Framing a structure
Get the base square and level, then everything above it is repetition. Errors at the plate multiply all the way to the roof.
Square at the base or nowhere
Everything in a framed structure references the plates at the bottom. If the base is out of square, every stud is out of plumb by the same amount, the sheathing will not lie, and the roof will not fit. Correcting it later means taking the frame apart.
So the base gets checked properly: diagonals measured and compared, not eyeballed. The 3-4-5 method sets a right angle with nothing but a tape, and comparing the two diagonals of a rectangle tells you whether it is square in one measurement each.
- Compare the diagonals
- Equal diagonals mean a square rectangle. One tape, two measurements, and it is conclusive.
- 3-4-5 for a right angle
- Any multiple works. 3 along, 4 across, 5 on the diagonal, and the corner is square.
- Check before nailing off
- A frame is adjustable until it is fixed and sheathed. After that it is not.
- Level matters as much
- An out of level plate puts every stud a different length, which is a day of correcting.
Mark the plates together
Stud positions are marked on both plates at once, laid side by side, so every stud lands in the same place top and bottom. Marking them separately guarantees a discrepancy, and a stud that is 5mm off at the top is a bow in the wall.
Centres are usually 400mm or 600mm to suit sheet materials, and the crucial detail is measuring to the centre of the stud but marking its edge, with a cross to show which side. That convention removes the commonest layout mistake, which is building half a stud width out.
- Both plates at once
- Laid together and marked through. Separately marked plates never quite agree.
- 400 or 600 centres
- So sheet edges land on studs. Getting this wrong wastes boards and adds noggins.
- Mark the edge, cross the side
- A line and an X. It removes the half a stud width error, which is the classic one.
- Mark openings first
- Doors and windows dictate stud positions around them, so set those out before the regular spacing.
Every stud has a crown
Timber is not straight. Sight along each stud and you will find a slight bow, and the convex side is the crown. Every stud in a wall goes in with its crown the same way, so the wall bows consistently and can be pulled straight by the sheathing.
Mixing the crowns is what produces a wall that is wavy rather than bowed, and a wavy wall cannot be corrected. It is the single easiest quality improvement in framing and it costs nothing but the habit of looking.
- Sight every stud
- Look along the edge. The bow is always there; the only question is which way it goes.
- Crowns the same way
- A consistent bow pulls straight under sheathing. Mixed crowns give a wave that does not.
- Discard the worst
- A stud with a serious bow or twist belongs as a noggin, not in the wall.
- Same rule for joists
- Crown up on a joist, so the load flattens it rather than deflecting it further.
Nailing patterns are structural
The number, size and position of nails in a framed connection is specified, not a matter of judgement, because those connections are what resist wind and racking. A stud is typically two nails through the plate at each end, and sheathing has a specified edge and field spacing.
Overdriving is the common error with a nail gun. A nail driven through the face of sheathing loses most of its holding power, and a whole wall overdriven is a whole wall of reduced capacity. Set the depth on a scrap and check it as the day warms up.
- Follow the specified pattern
- Count and spacing are structural. Extra nails do not compensate for wrong placement.
- Do not overdrive
- A nail head sunk through sheathing loses much of its hold. Set the depth and re-check it.
- Nail size matters
- Ring shank where specified. A smooth nail in the same hole is not the same connection.
- Keep clear of edges
- Too close and the timber splits, which is the same as no nail at all.
The two real hazards
Nail guns and circular saws, in that order. A nail gun in bump fire mode will drive a nail through a hand faster than you can react, and the injuries are disproportionately to the hand holding the work. Sequential mode is slower and it is what you use when accuracy matters or when you are tired.
A circular saw kicks back when the blade binds, which happens when the offcut pinches or the material is unsupported. Support both sides of the cut, let the blade reach speed before it touches the timber, and never reach across the cut line.
- Sequential over bump fire
- Bump fire is for volume nailing on a flat deck, not for holding a stud with your other hand.
- Hand well clear
- Nails deflect off knots and out of the side of timber. Assume the nail can come out anywhere.
- Support both sides
- A pinching offcut binds the blade and kicks the saw back at you. This is the classic saw injury.
- Disconnect before clearing a jam
- Air line off, magazine out. A jammed gun fires when it clears itself.
Frequently asked questions
- What tools do I need for framing?
- A framing hammer or nail gun, a circular saw, a speed square, a framing square, a tape measure, a chalk line, a 1200mm spirit level, a string line and a pry bar. Add a sliding bevel and a rafter square for roof work, and a cordless drill for fixings.
- What is a speed square used for in framing?
- Marking square and 45 degree cut lines fast, and guiding the saw along them. It also reads roof pitches and rafter angles from its scales, and its lipped edge hooks over the timber so it registers square without being held in position.
- What size framing hammer should I use?
- Around 20oz to 24oz with a straight claw. Heavier drives a nail in fewer blows and tires your arm faster, which over a day matters more than the blow count. A milled face grips a nail head and marks the timber, so it suits structural work rather than anything visible.
- What does crowning a stud mean?
- Sighting along a stud to find which way it bows, then fitting every stud in the wall with the bow the same way. A consistent bow pulls straight when the wall is sheathed, whereas mixed crowns give a wavy wall that cannot be corrected afterwards.
- How do I check a frame is square?
- Measure both diagonals of the rectangle and compare them. Equal diagonals mean it is square. To set a right angle from scratch, use 3-4-5: three units along one side, four along the other, and five across the diagonal gives an exact right angle.
- Should I use a nail gun or a hammer for framing?
- A nail gun for volume, because it is several times faster and it does not shift the timber with each blow. A hammer for anywhere access is tight, for adjusting, and for anything where you want to feel what the nail is doing. Most framers carry both.
- What spacing should studs be at?
- Usually 400mm or 600mm centres, chosen so that sheet material edges land on a stud. The spacing is set by the sheathing and plasterboard sizes rather than by the timber, and getting it wrong means cutting boards and adding extra noggins.
- Why is overdriving nails a problem?
- A nail driven so its head sinks through the face of sheathing loses most of its holding power, because the head is what transfers the load. A whole wall overdriven has significantly reduced racking resistance. Set the gun depth on a scrap and check it through the day.
