How to Change & Build a Stone Fireplace

Cover the original fireplace design using a plywood frame. Take accurate measurements of your existing fireplace and create a frame that sits flush with the stone construction.

Build a frame to support your new stone construction. When building this frame, it's important to keep in mind the width of the stones you're using (flagstones don't require as wide a frame as cultured stones). Use a staple gun to cover the frame with a water-resistant barrier such as waterproof paper.

Install a metal diamond mesh lath to act as a base for your mortar application. Affix it over the entire surface of your frame using galvanized nails.

Create a template by laying stones out in their intended pattern in front of the fireplace. Building a template allows you to make sure that the stones vary in color, size and shape throughout the fireplace. To get all of the stones to fit, you may need to cut or chip some of them using a circular table saw or hammer.

Mix the mortar until it has the consistency of cake batter. Add water slowly until you're able to get the right consistency and then use that same formula for every batch of mortar you make.

Apply ½-inch of mortar to the lath in small workable sections (enough to apply two or three stones) using a trowel. Start at the top of the fireplace in order to avoid mortar dripping onto already applied stones. The first stones should be applied in a corner, moving outward.

Scrape a thin layer of mortar onto the back of the stone you're applying and press it into the mortared lath. Apply enough pressure so that some of the mortar squeezes around the edge of the stone. Hold it in place for a few seconds to ensure a strong bond before adding another stone. Work in sections and spread the task out over several days if necessary.

Prepare the grout the same way as the mortar. It'll need to be mixed a bit thinner so that it doesn't clog the grout bag. Fill the grout bag and then begin inserting the grout into the spaces between the stones.

Clean up the fireplace using a whisk broom to remove any excess grout or debris once everything is dry.