The best product to fill the gaps between your floorboards and skirting boards is our clear sealant Selleys 655FC Fast Cure Adhesive Clear Sealant.
Selleys 655FC Fast Cure Adhesive will not shrink, it is flexible and can be painted with water-based paints only, if needed once it has cured.
An alternative solution is Selleys Roof & Gutter Silicone Sealant, however the silicone can not be painted in this product.