The 28 day rule and why it is real
Fresh concrete contains a large amount of mix water that has to leave before a coating can go over it. Twenty-eight days is the industry convention for a slab to reach a workable moisture state, and it is a minimum rather than a guarantee: a slab poured in November in an unheated garage may take considerably longer. We test rather than count days, but we will not even quote a coating on concrete under four weeks old.
An empty room is a cheaper room
On an occupied garage, somebody has to move everything out, store it for two days and move it back, and either that is your weekend or it is on the quote. On a new build there is nothing to move. The crew also gets clean access to every wall and corner, which is where hand edging happens and where time gets spent, so the labour on an empty floor is genuinely lower for the same square footage.
The first winter matters more than any other
Raw concrete takes up road salt and water immediately, and the damage from the first few winters is not visible until it starts spalling years later. Sealing the slab before it ever sees a salted vehicle means the concrete never absorbs any of it. If a new garage is going to be coated eventually, doing it first is both cheaper and materially better for the slab than doing it in five years.
Sequencing with other trades
Floor coating wants to be near the end: after drywall, after painting, after anything that produces dust or drops material, and before cabinets, shelving, racking or equipment. Where cabinets are going in, coating first and installing over the cured floor is the better order, because it leaves a continuous floor with no unfinished strips and lets the cabinets be moved later without exposing bare concrete.
Want this answered for your slab?
Free site visit with a moisture reading, then a written fixed price. Across the BC Interior.