A basement scope that skips the slab is a guess.
Look for damp patches, efflorescence and evidence of past water entry, and confirm whether the chosen product calls for a moisture test.
Measure high and low points across the full slab rather than one room, and mark where grinding or self-levelling compound is needed.
Record crack width, any vertical offset and whether the two edges sit level, then decide whether the crack is stable enough to floor over.
Locate the floor drain, sump lid, cleanouts and any radon rough-in so they remain accessible once the floor is down.
Add membrane, panel, underlay and finish thickness together, then check the total against ceiling height, door swings and the bottom stair riser.
Shrink-swell clay is widespread under Calgary. Forensic engineering sources on expansive soils note that basement floor slabs are affected by clay movement to a much greater degree than footings, which is why heaved and cracked slabs are more common here than genuine foundation damage. That is the reason we survey the whole slab plane instead of assuming a basement is flat.
A dimpled subfloor membrane creates an air gap and a warmer walking surface, at the cost of height. Going direct to slab keeps the height but depends on a drier, flatter slab.
High spots are usually ground down and low areas filled with self-levelling compound. Which one dominates depends on where the slab has actually moved.
Every millimetre added underfoot shortens the bottom stair riser and changes thresholds at the mechanical room and the door to the garage.
Flooring Experts Calgary installs basement flooring in Calgary homes, and every scope starts with the condition of the slab underneath it.
Expansive clay sits under a great deal of Calgary, and it does not push evenly. Engineering sources on shrink-swell soils note that basement floor slabs move far more than footings do, which is why homeowners here find a heaved or cracked slab much more often than a damaged foundation. A basement can look perfectly ordinary and still be out of flat by a noticeable amount from one corner to the other.
That changes the order of the job. We survey the whole slab plane, not one room, and mark the highs and lows before anyone talks about colour. High points are usually ground back. Low areas are filled with self-levelling compound. A slab that has moved in the middle of a large open rec room often needs both, and the quantity of compound is a real cost line rather than a rounding error.
Crack assessment is separate from flatness. A tight, stable crack with both sides sitting level is a preparation item. A crack with a lip, where one side has lifted above the other, tells you something has moved and keeps the choice of finish narrower. Rigid plank tolerates a small amount of this. Tile is the least forgiving finish over a slab that is still working.
Basement floors are height projects as much as surface projects. A dimpled membrane, a plywood panel, an underlay and the finish itself stack up quickly, and that stack has consequences.
The bottom stair is the one people forget. Raising the basement floor shortens the bottom riser, and risers are supposed to stay consistent from top to bottom of a flight. We measure the existing riser height before choosing an assembly, and where the numbers do not work we say so early rather than at install.
Ceiling height matters in older stock. Calgary's 1960s to 1980s bungalow ring often has less headroom below than a newer suburban build, and adding forty millimetres underfoot is felt. Door swings, the mechanical room threshold and the entry from the garage all get checked in the same pass. So do the sump lid, floor drain and cleanouts, which have to stay reachable once the floor is finished.
Health Canada sets a radon action level of 200 Bq/m3. Where a home tests at or above that, mitigation normally means work at the slab: a penetration for sub-slab depressurization, plus sealing of cracks, the sump lid and other openings.
We do not test for radon and we do not install mitigation systems. That is separate work by a separate trade. What we do is sequence around it. If mitigation is planned or possible, the core drilling and sealing should happen before the finished floor is installed, not after. Cutting into a new floor to reach the slab is avoidable when the mitigation trade is booked ahead of the flooring date.
The same logic applies to any moisture work, drainage repair or framing that touches the slab. Get everything that penetrates the concrete finished first. Then the floor goes down once.
It is a judgement call, not a rule. A dimpled membrane or panel system adds an air gap, a warmer surface and some tolerance for minor slab dampness, but it raises the finished floor. Where ceiling height or the bottom riser is tight, that height has to be justified.
Often yes, provided the slab is clean, sound, dry enough for the product and within the flatness tolerance in the manufacturer instructions. Rigid-core planks bridge small surface texture. They do not correct a slab that has heaved or is still moving.
Many slab cracks are stable and can be prepared and floored over. What matters is width, vertical offset between the two sides and whether movement looks current. Where the two edges are no longer level, the crack is a levelling and product-selection problem, not just a cosmetic one.
No. Health Canada sets a radon action level of 200 Bq/m3, and testing and mitigation are separate work that we do not perform. It matters to flooring only because mitigation involves slab penetrations and sealing, so that work should be finished before the floor goes down.
That depends on the mechanical room, sump, floor drain and any framing still to come. We scope the floor around fixed equipment and access points so nothing that needs servicing ends up buried.
For early planning we use CAD ranges of $4 to $9 per square foot for vinyl and LVP and $2 to $6 per square foot for levelling. These are planning ranges for budgeting, not quotes.