Fill the reservoir on an airless spray system with acrylic masonry surface sealer. Instructions may vary between units, but, in general, open the door on the top of the reservoir drum and pour the sealer into the unit.
Connect the system to the nearest electrical outlet inside or outside of your home. If you are not able to plug the system directly into an outlet, use an extension cord that can handle the amperage for the spray system.
Begin spraying at the top edge of one side of the roof. Spray the acrylic sealer in a steady motion along the roof. Move the spray down so that it slightly overlaps the edge of the first sprayed area.
Continue down one side of the roof until you have sprayed all of the concrete tiles. Move to the other side of the roof, start at the top and apply the acrylic sealer in even rows.
Allow the sealer to dry for at least two hours. Touch the roof to see if the sealer still feels sticky. If the sealer is dry to the touch, apply a second coat of sealer using the airless spray system and the same method across the roof as used on the first coat.
Use a paintbrush to apply the acrylic sealer to odd-shaped roof areas, such as gables, and around fixtures, such as chimneys. Let the second coat dry for at least two hours before walking on the roof.