Pine
Is the least expensive material and is often used when painting your staircase.

Hemlock
Is basically pine without knots but also a little stronger, often used when varnishing or polishing to a lighter finish.

Mahogany (Sapele)
Mahogany (Sapele) is a very strong and durable Hardwood, often used when a darker finish is required.

Ash
Is also very strong and durable, often used when a lighter finish is required. It has a fairly similar grain to oak and often used as a cheaper substitute.

Oak
(American white oak) is many peoples favourite timber. Strong and durable and many peoples ideal timber.