Trim repairs: baserail replacement

Replacing the baserail on wooden stairs isn’t an everyday task, but it’s a recognised part of staircase renovation or repair projects. Homeowners take on this job to refresh the look of their staircase, improve safety, or fix damage. While not as common as replacing spindles or handrails, it plays a key role in more comprehensive staircase overhauls. In this case, I needed to replace the flooring, and the existing trim shape wasn’t ideal for attaching Scotia beading. I wanted a flat edge rather than a profiled one, and that edge had to extend all the way down to the concrete floor rather than floating above it. There were certainly other ways to get the job done, but I have a habit of choosing the complicated ones.

The demolition process required only three basic tools and involved splitting the existing baserail lengthwise to free the spindle bases. Once the spindles were gently pulled forward, they provided access to the infill. With the infill removed, I could reach the screws securing the baserail to the sill. The demolition part brought the most uncertainty to this project, luckily there was no damage to the existing woodwork and the rebuilding part of the project was carried over with calm (and taking more pictures).

Since the sill had pencil marks left by the previous crew and the varnish had discoloured the wood, determining the length of the new rail was straightforward. Measuring the existing rail wasn’t an option, as it hadn’t come off in one piece. I cut the new rail to length on my mitre saw and gave it a light sanding. Rather than trimming the spindles by a few millimetres, I opted to plane down the rail using my thickness planer. Removing material from either the spindles, the groove, or the back of the rail would have worked, but the last option seemed the easiest and quickest – so that was what I went with. I took a closer look at the wood grain direction and could tell that the base rail would only shrink in width, not in thickness. I was sure my alteration wouldn’t cause any wobbling in the future. Once it fit perfectly, I planed off the profiled edge at a right angle. Next, I attached the slat using glue and 18-gauge nails. The grain in the two glued pieces matched perfectly, making the new rail look like a single piece of wood. To clean up the glue squeeze-out, I used planer shavings, then planed the entire lip smooth.

After rounding over the top arris with a 6 mm router bit, and giving it a light sanding, my new baserail was ready for installation. I had to gradually slide it in from left to right rather than pushing it in, all at once, which would have put too much tension on the spindles. I slid the rail by hand, using a mallet to gently tap the spindles plumb. The process was relatively quick and required little force, just patience and light tapping – each spindle had to be tapped individually. The old rail had been removed differently, as its front lip had been cut away. Since the new rail had the lip intact, the installation process naturally had to be adjusted.

Once the rail was in place, I secured it to the supporting sill with 40 mm screws, making sure they were lightly countersunk so the infill would sit perfectly without any rocking. Cutting the infill to size was simply a matter of matching its length to the section below the handrail – copy and paste. Throughout the process, I occasionally used a spirit level to ensure the spindles were plumb.

Each piece of the infill had a slightly different length, and the outermost ones were completely different from the rest. One by one, I cut them to size and tapped them into place with a mallet. Overnight, the infill and the rail had been stored in different locations – the infill remained outside, while the rail started releasing moisture inside the house. As a result, the groove was quite tight for the infill – not too much, but it could be noticed. Once in place, I secured them with brad nails, filling the nail holes with wood filler and sanding them flat. Using small wire nails hammered in with a nail set might have produced smaller holes and a neater finish, but I opted for a power tool. I also considered glueing all the pieces together to prevent potential squeaking, but that could have made future disassembly impossible. Instead, I stuck to mechanical fasteners – unlike the previous carpenters, who had used both glue and nails, making their work more difficult to remove.

The other, shorter side of the rail had its lip fixed while in place. I glued in a small piece of timber, pressing it up against the rail with shims. The only thing left to do was to apply two fresh coats of varnish. I chose a solvent-based varnish to match the existing trim – despite the strong smell, it was the only way to ensure a consistent finish. From experience, I know the colour should blend in after about a year and a half. When I installed the new flooring, I had a chance to see if the new baserail worked with Scotia beading. Fortunately, its height was just right for the trim. I did wonder whether planing down the baserail was the best choice instead of deepening the groove, but it was certainly the quickest solution. I opted for the larger (21 mm) beading instead of the standard (16 mm). The two not only differ in size but also in shape, so I went with the more “luxurious” option. Thankfully, the beading and baserail worked well together. This project was full of uncertainty, requiring decisions at every step. Even now, I wonder if this was truly the best way to achieve a neat, professional finish. I may not have all the answers, but I’m glad the flooring is done – it works perfectly and looks great, not to mention it was completed almost entirely dust-free. As for the cost of materials, the entire job was surprisingly inexpensive. I won’t give exact numbers, but it cost no more than a six-pack of cheap beer.