Installing twin-slot shelving on a concrete wall
From A to Z and step by step, this post covers the entire process of installing a twin-slot shelving unit on a concrete wall. There are many ways to attach brackets to the boards, some easier than others, but the method shown below is my favourite. It’s neither too primitive nor too complicated. Everything can also be restored to its original condition – in other words, it doesn’t leave holes in the boards. Not to mention, there’s no need to visit the hardware store in search of pan head screws of very specific lengths. The whole process was divided into two parts: drilling into concrete and the woodworking stage. Having a proper SDS drill certainly made both parts enjoyable and predictable.
First, of course, I checked the wall with a detector to make sure the only hidden obstacle was the wire leading to the socket. As expected, it was running straight up, just as it should. Then I carefully marked all the drilling points, using a spirit level and tape measure to double-check that the lines were plumb and parallel. If they weren’t, I wouldn’t be able to swap individual shelves, as the distance between the brackets wouldn’t be identical. I made sure everything was accurate to within 1 mm. The uprights had four holes; I used only three of them, leaving the lower middle one without a screw.
Even though my SDS drill was equipped with a 2-in-1 chuck and could accept a 4 mm bit (not an SDS one), I used that bit with my 12-volt drill instead. That sped up the process. The 4 mm bit drilled all the pilot holes I needed, perfectly aligned and without slipping or wandering. I started slowly, focusing on accuracy at each drilling point. I ended up with six holes, 15 – 30 mm deep. The bit simply stopped at those depths since the 12-volt drill didn’t have a hammer function. Still, the holes were ideal for the next stage – proper drilling for the 8 × 40 mm plugs I planned to use. With all the pilot holes pre-drilled, I switched tools and finished the holes using an 8 mm SDS bit in my new hammer drill. All the preparation paid off: the results were 100% perfect. All six holes were beautifully aligned, at a 90º angle to the surface, and at the depth I needed – around 45 mm. I pushed in the plugs with my finger, setting them about 1 mm below the surface. For the screws, I first considered the shorter yellow ones but eventually opted for slightly longer silver ones. They provided better grip and looked neater with the white uprights.
I should mention that I’ve tried attaching the boards to the brackets with pan head screws in the past, but it’s not my favourite method, even though it’s quite simple. The only trick is to space the boards slightly away from the uprights – otherwise, they can’t tilt back and pop out. Another point worth mentioning is that I deliberately didn’t use my dust collector this time. I wanted to see the drilling point more clearly and get better results. The dust wasn’t a problem anyway – it simply fell straight down below the holes in an almost perfect line. My drill doesn’t have a cooling fan that blows dust all over the place – believe it or not, I used drills like that in the past!
I used a piece of scrap plywood for the bracket inserts – it had the perfect thickness for this project. The fit wasn’t too loose or too tight, just a perfect friction fit. Once I had the first insert traced, I set up my table saw and cut two larger pieces to length. The inserts had to be slightly smaller in both length and width so they could float inside the brackets. Friction alone held them in place. I’ve built many shelves this way, and there have never been any issues. The boards don’t move back, forth, or up – they stay exactly where they should.
I had to build a simple jig to safely cut the first pair of inserts. For that, I used double-sided tape to hold all the stop blocks firmly on a scrap piece of melamine. The second pair of inserts was cut using a different method, while for the third and final pair, I went back to the jig – this time slightly modified. All the stop blocks had to be removed and repositioned closer to the edge, as the workpiece got smaller with each cut. In the end, I had six inserts cut to size. I lightly sanded their edges just to remove any splinters.
The three boards were identical, just like the spacing between the uprights on the wall, which made the whole process much easier. I placed the first board on the brackets, perfectly centred, and marked the bracket positions from below. Without any measuring, I transferred those marks to the remaining boards and used my square to draw longer reference lines. The double-sided tape fit perfectly between the lines and held the inserts firmly in place. Unfortunately, the pencil lines couldn’t be erased, so they had to stay – but they were barely visible.
The assembly was a breeze, but it had to be done in a specific order – the same order would apply if the shelves are moved up or down in the future. I first placed the brackets into the uprights, then positioned the boards, pushing them back and down. The beauty of this method is that it allowed me to slide the boards all the way back. If I had used screws, I would have needed to leave a 10 mm gap from the uprights to allow for tilting. To reorganise the shelves later, I would simply reverse the process.
This method has both advantages and disadvantages. The good thing is that everything can be reorganised easily, and the boards have absolutely no holes. They’ll look like new forever and can even be reused in different projects. It also eliminates the need to hunt for screws of very specific lengths. In my case, the odd sizes were hard to find. I tried using what I had in stock, but the screws were either 5 mm too long or too short. Even if my approach doesn’t look easier at first, it is simpler for me. I think I got used to it from past projects, where shelf boards were super thin and didn’t allow screws from below. This method works every time – the screws don’t. Anyway, the shelves look great, and I also got a chance to test my new SDS drill and the pre-drilling technique. Everything turned out perfectly!
