Replacing a floor furnace grate requires removing the old grate, measuring the width and length of the floor opening, selecting the replacement grate and installing the new grate. It is best to measure the floor opening twice to avoid purchasing the wrong size grate.
Floor furnace grates, sometimes referred to as grilles or registers, are typically made of wood or metal. The heavier models stay in place on their own and are usually removed when pulled forward and then out of the opening. Some models are held together by screws that would need to be removed.
Manufacturers list the air duct measurements on their packaging, so the actual hole needs to be measured. The floor hole measurements should match the measurements of the lip on the inside of the grate, not the outer edge. Grates come with different size borders that help to cover up any gaps or uneven edges.
Selecting a replacement grate is usually easier at retail outlets such as the Home Depot and Lowe's because they have such a wide assortment. Some are specifically made for floors and are heavy-gauge steel or cast iron. Decorative models sometimes have a nickel or bronze finish with a decorative design.