shiplap, inside corners

How to Install Shiplap Walls

Shiplap walls have gained in popularity in recent years, mostly due to their warm, “down home” appearance. This comes from the fact that many homes in the 1800s were built with shiplap walls. Originally developed for shipbuilding (hence the name), shiplap boards create a wall that is fairly waterproof when properly jointed and caulked, an important feature, when used for shipbuilding.

What makes it a shiplap is the way the boards are rabbeted to join together. The edges of the board are milled, forming a “step” or rabbet that fits together perfectly when the boards are mounted one beside the other. Sometimes, the top edges are bevel cut or beaded for decorative purposes.

You can either buy boards that are already shiplapped or you can make your own. Pretty much any boards can be turned into shiplap, simply by rabbeting in the step on a table saw or with a router. When using boards, ensure that they are not warped, twisted or curved, as that will prevent a tight joint.

Another option is to cut the shiplap boards from plywood, selecting a plywood which has a surface veneer that provides the look you are trying to achieve. Simply rip the sheet of plywood into 5-7/8” wide strips, being careful to maintain the plywood straight and flush with the fence, so that the pieces come out uniform and without wavy edges. The edges can then be rabbeted on the table saw or with a router, just as normal boards are. Cutting the plywood into 5-7/8” strips allows for 8 strips per sheet.

Materials Needed to Install Shiplap

You don’t need a lot of materials to install shiplap:

  • ⦁ Enough shiplap cut boards for the project
  • ⦁ Corner strips of the same sort of material (not shiplapped)
  • ⦁ Finish nails
  • ⦁ Wood putty
  • ⦁ Spacers 3/32” or 1/8” thick
  • Paint, stain or varnish to finish the wall

Quality shiplap boards are kerfed in two places on the back side. This is merely a couple of cuts, milled partially through the board (usually only about 1/3 the board’s thickness) and spaced evenly apart. The purpose of these is to account for expansion of the board, when it absorbs moisture. If the boards don’t have this, there is a change of the boards cupping when they expand and keeping that cup when they contract.

If your boards don’t come with these kerf cuts already in the backs of the boards, or you are making your own shiplap, you can easily cut them yourself on a table saw. Set the blade height to 1/3 the thickness of the board and the fence distance to 1/3 the width. Then run the board through the saw twice, flipping it around (but not flipping it over) so that you are making two cuts in the back side, splitting the back into three equal sections.

Tools Needed to Install Shiplap

Assuming that you are using precut shiplap boards, you will need:

  • ⦁ Tape measure
  • ⦁ Carpenter’s pencil
  • ⦁ Square
  • miter saw
  • ⦁ Table saw
  • ⦁ jigsaw (possibly)
  • ⦁ Pneumatic finish nailer & compressor
  • ⦁ Sandpaper (depending on your finish)
  • ⦁ Paintbrush & roller

Plan the Project First

Installing shiplap is simple enough, that many people just jump into the project, without thinking it through. That’s a great way to end up with a not so great job. While the actual installation of the shiplap is not difficult, what is difficult is making the job look perfect. Spacing is important to make your job turn out good, especially for the edges (ceiling, floor and corners) and around window and door openings.

You will need to decide if you are going to install your shiplap boards flush against each other or with a slight space between them. Adding the space accents the effect of the shiplap and allows you to nail the boards in the ensuing crack, making them all but invisible, even under close inspection. A 3/32” or 1/8” space is common in those cases where a space is desired.

Measure the exact height of your wall and calculate how many boards it will take to cover it. If you are adding a space between boards, don’t forget to figure this in. It is unlikely that your wall height will equal an exact number of boards. You are much more likely to end up with X number of boards, plus 4 inches. In that case, you are better off cutting 1” off of both the top and bottom boards, splitting that difference, than making one board that is considerably thinner than the rest.

Take into account how you are going to do your corners, as that affects the length of the boards. Corners should be installed first, allowing you to fit the shiplap to the corners.

It can be useful to mark where the studs are, in the wall, before beginning.

Taking the Floor into Account

Shiplap walls can be installed either with a baseboard or without. If you are not using a baseboard, then you will want to ensure that your bottom board sits flush on the floor. This can be a problem if the floor isn’t exactly level, as might be possible with a poured slab. In such a case, lay the bottom board on the floor and level it. Then scribe the floor’s profile on the board, by using a spacer and a pencil to follow the contours. The bottom edge of the board can then be cut with a jigsaw to sit flush with the floor.

Dealing with Corners

Typically, shiplap walls are only installed on one wall of a room, to provide an accent, although it is possible to install them on multiple walls or going around corners. If all you’re doing is a single wall, then the corners aren’t much of an issue. You can but the ends of the boards into the corner and it will look nice and neat.

Inside Corners

To ensure a neat inside corner, you can install a square strip of wood in the corner for the shiplap boards to butt into. This should be slightly thicker than the thickness of your boards, rather than the same height. If you try to make it the same thickness, then any differences in the boards or any movement in them due to absorbing moisture, will be extremely obvious. But if you use a thicker piece, those irregularities won’t be so noticeable.

The other thing you will need to do with these corner pieces is to relieve the back side of them. If you put a carpenter’s square in most inside corners of a house, you’ll see that they really aren’t 90 degrees. This isn’t an error on the part of the contractor, but rather that the process of finishing the drywall creates a buildup of drywall mud in the corner, altering the angle.

To overcome this, cut a chamfer on the back corner of the corner piece, as shown in the diagram below. Then the piece should sit neatly into the corner, allowing you to nail it in place.

shiplap, inside corners
Shiplap inside corners

Notice the relief cut on the end of the shiplap board, where it butts up to the corner piece. This is somewhat exaggerated to make it visible. But if you cut the ends of your shiplap boards with a two to three degree bevel, it will help ensure that your shiplap boards but up well against the corners. Otherwise, there is a possibility that a high point or the cut not being quite square could cause there to be a gap in the visible face, while the back edge is snug up against the corner.

Outside Corners

Outside corners are slightly more complicated for shiplap walls, than inside corners. You really don’t want to try to miter your corners, for two reasons. First of all, just like the inside corner, the outside isn’t exactly 90 degrees, for the same reason. Secondly, any contraction or shifting of the material, would cause there to be a gap right in the middle of your nicely mitered corner.

For these reasons, shiplap is almost always installed with a corner piece on outside corners. As with the inside corner, you want this to be slightly thicker than the shiplap board, so that it hides any irregularities in the thickness of the pieces. There are a few different ways that you can install these corners.

shiplap, two-piece, outside corners
Two-piece
shiplap, single-piece, overlapping, outside, corners
Single-piece overlapping
shiplap, single-piece, rabbeted, outside, corners
Single-piece rabbeted

The left corner is made by nailing two pieces of lumber in place. However, this can leave a gap in the seam between the two pieces, either due to the corner not being exactly at 90 degrees or due to shrinkage. This potential problem can eliminated by using a single piece, as in either of the other two diagrams.

To make the corner in the right diagram, a square cross-section piece of lumber has a rabbet cut out of the inside corner, either by ripping it on a table saw or using a router. Either way, it turns the piece of trim into a cap, which can then be attached to the corner.
In all cases, you will end up with a better fit if you relief cut the ends of the shiplap boards, so that the outer surface mates up with the corner and not the inner side.

Installing the Shiplap

With the corner pieces in place, installing the shiplap is easy. Work from the bottom up, starting by ensuring that the bottom piece is level. You can either press the pieces tight up against each other or allow a slight gap in the overlap. If you are going to leave an overlap, be sure to have some sort of shims that you can use as spacers. Regularly check that the pieces are level and that they are not gradually tilting to one side.

Leaving the gap between the boards allows you to nail the shiplap boards to the wall, hiding the nails in the gap. Be sure to only nail where the studs are, so that the nails will have something to anchor into. If you are not using a gap, you will need to fill the nail holes, so that they are not obvious when the wall is finished.
Any windows should be framed around, like corners, allowing you to butt the ends of the shiplap boards into the trim. Alternately, you could install the shiplap boards right up to the edge of the window frame opening and then cap the ends of the boards with some sort of decorative architectural molding.

The top piece is the last and needs to be cut carefully to ensure that it meets the ceiling evenly, all the way across. Any gap between this board and the ceiling will tend to make the whole wall look crooked.

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