It works perfectly as a concrete expansion joint sealant.
Seal gap between concrete floor and wall.
However it s not that simple.
Remove the baseboard if present to expose the gap between the subfloor and the wall face.
After the walls have cured the basement floor is poured leaving a similar tiny gap known as the cove joint between the cured walls and newly poured floor.
Use a smooth even motion filling the crack flush with the surface beveling it if it s against the house.
Fill the crack with urethane caulk similar to what you would use for driveway caulk.
Snip the opening of the tube at a 30 degree angle making the opening the same size as your gap.
This will hopefully be the fix that keeps that wall of the sunroom nice and dry.
Slide the flat end of a pry bar between the baseboard and the wall.
Typically this will be cracks in your foundation.
The gap in question was previously filled with either fiberboard or concrete crack sealant but enough of it has deteriorated to conceivably allow moisture in.
In the short term a sealant applied along this gap between your basement floor and wall may prevent leakage.
However it will eventually fail in one of two ways.
Under ordinary circumstances this gap is too small to admit water.