Everything You Need To Know About Half Lap Joints
Half lap joints are a terrific skill for beginning woodworkers to master. Here's everything you need to get started.
For many woodworkers, the half lap joint is their introduction to basic wood joinery. While the history of the half lap joint dates to antiquity, they’re every bit as foundational and useful today as they were in the Roman empire.
What Is a Half Lap Joint?
A half lap joint involves joining two same-sized pieces of material by removing half the thickness of each piece where they connect. This creates a smooth, strong connection.
The name “half lap” derives from a “full lap” joint, which is simply laying one piece of wood over another and pinning them together with screws or nails. A full lap joint is so rarely used in woodworking that “lap joint” is more likely to mean a half lap.
Forming a half lap joint can be done with hand or power tools. Many woodworkers use a table saw or router to do most of the work, then clean up and shape the final lap with a chisel.
Types of Half Lap Joints
The most common half lap joint connects two similarly-sized pieces at a 90-degree angle, but there are a number of variations. Because there’s no central authority for woodworking, many of these joints go by different names.
Types of half lap joints include:
- Cross laps: Sometimes called a T-joint or T-lap, the overlap comes in the middle of one or both pieces to make a corner, rather than the ends.
- Mitered half laps: These have the clean appearance of a mitered end with the added strength of a half-lap.
- Dovetail cross laps: These create added strength and visual appeal. They’re a good choice for a visible lap joint, or to show off your precision woodworking skills.
- Scarf laps: The half lap pieces connect end-to-end, creating a linear extension instead of an angle. These can be used horizontally or vertically.
Half Lap Joint Common Uses
Half laps are strong enough to work in structural walls or frequently used household furniture. Here are some of the most common uses:
- Picture frames: Mitered half laps are particularly popular among frame makers because they provide secure fastening options while retaining the classic look of a mitered joint.
- Drawers and cabinets: Half laps aren’t as strong or attractive as dovetails. But they’re commonly used for drawers and cabinets, especially when the joinery is unlikely to be seen when in use.
- Structural framing: Many classic log cabin designs feature lap joints of one type or another. If you’ve seen Lincoln Log toys, you’ve seen lap joints in action.
Half Lap Joint Advantages and Disadvantages
Like most woodworking techniques, a half lap joint offers advantages and disadvantages. Most of its strengths and weaknesses are flip sides of the same coin, so be sure to consider your specific needs when deciding whether to use a half lap joint in your project.
- Simple to make: A half lap is easy to make and understand. Many beginners are more comfortable making something they can easily picture in their head.
- Easily reinforced: The broad flat surface of a half lap joint lends itself to securing with wood glue as well as physical fasteners.
- “Minimalist” appearance: Although some half lap joints use dovetails, miters or other details, the basic one is an unpretentious type of joinery. It’s a great choice for woodworkers who prefer a rustic or minimalist aesthetic.
- End grain reduced: A half lap joint reduces the amount of visible end grain, compared to a butt joint. While not eliminated, it greatly reduces the visibility of the end grain.
- Must be reinforced: Unlike mortise-and-tenon or dovetail joints with inherent design strength, a basic half lap joint must be reinforced with some kind of adhesive or fastener.
- End grain visible: While a half lap reduces end grain visibility, it isn’t eliminated. If it bothers you to see end grain, choose a different type of joinery.
- “Simple” appearance: Some people see streamlined simplicity, while others just see a simplistic design. Not everyone appreciates the looks of a half lap joint, and the simple aesthetic is not appropriate for every project.
Tips for Cutting Half Lap Joints
Creating half lap joints is a great skill for beginner woodworkers. Here are a few tips to get you started:
- The most popular way to cut lap joints is on a table saw with a dado blade insert. Use a miter gauge or sled to ensure safe, accurate cuts.
- If you don’t have a dado insert or your table saw doesn’t accept one, you can make a few passes over a single blade, creating cuts to depth. Then clear out the waste with a chisel.
- This same multi-cut method works with a circular saw, or even a miter saw with a depth gauge.
- If you’re using a hand saw, you can make multiple cuts as described above. Or make a single cut to depth, then use a clamp to hold the workpiece in place while you saw a vertical cut along the length of the lap.
- You may wonder if you can make that vertical cut on a table saw. This is only safe if you have a vertical cutting jig. If you don’t have a specialized jig to handle your material, stick to making multiple passes. It takes slightly longer, but is much safer, especially for beginners.
- No matter how you make your cuts, the clean-up is the secret of this joint. By making each connecting lap smooth and level, you’ll ensure a stronger, better-looking connection. You may find this fine-tuning frustrating at first. But the more you practice, the easier it will be.