Ask This Old House is back for a milestone 25th season! To kick things off, mason Mark McCullough travels to New Mexico to cross an item off his bucket list: working with adobe. Taught by a local expert, Mark learns how to make adobe bricks, a building technique used by cultures around the world for thousands of years, making it one of the oldest methods of construction still practiced today. Despite its ancient roots, Mark finds the process remarkably similar to making concrete. Afterwards, they patch a cracked earthen floor in an adobe house, creating a strong, seamless repair that blends right in with the rest of the floor.

Next, host Kevin O’Connor learns a new technique for creating perfect miters from general contractor Tom Silva. Tom demonstrates how to find the exact angle of an out-of-square corner using nothing but two boards of equal width and a pencil. Using that angle, he dials it into his miter saw, no time-consuming math required. The result? A perfect miter joint.

Finally, in celebration of Ask This Old House’s 25th anniversary, landscape contractor Jenn Nawada revisits a garden she helped revive more than 10 years ago. Back in season 15, Jenn used historic landscape plans the homeowner had to transform an overgrown yard into an idyllic space. In this episode, the homeowner shows Jenn how beautifully the garden has matured, along with some new additions to the backyard.

How to Build and Repair with Adobe

As a lover of all things masonry, mason Mark McCullough never passes up the opportunity to work with a new material. When he got the chance to work with adobe, a natural and traditional building material popular in the Southwest, alongside Paul Mallory, a local instructor from the nonprofit Adobe in Action, he jumped at the chance.

Where to find it?

Adobe in Action: Paul is a member of this New Mexico-based non-profit that educates people on how to design, build, and preserve adobe homes.

ADOBE INGREDIENTS:

• Sand: Quickrete medium sand or can be sourced locally from riverbeds.
• Straw: usually barely or wheat, locally sourced from farmers.
• Clay: sourced from Paul’s backyard. New Mexico has heavy clay soil.
• Water: from the hose.

ADOBE BRICK MAKING TOOLS:

• Adjustable window screen to sift clay.
• Wheelbarrow
• Mixing hoe: DeWalt 53 in. fiberglass handle mortar hoe to mix mud for bricks.
• Shovel

ADOBE FLOOR REPAIR TOOLS:

• Safety glasses
• Chisel: “Dasco Pro Cold Chisel Kit” to scrape away the existing damaged area.
• Hammer
• Flat chip brush
• Adobe mix = 4 parts sand, 3 parts sifted clay, water until mix is stiff
• Mixing tool: Paul used the discontinued “Marshalltown Adobe Spoon” to mix his dry adobe ingredients together.
• Mixing container
• Finishing trowel
• Smooth plastic sheet as burnishing tool: Paul used a thin, flat plastic cut from a yogurt lid or something similar.
• Linseed oil

How to Cut Perfect Miter Angles for Any Corner

No one likes a sloppy miter. Caulk may be able to hide the gap at the front or back of the joint, but it can’t replace good craftsmanship. With this trick from general contractor Tom Silva, you’ll be able to find the perfect saw angle for any miter—inside or outside corner—even if the corner itself isn’t perfectly square.

ASK 25 Revisit | Historic Landscape Design

At Ask This Old House, we relish the opportunity to breathe new life into historic homes and landscapes. Over 10 years ago, Jenn Nawada helped homeowner Alex revive an overgrown garden using plans developed by a protégé of landscape architect Frederick Law Olmsted. To celebrate Ask This Old House’s 25th anniversary, Jenn returned to see how that garden—and the rest of the yard—has evolved since.

Where to find it?

The original project episode was from Ask This Old House Season 15, Episode 18: Passage Set, Landscape.

Original Air Date: Oct 1, 2026, Season 25; Ep. 1 23:42

Products and services

Expert assistance: Adobe in Action

All products, tools, and materials can be found at Home Depot.