When I first had a Microsoft Windows personal computer I put it on a computer desk in the lounge and bought a typical office chair with five castors. Over the next few years wheeling that chair around the desk area with my weight on it seriously damaged the carpet in that location. So I had to find a way to prevent office-chair castors damaging carpets. See this discussion on the subject.
How The Damage Is Done
The damage is done when the weight on the castors pushes the carpet down into the underlay to form the shape of an inverted dome. These deformations permanently stretch the carpet in small areas and are made by all types of furniture with castors.
When the furniture is not moved about this deformation is often tolerated. Some people use castor cups to try and spread the load over a larger area to reduce the deformation.
When heavy furniture on castors is moved about, the carpet gets stretched by the rolling castor. Continual rolling in the same location stretches a large area of the carpet and pulls at the adhesive holding the upper layer to the backing until the two part company. The picture below shows a castor stretching an area of carpet due to the weight pressing down on it:
Different types of damage are done to different types of carpet. The damage is most noticeable on carpets which have a lightweight weave and pile and are then stuck to a fabric backing with something like a latex solution. The stretching caused by castor weight and movement breaks the upper part of the carpet away from the stronger backing. The carpet is then in two separated layers in the damaged area. The top layer with the pile is more easily stretched than the backing and becomes larger in area, where it is damaged. Wrinkles then form as the only way for this larger surface area to fit in the original area on the floor.
How I Prevented My Office-chair Castors Damaging Carpets
Because my computer desk was in the lounge (a room which must look presentable to visitors) and my chair caused damage to the lounge carpet I had to find a way to prevent the damage.
I had to be prepared to use whatever method would prevent future damage to any new carpet I might install. At the same time I needed that area to look as if it were carpeted like the rest of the room.
“Although my featured image looks like Christmas you will see, if you look carefully, my office chair standing on the mat. Unfortunately I never took specific photos of the mat as I wasn’t anticipating writing this article. This is the best I have.” — HC
I Made A Hardboard Backed Mat
I needed to protect the main carpet from any stretching by preventing the castors from coming directly in contact with it. That was resolved by putting a board over it that was about 1.2m square. I used hardboard approximately 3mm thick. Plywood may have also been suitable but would probably have been 6mm thick (too thick in my opinion).
The rigid hardboard worked to spread the weight of the castors over a much larger area of the carpet. This prevented them from sinking into it and stretching it. However having a sheet of hardboard spread over some of the lounge carpet doesn’t look very good. So I covered it with a mat made from an offcut of the same carpet.
I reasoned that because the mat would be laid directly on top of the hardboard, which doesn’t give under the weight of the castors pressing down like underlay does, it would stay flat and not get stretched. It might get a bit squashed but not stretched to the point where it would be seriously damaged. In the event my experience has proved this concept correct.
The Detail Of The Mat Construction
The diagram below shows my mat designed to prevent office-chair castors damaging carpets. It shows a section of the carpet cut away to reveal the hardboard underneath.
In my particular case I found I had two pieces of hardboard of a suitable size. So I taped them together on the smooth side with double sided carpet tape.
For my overlaying mat I used an offcut from the lounge carpet so that it wasn’t too noticeable. I had it bound around the edge at a local carpet shop. (Binding a mat stops it from fraying at the edge and often results in the mat having rounded corners.) I then stuck the mat to the smooth side of the hardboard with more strips of double sided carpet tape. I put tape all around the edge and added a couple of strips going from one edge to the other. The tape divided the hardboard into four equal parts. The edge of the hardboard was hidden by making the mat overhang it by 2 inches (50mm). To do this either the hardboard has to be cut about 2 inches (50mm) smaller than an existing mat or the mat made 2 inches (50mm) larger than existing hardboard.
The Mat Did Have A Problem
This mat lasted for several years. The only issue which became a problem was where the mat came into contact with the castors on the desk drawer units at either side of the sitting position.
The mat would move along the existing carpet towards the desk and to the right. I had to keep realigning it. Mats on top of carpets tend to do this according to the way forces on it are applied and according to the way the carpet pile wants to bend over with weight on it.
The mat’s overhang would curl up until the hardboard came into contact with the drawer unit’s castors. Over time the hardboard got chewed up at the edges by the drawer unit castors and would have required replacing. I didn’t have to replace it because I moved my computer desk to a spare bedroom where carpet protection was not required. So at that point I disposed of the mat.
How Well The Mat Protected The Carpet
When the desk and mat were removed from the lounge the chair had done no harm to the lounge carpet. The only permanent marks on the carpet were due to the weight of the desk drawer’s castors pressing into it. I hadn’t taken any action to prevent that. Looking back I could have made a much larger mat. It could have fitted under the desk and had the drawers resting on it too. They would probably have held the mat in position with their weight. By that design the hardboard would not have got chewed up. The downside would have been the need for more carpet since my existing offcut was not large enough.