How to Waterproof a Metal Shed Roof

Set the extension ladder to the lower side of the roof in a comfortable position so you can safely climb on to the roof on a dry and sunny day. The warmer the day, the better the caulk and paint will adhere and seal the roof. Use the broom and remove all debris from the surface such as limbs, leaves and any dirt. The roof should be clean before applying any sealant or silicone caulk.

Place the silicone caulk into the caulk gun and seal up any holes or open seams in the metal roofing. You may want to "dab" some silicone on the fasteners, nail or screw heads, to create an extra seal beneath the roofing paint. Allow the caulk to fully cure, approximately 24 hours, before applying the paint to the roof surface.

Open the canister of metal roof paint and thoroughly mix as per the manufacturer's instructions. The metal roof paint will contain particles held in suspension. These particles are what bind together with the metal surface to create a good seal for waterproofing.

Attach the paint roller to the extension handle and carry it along with the paint to the upper edge of the metal roof. You will want to begin painting the roof on the upper side of the incline and work downwards to the lower edge where the extension ladder is placed.

Apply the paint in thick even strokes, blending the paint together as you proceed across and down the slope of the roof. You will want to work with some diligence in speed as the paint will quickly dry against the metal surface on a warm sunny day.