"Tunnel construction" 






  Early in the planning stage it was decided that the Barna Railway would require two small tunnels. We had decided that the large conifer in the flower bed should not be moved as there was just enough room to allow a single track to go around the back of it. However I needed to build a tunnel to protect the trains from damage as they passed behind it. The second tunnel would be built at the corner of the shed to conceal the entrance to the storage sidings which are located inside.

Both of these tunnels were built before any track was laid to prevent the track from being accidentally damaged by falling rocks. But a short section of track was always on hand to test the clearances to ensure that the trains would fit through.

These two images show the locations for the two tunnels, they were both built using the same construction method. The following explains how the conifer tunnel was built back in November 2006.   

With the track bed fixed into position behind the conifer, the first job was to trim away the leaves from the back and side, this gave enough clearance for the framework to be installed.


 As you can see from this image there was just enough room to get the track bed around the back of it.

The framework was constructed using 12mm marine plywood, it is glued using a good quality waterproof wood glue and then screwed together.

Inside the tunnel are blocks of timber helping to support the roof. The tunnel roof will have a lot of weight placed on it so it must be well supported.

With the tunnel frame completed it was time to cover the plywood with some mineral felt, which was left over from the track bed. I first painted the plywood with a felt adhesive, which is a messy job (just look at the wall) and then stuck the mineral felt to it.

This should give good protection from the rain and prevent rotting.

Now it was time to start placing the rocks around the tunnel frame, this was a tricky job to do.

 I had plenty of rocks to choose from so it took a while to see which rocks fitted together the best.


The sides of the tunnel mouth were cut with an angle grinder to get the right shape. The rock over the tunnel mouth is held in position with stainless steel banding which was screwed into the back of rock and to the top of the framework.


I left spaces between the rocks which I filled with compost and planted some small conifers and rockery plants.


Here is the finished tunnel it only took half a day to complete but it adds a nice feature to the railway, and keeps the trains away from danger.

The finished tunnel

"Click on the image to enlarge"


With the heavy building work completed it was now time to get some track laid, click the track laying link at the bottom of this page to continue.

Click on the contact me link if you have any questions or comments.

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