How can I build a concrete chimney cap?

A concrete chimney cap provides protection for your chimney, by channeling rainwater away from the chimney. Because it is wider than the actual chimney is, it acts like an umbrella for your chimney. Proper construction requires you to build a special wooden form that has about a 15-degree down angle and is about 3 inches wider than your chimney. Nail the form into place and trowel concrete into the form until it is filled on all 4 sides. As the concrete sets, insert steel reinforcement bars for added strength, and you are finished. When it is dry, take away the form and your new chimney protection is complete.