In homes built before the 1980s, assume old flooring and mastic may contain asbestos until it has been tested.
Roy was built out mainly between the 1960s and the mid-1980s, and a great many of those houses have had a bathroom added downstairs at some point since. That is the distinctive tile job here, and it comes with a complication the upstairs bathrooms do not have: the floor is a concrete slab in contact with the ground, and moisture moves through concrete. A tile floor laid over a slab without accounting for that behaves differently from the same tile laid upstairs, and the failures look different too.
Concrete in contact with soil carries moisture, and a basement slab from this era may have been poured without a vapor barrier beneath it. Tile itself does not mind, but what goes under and around it can: certain adhesives fail in constant damp, and a moisture-sensitive floor covering installed over a wet slab will fail regardless of workmanship.
The practical signs are worth knowing. Efflorescence — a white powdery deposit — on the slab, a dark damp patch that never fully dries, a musty smell in the room, or previous flooring that lifted or discolored from beneath. Any of those is a reason to test before choosing materials rather than after.
Where moisture is present, the options are real rather than cosmetic: a moisture-mitigation coating on the slab, choosing an assembly that tolerates damp, and dealing with the source where it is identifiable — grading and downspouts outside being the usual and cheapest place to start. A tile floor is a reasonable choice over a damp slab precisely because it tolerates conditions that other coverings do not, but the installation has to be specified for it.
Concrete cracks. Most slab cracks are shrinkage from curing and are stable, and tile can go over them with the right treatment. Some are moving — because of settlement, because of a slab on expansive soil, or because the two sides are at different levels — and a tile floor bonded directly across a moving crack will crack in the same line, usually within the first year.
Telling them apart is the installer’s job and it is a legitimate part of the preparation. The usual answer for a stable crack is an uncoupling or crack-isolation membrane, which lets the slab move slightly without carrying that movement into the tile. For a crack with vertical displacement, or one that has clearly moved recently, the right answer is to find out why before tiling over it.
Movement joints are the related point. A tile floor needs joints at the perimeter and across large areas, and in a basement that butts up against foundation walls, leaving those out is a common shortcut that shows up later as tile tenting or cracking along a wall.
A bathroom added to a basement has plumbing that was retrofitted, and retrofit plumbing in a slab varies enormously in quality. Before tile goes down it is worth knowing whether the drain falls correctly, whether a shower drain is where it needs to be for the layout you want, and whether there is an ejector pump involved — because moving a drain in a slab means cutting concrete, and that decision belongs at the start of a project rather than the middle.
Ventilation matters more in a basement bathroom than upstairs. Without a properly ducted fan taking moisture outside, a basement shower raises the humidity of a space that already has limited air movement, and the result shows up as mold on cool surfaces rather than as a tile failure. A fan venting into a joist bay or an attic is not a solution.
So the order of work is: confirm the drains and the venting, do any concrete cutting, build the wet-area assembly with proper waterproofing, then tile. Tile is the last ten percent of a basement bathroom and the first thing anyone asks about.
Usually yes — tile tolerates damp better than most coverings — but it needs specifying for the conditions rather than assuming. That deposit is efflorescence and it means moisture is moving through the slab, which can cause certain adhesives to fail. Test the slab before choosing materials, consider a moisture-mitigation coating, and check the cheap external causes first: grading and downspouts next to that wall.
Not by itself. Most slab cracks are shrinkage from curing and are stable, and an uncoupling or crack-isolation membrane lets the slab move slightly without carrying it into the tile. A crack with vertical displacement between the two sides, or one that has clearly moved recently, is different — find out why before tiling over it. Perimeter movement joints matter too; leaving them out is a common shortcut.
Ventilation and the drain. A basement shower adds humidity to a space with little air movement, and a fan that vents into a joist bay or an attic rather than outside leads to mold on cool surfaces. On the drain: if a shower drain needs to move for the layout you want, that means cutting concrete, and that decision belongs at the start of the project rather than halfway through.
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