Cold Frame Construction Guide

Prepare your lid by cleaning the glass and frame with mild soap. If using a salvaged window, remove old hinges and repaint the frame with exterior paint, resealing any gaps with silicone sealant.

Measure and cut the lumber to match the dimensions of your lid. For an angled design, cut the back boards longer than the front boards (e.g., four boards high at the back and three at the front) to create a slope toward the midday sun.

Create the angled side pieces by drawing a diagonal line from the top rear corner to the lower front corner of a board and cutting along that line with a circular saw.

Assemble the box frame. Drill pilot holes first to prevent splitting, then screw the side boards, front boards, and back boards into corner battens using deck screws.

Install interior braces using scrap wood in the corners to secure the frame. Sand down any rough or uneven edges on the exterior of the box.

Position the lid onto the frame so it is flush at the back. Secure the rear of the lid to the frame using outdoor-grade hinges and mounting screws.

Install support battens (two short and two long) to allow the lid to be propped open for venting on sunny days. Optional handles can be screwed into the front of the lid.

Place the completed cold frame in a level, south-facing location directly onto the soil, concrete, or slabs to maximize light exposure.