Great question — answering as the UphillTech team:
As for the gaps between the bottom of the base board (skirting) and the floor ... that is normally covered over with a base shoe molding. Base shoe is a small dimension molding that can be pressed down to fit the variations in the floor surface. Base shoe molding is normally only skipped when carpeting is going to be installed on the floor. A nice trick regarding base shoe molding is to fully paint it (primer plus top coats) before it is installed. This way, after install, all that needs to be done is to fill the nail holes and do very small touch-up painting. It makes for a really clean look along the floor. If a pneumatic nailer is used to install the base show the nail hole size is...
Full answer by Michael Karas: https://diy.stackexchange.com/a/141224 (CC BY-SA 4.0).
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