Here’s my guide to making tunnels for your railway, the trauma free way.
Building tunnels on model railways is a lot easier than for engineers at Network Rail. They have to blast, drill and cut through tons of rock.
Thankfully, for us it’s just a matter of some messy work with cardboard, polystyrene and even the odd Pringles tube.
How To Make Straight Tunnels
For straight tunnels, I find it easiest to create the fabric of the tunnel and then fashion the hill around it. This is typically done using a preformed tube of some variety. I’ve previously used plastic plumbing pipe but any stiff cardboard tube will work, even Pringles tubes have been used – hat tip to Andy Carter for the idea!
Find a tube that’s double the vertical clearance for your trains. Whatever tube you use, cut horizontally — along the tube — just past half way around on both sides and place it over the track. Once positioned, the sides and top are built up with plaster or papier-mâché to create the surrounding hills or maybe just blocked off if you’re creating a town scene tunnel.
I prefer this approach as it’s clean and safe for your layout, with the track protected by the tube while you work on the surrounds. It’s also easy to apply tunnel wall decoration as you can just flip over the tube, work on the insides of it and then position it.
But making tunnels with tubes has one big drawback.
They are only usable for straight sections of track. If your tunnel is curved, following a bend in the track, another approach is needed.
Which takes me neatly to the second technique.
For curved tunnels I construct the broad shape of the hills/mountains either side of the track and once I’ve built up sufficient hight the roof section is added.
On my N scale layout, I build up the sides with polystyrene foam sheets. These are cut and positioned to get the general shape required and once I’m happy they are glued in place with a liberal coating of glue (see the best glue for Polystyrene foam)
For bigger scales, larger hills and mountains polystyrene foam sheets can still be used but it may be quicker and cheaper to use bulkier materials. Insulating foam works well for OO and HO scale. For really big builds, a wooden frame is built with a cardboard mesh bridging between the woodwork. I covered this previously in how to build beautiful hills on a budget.
Whether you use polystyrene, insulting foam or wood, the tunnel is shaped to match the curvature of the track — remembering to leave enough clearance on the inside for the trains.
With the tunnel and hill side in place, I then add tunnel wall effects. Lately I’ve been using photographs of actual tunnel walls (off the Internet) and scaled down in a photo editing application as covered here. In the past I’ve also used pre-printed wall card — such as the Noch Basalt or Sandstone paper card — which is easier but less rewarding.
The tunnel is then covered over using the same material as the surrounding hills to create the roof and the surface texture of the hillsides and vegetation added using scatter materials and static grass. This is no different to any other grass and tree work so shouldn’t present a challenge.
Extra: Tunnelling Tips
Don’t Forget The Walls: The inner walls of the tunnel will be visible from the entrances so don’t leave them blank. See here for a quick how-to-guide on this.
Tunnel Track Work: Like tunnels walls, the track will be visible for someway into the tunnel so make sure you continue any track ballasting and weathering well into the tunnel.
Test The Track: Once the tunnel is sealed it’ll be difficult to fix track problems so test, check and retest your trains run smoothly on the track before starting on the tunnels. Trust me, it’s more than a little annoying to build a tunnel on a station approach only to find your passenger coaches can’t get through!
Hidden Handy Holes: There will be times when trains get stuck in the tunnel so give yourself a means to recover or push trains from within the tunnel.
A long pole that can follow the curve of the tunnel is one option, for bigger tunnels an access hole is useful. This can either be through the baseboard underneath or perhaps hidden below a carefully placed building on the hill side so as not to spoil the look.
Making tunnel portals
With the hills and tunnel shaft made all that remains are the tunnel portals.
You can make these from cardboard and then glue photographs of the stone and brick work onto it to give surprisingly lifelike finish. It’s the same technique as for the inner tunnel walls above and is covered in how to create outstandingly realistic model railway scenery.
Alternatively, and arguably easier, are the pre made tunnel entrances and supporting walls from Hornby, Busch, Noch, GuageMaster, Peco and Metcalfe. A wide range of styles and brick/stone effects are available via these manufacturers in both N, OO and HO scales from model shops and online at eBay.
I’ve used the Peco and Busch portals on several of my layouts and have been pleased with the end result, they add greatly to the interest and mystery of trains disappearing into tunnels.
To finish, watch this video of how the tunnel that covers many of the concepts.
Did you know, you can get all my latest tips, reviews and guides direct to your inbox? It's completely free. Just subscribe to my newsletter and I'll do the rest. Click here to start. Thanks Andy, creator and founder of MRE.
Affiliate notice: Some links on this page will take you to carefully selected businesses, including B&Q, Rapid Online, Amazon, eBay and Scale Model Scenery, through which you can buy products mentioned. These links are made under their affiliate schemes which means that although the price to you doesn't change I get a small commission on the orders you place. Please see the disclaimer for more details.