gaps. Minor unevenness (less than 3/16 inch over 10 feet) is normal and most floating floors like LVP can accommodate it without issue, provided you use a quality underlayment that compensates for small irregularities. Moderate unevenness (3/16 to 1/2 inch over 10 feet) requires a self-levelling compound, which is a cement-based product that you pour over the slab and it flows to create a flat surface. Self-levelling compound in Calgary runs about $2.00–$4.00 per square foot for materials and $3.00–$6.00 per square foot professionally applied, depending on the depth needed and the size of the area.

For severely uneven floors (more than 1/2 inch variation), you may need to grind down high spots first using a concrete grinder, then apply self-levelling compound to the low areas. In extreme cases — particularly in older inner-city homes in Inglewood, Bridgeland, or Kensington where original slabs from the 1940s–1960s may have significant heaving — you might need a full slab overlay, which adds $5.00–$10.00 per square foot to the project. Before investing in levelling, investigate why the floor is uneven. Active heaving or settling suggests a drainage or soil issue that needs to be addressed first, not covered up with levelling compound.

Before pouring self-levelling compound, the slab must be clean, free of paint or sealers, and primed with a bonding agent. Any cracks wider than 1/4 inch should be filled with a flexible crack filler first, and active moisture issues must be resolved — self-levelling compound will not adhere properly to a wet slab. If you're dealing with both moisture and unevenness, a raised subfloor system like DRIcore at $3.00–$5.00 per square foot can bridge minor unevenness while also providing a moisture barrier and thermal break, potentially eliminating the need for levelling compound altogether.

While a handy homeowner can tackle small areas of self-levelling compound, larger pours require experience because the product sets quickly and mistakes are difficult to fix. Get matched with a basement flooring professional through Calgary Basement Remodeling for a proper assessment of your slab condition and the most cost-effective levelling approach for your specific situation.