A covered floor is an assumption
When the substrate is still covered, a tile proposal should state the assembly it assumes and should say that a different assembly, once uncovered, stops the work until the scope is rewritten. A figure written against a finished surface is an assumption about what is underneath. It is not a finding from an open floor.
Write the assumption as a sentence
Use a sentence a stranger could test after the first square of finish comes up. Examples that can be tested: a wood subfloor of a stated condition, concrete already flat enough to tile, or one layer of existing tile with a sound bond. "Standard conditions" cannot be tested. Pick the assumption the visible evidence supports, and leave the unknown as unknown.
Name the stop rule
The same page should say what ends the original scope. A second layer, rot, a cracked slab, or no backer where backer was assumed means the original sentences no longer describe the job. The next step is a revised scope before more work proceeds. Discovering the difference and continuing under the old sentences is how the document and the floor diverge.
A finished-surface photo has a limit
A photo of intact tile can show the room, the layout, and the fixtures. It cannot show bond, the number of layers, or whether the floor bounces. Use it as a picture of the finish. Do not treat it as evidence of the assembly under that finish. If the assembly matters to the scope, the proposal has to say it is still hidden.
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