I'm using 2 layers of 2mm thick wood floor underlay, the theory being that the first layer, which will be put down over all areas, will prevent any sound being transmitted to the plywood track bed even if some ballast escapes the track bed profile. The top layer, which will only be laid in the actual track areas, will help form the ballast shoulders and provide the primary sound insulation.

The following is a demonstration of the system using a short bridging section as a sample section. Please excuse the state of my 'workbench' but I can only do this sort of thing out on the balcony.

Tools used:- Scissors, Craft Knife, Felt-tipped pen, Glue Brush, Small Wooden Roller, Stain Brush.

Materials Used:- 2mm Closed Cell Foam Underlay, Masking Tape, PVA Glue, Water based Wood Stain.

Here's the plywood track bed with a couple of areas masked off where screws will fix it down to plywood risers. I don't want the foam to be glued down here until after the section is permanently fixed into position.

Here the foam has been roughly cut to shape, PVA glue brushed onto the plywood track bed and the masking tape removed to leave the 'non-stick' areas.

Here the foam has been applied to the plywood and the small wooden roller used to ensure overall contact. This was left to dry for 24 hours.

When dry a 50:50 diluted wash of wood stain was applied as I wasn't sure how strong the stain would turn out to be.

I had previously trialled various types of paint on the foam but found that, due to the smoothness of its surface, water based paint did not adhere well and solvent based paint had a tendency to melt the foam leaving a hard surface. Wood stain coloured the foam without affecting its properties and, once dry, did not come off.

After this had dried the full size track template was laid on top and the outline drawn with a felt tipped pen. The track template has been trimmed down so that there is a 5mm shoulder outside the sleepers.

The template was used again to mark and cut out the top layer of foam. This was then glued down to the first layer with PVA and rollered down. This was again left to dry for 24 hours.

Once everything was dry I then gave it an application of neat wood stain which, I think, now gives a good base colour to the track bed.

A check fit of the track template to make sure nothing had shrunk or moved and everything seems to be OK. The surface of the foam is still nice and supple so it's sound absorbing properties should still be intact. Track will be fixed down to the underlay using Copydex.

Finally here it is positioned back on the layout.

That's all for this installment but I have now established a methodology for laying the track underlay which will be applied to the whole layout.