How to Build Forms for Concrete Window Wells

Plan the size and shape of the form. Lay out a length of string or soft measuring tape to determine the total length that the plywood for both the inside and outside of the form must be. If the window well will not be curved, simply measure the length of each side.

Select the plywood that will be used for the forms. For curved forms, choose exterior plywood panels that have clear, knot-free and straight grain. Thinner plywood can achieve a smaller curve radius than thicker plywood. For example, while dry 1/4-inch plywood may be able to achieve a radius of 24 inches, dry 1/2-inch plywood can only reach a radius of 72 inches. Wet or steamed plywood can have a smaller radius.

Determine which way to orient the plywood if will be curved for the forms. If plywood is curved across the grain, it can achieve a smaller radius than if it is curved parallel to the grain.

Cut the plywood panels to size using a jigsaw.

Wet the plywood if it is deemed necessary to achieve a tight curve. Moistened plywood can be bent more easily.

Pound two-by-fours into the ground every several inches around the outside and inside of the planned window well form space. The plywood will be attached to these two-by-fours, so position them accordingly. Check to make sure that the tops of the boards are roughly level.

Attach the plywood to the two-by-four stakes. Bend the plywood gently to fit against the two-by-fours and use ample screws to secure the plywood to the forms.

Brace the forms using additional two-by-fours or similar boards. Angle the boards between the ground and the stakes so that the forms are well-supported and will not bend out or buckle when concrete is poured. Make sure that the forms are level and adjust the level of parts of the form by pounding stakes selectively.

Apply form lubricant, also known as form-release agent, or oil to the interior of the form before the concrete is poured.