If you can build a wood frame wall, you can divide one room into two with a partition wall, turn a carport into a garage by adding walls on the sides, or remodel a veranda into an extra room. You can frame an exterior wall on the ground and tilt it up into place. If the wall is an interior partition, you may prefer to build it already upright and in place, since there won't be room to move it easily.
Get planning permission from your local council for your project. Internal works need no planning permission. Plan for the wall to have a solid foundation. If it's a room divider, place it either across the floor joists or directly on top of a single floor joist. If it's an exterior wall, make sure the foundation extends below frost level so it won't heave in the winter.
Measure the length and height of the wall and calculate the materials. You'll need two pieces of two-by-four timber that are as long as the wall. One will be the top plate and the other will be the bottom plate. For an exterior wall, use treated lumber for the bottom plate. The rest of the timber will be for the vertical studs, which need to be approximately 7.5 (3 inches) shorter than the height of the finished wall to allow room for the top and bottom plates. To figure how many studs you'll need, divide the length of the wall measured in centimetres by 40 and add 1.
Draw a mark on the edges of both the top and bottom plates every 40 cm (16 inches). These marks show where the studs will go. If you want to frame a door or window in the wall, mark the inside edges where you want them to go.
Lay the bottom plate flat on the floor and nail it in place with 16-penny framing nails. If you want to build the wall on the ground and raise it later, simply lay the bottom plate on edge near where it will go.
Mark a line on the ceiling directly above each end of the bottom plate. You can use a plumb bob or hold one of the studs vertical according to a carpenter's level and mark its top. Nail the upper plate to the ceiling, aligned exactly above the bottom plate. If you're building the frame on the floor, lay the top plate in position the correct distance from the bottom plate.
Nail the studs between the top plate and bottom plate with 16-penny nails, using the marks spaced 40 cm (16 inches) apart as a guide. Center a stud on each mark, and add a final stud at the end of the wall, even if the spacing is less than 40 cm (16 inches). If you're building the frame on the ground, you can nail through the plates into the ends of the studs. If you're building the frame in a room, you'll need to drive the nails at an angle partway through the stud and into the top or bottom plate.
When you come to the area for a door or window, nail studs on either side, using the marks to align the edges of the studs rather than the centre so the full open space will be allowed. Measure the width of the door or window and cut one "two-by-four" that length for a door, or two for a window. Nail these crosspieces at the top of the door, or the top and bottom of the window, nailing through the vertical studs into the ends of the crosspiece. Cut additional studs just long enough to fit above the door frame, or above and below the window. Nail them in place, spacing one stud at least every 40 cm (16 inches).
If you've been framing the wall on the ground, lift it into place, check to see that it's vertical with a carpenter's level and nail it to the existing wall, floor or roof frame. The framed wall be ready now to cover with siding, wallboard, or however you want to finish it.
For extra strength in a load-bearing wall, use two upper plates nailed together.