Exterior windowsills can help prevent window leaks. Homeowners can adhere wooden exterior sills to brick, stone, stucco and siding. The type of wood used -- either hardwood or softwood -- will have add an aesthetic appeal to windows and can prevent water damage. How the wood you choose is installed may also increase the life of the window trim.
Pine wood is a softwood type, which means it is more susceptible to water damage. However, soft wood is generally much less expensive than hardwoods, and is the more common wood-type used for interior and exterior construction.
Ash is a hardwood tree-type that can be used in exterior window sills. As a hardwood, with dense molecular struture, this wood type is more resistant to water damage and rotting. Ash works well in exterior window sills because of its durability. Ash is also an attractive wood, generally a light brown or greyish brown colour with a light grain.
Birch tree wood -- yellow, silver, river and paper -- is considered an "other soft hardwood," meaning the durability of the wood is between a soft and hardwood structure. It is a softer wood, but has higher density than, say, pine. The fine grain and almost white colouring makes an attractive exterior sill. Birch wood is a bit more expensive than other wood types.
Red or Silver Maple
Red or silver maple are both hardwood types. Because this wood type is more resistant to water damage, it makes a high-quality exterior window sill material. This type of wood has a high density and an attractive grain, with a swirling golden pattern.