Try the SX Rainproof Exterior Caulk from Siroflex which is rain resistant immediately after application and once fully cured can be over painted with water based and synthetic paints, the company says. The product can be used for sealing and filling gaps and cracks where movement can occur such as perimeter sealing between wooden and metal window and door frames and connection joints between concrete, brickwork, windowsills, stairs, ceilings, walls, metal sheets, thresholds, panels, aerated concrete, plasterboard and lime-stone. This one component, high quality acrylic sealant can be used for interior applications as well as exterior; it has good adhesion without a primer on painted wood, anodised aluminium and PVCu. After application the product forms a soft flexible rubber seal which has high elongation at break and high movement accommodation.