Framing Layout and Lumber

Good framing starts before the first nail. You have to know what the lumber really measures, which way it bends, and where each piece goes. A framer who lays out correctly makes the sheathing, drywall, cabinets and trim fit. A framer who is off by 1/2 inch at the start makes every trade behind them cut and shim.

This guide covers wood framing for houses and light commercial work. Dimensions and spacing here are common practice under the International Residential Code (IRC). Your plans, your local code and your engineer come first.

What You Will Be Able to Do

• Convert nominal lumber sizes to actual sizes and read a grade stamp.
• Sight a board for crown and set it the right way.
• Lay out a plate at 16 inches on center so the sheets land on framing.
• Prove a corner is square with the 3-4-5 method and with diagonals.
• Pick the right nails and store lumber safely.

Nominal and Actual Sizes

A 2x4 is not 2 inches by 4 inches. That name is the nominal size, from before the board was dried and planed. The actual size is smaller. Learn this table, because every cut and every stack-up depends on it.

Notice that from 2x8 up, you lose 3/4 inch of width instead of 1/2 inch. That matters when you figure out header heights or the depth of a floor.

Reading the Lumber

The Grade Stamp

Each piece of framing lumber carries a stamp. It tells you the grading agency, the mill, the species, the grade and the moisture level.

Grade and species both change how far a joist or rafter can span, so you cannot swap them to save money. If a span table on the plan assumes No. 2 Douglas fir, that is what goes in.

Pressure-Treated Lumber

Pressure-treated (PT) lumber resists rot and insects. It is required where wood sits on concrete or masonry at a foundation, and in other locations the code names. Three things to know:

• Modern treatments contain copper, which corrodes plain steel. Use hot-dip galvanized or stainless fasteners and connectors rated for treated wood.
• Treated wood is often wet and shrinks as it dries.
• Wear a dust mask and gloves when you cut it, and wash before eating. Never burn scraps.

Engineered Lumber

Some members are made in a factory. LVL (laminated veneer lumber) is used for beams and headers. I-joists have a thin web between two flanges. Never notch a flange, and only cut holes where the manufacturer's chart allows. Follow their guide and do not treat them like solid lumber.

Crown and Defects

Almost every board bends a little. Sight down the narrow edge from one end, with the board at eye level. A high side that looks like a gentle hill is the crown. Mark it with an arrow.

• Joists and rafters go crown up. Weight on the floor or roof then pushes the bow down toward level. A joist installed crown down sags more every year.
• Studs go crown the same way along a wall so the wall stays flatter. Set the worst ones aside for blocking, or use them for short cuts.

Other defects to catch before you nail:

Storing and Moving Lumber

Lumber arrives banded in lifts. Stack it flat and off the ground on blocks spaced close enough that it does not sag. Cover it loosely so air can move.

Warning: A strapped bundle is under tension. Before you cut the bands, set extra blocking so the stack cannot flip or slide when the strap lets go. Stand to the side, away from the strap's path, and keep others clear.

Keep material near where you will use it, but do not overload a deck. Spread loads over supports, and do not stack bundles on a floor that has not been fully nailed down.

On-Center Layout

On center (OC) means the distance from the center of one framing member to the center of the next. Common spacings:

A tape measure is marked for this. Most tapes highlight every 16 inches, often in red, and show small diamonds every 19.2 inches.

The goal is for a 48-inch-wide sheet to end in the middle of a stud or joist. That way, the sheet has something to nail to and the next sheet shares that same stud.

Laying Out a Plate

Here is how to lay out a wall plate at 16 inches OC. Your stud is 1-1/2 inches thick, so its edge is 3/4 inch before its center.

1. Tack the plates together. Lay the top and bottom plates side by side, flush at the ends. You will mark both at once so they match.
2. Hook your tape at the starting end of the wall.
3. Mark 15-1/4 inches for the first stud edge. That is 16 inches minus 3/4 inch.
4. Continue at 31-1/4, 47-1/4, 63-1/4 inches and so on. The tape's 16-inch marks make this easy, because every mark is just 3/4 inch behind a highlighted number.
5. Square a line across both plates at each mark with a speed square.
6. Place an X on the side of the line where the stud goes. Crews usually put the X just past the line, away from the start.

The edge of the first sheet now lands at 48 inches, on the center of the third stud.

Use letters for other parts. Many crews mark K for king stud, J or T for jack or trimmer, C for cripple, and H for header. Mark openings first, then let the regular layout run straight through them. Keep the on-center marks going across a door or window, so the cripples above and below land on layout.

Use the same starting end for floors, walls and roof where you can. When studs, joists and rafters stack up in line, loads go straight down and ducts and pipes have clear paths.

Snapping Lines

Chalk lines show where the walls go on the deck. Measure both ends of the line from a known edge, hook the string, and snap. For a long run, have a helper hold the center down and snap each half. Use blue chalk for lines you may need to change or that will be seen later. Red is hard to remove, so use it only where a line must last.

Checking for Square

Square means a true 90-degree corner. If a floor or wall is out of square, everything built on it inherits the error.

The 3-4-5 Method

A triangle with sides of 3, 4 and 5 has a perfect right angle. This comes from the Pythagorean theorem: 3 squared + 4 squared = 5 squared.

1. From the corner, measure 3 feet along one line and mark it.
2. Measure 4 feet along the other line and mark it.
3. Measure between the two marks. If it reads exactly 5 feet, the corner is square.

Larger multiples are more accurate. Use 6-8-10 for a room, or 12-16-20 for a deck or foundation.

Diagonals

For any rectangle, the two diagonals must be equal. Measure corner to corner both ways. If they differ, the frame is out of square. Move it until they match.

Worked example. A floor is 24 feet by 36 feet. The diagonal should be the square root of (24 x 24 + 36 x 36).

• 576 + 1,296 = 1,872
• Square root = 43.27 feet, or about 43 feet 3-1/4 inches

Measure both diagonals. If one is 43 feet 2 inches and the other 43 feet 4-1/2 inches, shift the frame until they are equal.

Choosing Nails

Nails are sized by penny, written with a "d". Bigger numbers mean longer nails.

Guns use a variety of nail diameters, so follow the code and engineered schedules exactly. A shorter or thinner gun nail is not always a substitute. Common nailing patterns from the IRC include two 16d nails through a plate into a stud end, and face nails at 16 inches on center through a double top plate.

Common Mistakes

Check Your Understanding

1. You need to stack two 2x10s on a wall. How tall is the stack?

Each is 9-1/4 inches wide, so 18-1/2 inches.

2. You sight down a joist and see a gentle hill on one edge. Which way does it go?

Crown up. The floor load will flatten it.

3. What is the mark for the fourth stud on a 16-inch layout, if the first edge mark is 15-1/4 inches?

15-1/4 + 16 + 16 + 16 = 63-1/4 inches.

4. You measure 8 feet and 6 feet from a corner, and the diagonal is 10 feet 1 inch. Is it square?

No. A 6-8-10 triangle should read exactly 10 feet. Adjust until it does.

5. You need to build a deck ledger with treated lumber. Can you use regular bright nails?

No. Copper in the treatment corrodes them. Use hot-dip galvanized or stainless fasteners.

Key Takeaways

• A 2x4 is 1-1/2 by 3-1/2 inches. Know your actual sizes.
• Joists and rafters go crown up.
• Pull layout from one point. Do not measure piece to piece.
• 16 inches on center is the standard for studs and joists, and sheets land on it.
• Prove square with 3-4-5 multiples and equal diagonals.
• Block a bundle before you cut the bands.