Adding an interior wall

The addition of an interior non-load bearing wall is a fairly simple, affordable and short project that allows for the creation or division of rooms anywhere in the home.

Procedures vary depending on whether the home is under construction or already built. In the case of new constructions, walls are built on the ground before being erected into place (this is possible because the ceiling has yet to be installed), whereas in the case of a renovation project, it is recommended that new walls be built in their final upright position, which will be the topic of this guide.
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Choice of Materials
Should the Floor Covering be Removed?
1. Mark Wall Location
2. Installing the Plates
3. Installing the Studs
4. Installing the Cross-Studs
5. Finishing the Wall

Choice of Materials

There are two options: wood or metal framing. Walls constructed with wood are usually built using studs measuring 38 mm × 89 mm × 244 cm (2 in. × 4 in. × 8 ft) or 39 mm × 76.2 mm × 244 cm (2 in. × 3 in. × 8 ft). In general, 39 mm × 76.2 mm (2 in. × 3 in.) framing studs are recommended for these types of renovation projects. If you are extending an existing wall, measure the width of the original wall to ensure that the materials you purchase have the measurements required to match the width of the new wall to that of the old one.

If you choose to use metal plates and studs, this type of construction does not require cross studs and allows you to use shorter screws than if you were to use wood studs: 25 mm (1 in.) to fasten the plates to the ground and 6 mm (¼ in.) to fasten the studs to the plates.

Should the Floor Covering be Removed?

Walls may be built directly on top of wood floors as well as parquet and linoleum flooring. This allows the floor to remain intact should you decide to remove the wall. However, if the floor is covered in carpeting or ceramic tiles, it is recommended that these types of coverings be removed in the area where the wall is to be erected in order to facilitate installation.

1. Mark Wall Location

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The location of the new wall depends in part on the alignment of the ceiling joists. If the joists are perpendicular to the line of the new wall, you can install it almost anywhere, preferably against a stud in the existing wall (the wall into which the new wall will be anchored). However, if the ceiling joists are parallel to the line of the new wall, it will be fastened to a single joist only. In this case, the location of the new wall will be determined by the joist nearest to the intended location. As most floors are typically solid enough to serve as anchors, the floor joists are not as important, but if you are able to fasten the wall into the floor joists using screws or nails, it would be even better.

1.1 

Using an electronic stud finder, determine the alignment of the ceiling joists along the intended line of the new wall. If the joists run parallel to the new wall, go to step 1.2. If the joists are perpendicular, determine the location of the stud in the existing wall upon which the new wall will be anchored, and mark the location of the centre line along its entire length. This mark will serve to identify the starting point of the new wall line.

Note: You can try to find studs in your wall by tapping your fist lightly on the wall and listening for changes in resonance but this method is far from accurate.

1.2 

Place a framing square flat on the ceiling with one of its edges touching the existing wall so that the right-angle of the square is lined up with the centre line of the stud previously marked (or in-line with the centre line of the ceiling joist if the new wall is being fastened to a single joist). Trace a line on the ceiling along the edge of the square, of at least 45 cm (18 in.) in length, on a right-angle with the existing wall.

1.3 

Using a small nail, fasten the end of the chalk line to the middle of the line you just finished tracing. Place the chalk line over the existing line and mark the rest of the wall line. If the new wall is to be anchored to a single ceiling joist (parallel), fasten a second small nail to the joist where the new wall will end (fasten it to the centre of the joist) and wrap the chalk line around the nail before marking the line. In this way, the line will span the length of the joist along its centre and along the entire length of the new wall.

1.4 

Trace another line along the floor surface directly underneath the wall line on the ceiling. To do this, fasten a small nail at either end of the ceiling line and hang a plumbing bob from each of the nails, one after the other. The plumbing bob pointer will indicate the exact location of both extremities of the previously traced ceiling line on the floor below. Mark these two points on the floor and generate a line between them using the chalk line.

1.5 

Using the stud finder, find the exact location of each of the ceiling joists (if they are perpendicular) as well as the floor joists (optional) along the lines you just made. Using your carpenter’s pencil, mark both sides of each of the joists with 15 cm (6 in.) lines: it is important that you be able to locate these marks once the plate is in place because you will nail or screw between these marks (into the joists).

1.6 

If the ceiling joists are perpendicular to the new wall, proceed to the next step. If the joists are parallel, you must find and mark the location of the cross-stud or the single stud in the existing wall along the lines of the new wall in order to identify the areas where screws or nails may be inserted. Mark the edges of the cross-stud using the same technique as for the joists (6 in. lines).

2. Installing the Plates

2.1 

After cutting your plate to the required length, align its centre along the trace line on the floor and fasten it with screws according to the marks traced in step 1.5. Repeat the same process for the top plate. Some assistance may be required to complete this step.

On a concrete floor, use a construction adhesive to glue the sole plate to the floor before nailing it in place with a concrete nailer. Another popular method is to pre-drill the concrete (prior to applying the adhesive) to a depth of 25 mm (1 in.) before fastening the sole plate in place using masonry screws. The masonry drill bit is usually included in the packaging for the masonry screws.
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