Saturday, July 28, 2018

How I constructed a boiler house for the sawmill using foamboard

After completing the sawmill for Peckforton Station (see How I constructed the sawmill), I realised I
would need some way of creating steam for the mill engine. I decided that I would construct a boiler house. It is probably more elaborate than would have been needed, but I was keen to construct another building from 5mm thick PVC foamboard after the water mill (see How I constructed the water mill).



The size of the building was dictated by the site available beside the sawmill ......

..... and so I made a quick sketch - which is the usual extent of planning for my scratchbuilds.

 The walls

The first job was to mark out the sides for the boiler house on the foamboard (240mm x 140mm).

The size of the windows was dictated by those available from Jackson's Miniatures ( 1/24th scale 10 pane Victorian arch windows - L13). After the horizontal brick courses (at 4mm intervals) had been marked out, and the curved arch brick courses above the windows, ....

..... the vertical brick courses were marked out. I decided the bricks would be 12mm wide which roughly equates to a 3" x 9" brick in 16mm scale. So, divisions were marked at 6mm intervals, so that bricks could alternate on each course. My experience from constructing the water mill showed that it is advisable to mark the brickwork in pencil first, rather than going straight into scoring and embossing as it is so easy to make mistakes - which can be erased more easily when in pencil.

The window apertures were cut out. It didn't matter if the curves were not absolutely accurate as the frames around the windows would hide any imperfections in the cutting-out.

The sides were then cut out ......

 ......and then the horizontal brick courses were scribed and the vertical courses embossed (see below).

 Scribing and embossing

 Scribing the horizontal courses was the easiest of the processes - done with a ruler and a flat-bladed screwdriver. A small amount of pressure was needed to score the foamboard.

The vertical courses were embossed with the 4mm wide blade of the screwdriver. I found that it was easier to put one corner of the blade in the horizontal course, aligned with a vertical course ......

..... and then swivel the blade vertically while applying pressure. 

 Correcting mistakes
Inevitably, when scribing and embossing hundreds of individual bricks, mistakes can happen.

I found that filling the offending indentations with Squadron White Putty.....

which, when dry, was rubbed smooth with a sanding block, and then the correct courses were scribed and embossed.

Once the bricks are painted, these aberrations become unnoticeable.

The windows were test-fitted to check that all was well.

The ends were then marked out (150mm x 230mm), scribed and embossed

NOTE: The slope of the roof was extended 5mm beyond the side edges to allow for the thickness of walls).

The ends of the building were then cut out.

The four sides of the chimney stack were marked out side by side (50mm base, 25mm top, 300mm tall), and then scribed and embossed. Despite my best efforts, slight variations inevitably occurred when scribing the courses and so, marking them out adjacent to each other, helped to ensure that the horizontal courses aligned with each other.

 The four sides were then cut out. As can be seen, two sides were 10mm narrower than the other two sides to ensure the stack was square when glued together.

Three rectangular sections of wall (65mm x 70mm) were cut out on which to mount the chimney stack.

The roof

Foamboard sections for the roof were cut out ( 255mm x 133mm) and then the slates were marked out on 1mm thick plasticard. The slates were drawn in strips 20mm wide. Each slate was 10mm wide and a line drawn across each strip at 12mm to allow for overlap.

Once all the strips had been marked out .......

..... the strips were cut from the sheet ......

..... and the divisions between each slate were cut with scissors. Two snips were made, roughly 1mm apart, though some variation was allowed.

I have found that making only one snip, while being more realistic for closely fitting slates, doesn't sufficiently emphasise the gaps between individual slates.

The upper and lower edges of the roof section were angled (using a craft knife) to enable the two sections to meet at the gable without a gap and to provide an angled surface for the barge boards.

 Lines were drawn across the roof section at 12mm intervals to help ensure the slate rows didn't become crooked as they were glued on.

The first (bottom) row of slates was glued on with superglue.

Then a band of plastic solvent was applied to the 8mm overlap section of the slate strip ......

....... and a band of superglue applied to the next 12mm horizontal strip on on the foamboard roof section.

The next strip of slates was glued on, and the process repeated ........

... until the entire roof section had been covered.

NOTE: The edges were left ragged until the roof sections were glued to the walls (see below).

Assembling the building

The above construction was done whilst I was on holiday (I hate having nothing to do) and so, as we were flying home with nothing but hand luggage (much prefer using baggage allowance and space  for modelling materials than clothes!), I couldn't construct the building until I returned home.

The first job was to assemble the four walls, with reinforcement pieces in the corners.

The chimney was similarly assembled, using medium thickness superglue.

 The roof sections were then glued on, and barge boards made from 8mm wide and 1.5mm thick plasticard glued on.

The barge boards for the gable ends were similarly glued on and then, once dry ........

........ the ragged edges of overhanging slates could be trimmed off.

Any gaps between the walls were filled with Squadron White Putty and smoothed down with a sandpaper block ......

...... and then the brick courses were scribed on to the visible ends of the side walls and any courses filled with filler were tidied back up.

The door

A piece of 1.5mm thick plasticard was cut out to exactly fit into the doorway (110mm x 70mm (rising to 82mm at the apex).

This was scribed with planking at 5mm intervals.

Cambrian Models rivet heads were then glued on where it was assumed bracing would appear on the back of the door .......

....... and the door was then glued into its aperture.

The chimney was glued to its base and attached to the rear of the building .....

...... and 12mm wide ridges made from 1.5mm thick plasticard were glued to the top of the roof.

The boiler house was now ready for painting.


 The first step is to give the walls a wash of cream coloured (or mortar coloured) acrylic paint which is then wiped off with a paper towel to leave the paint in the mortar courses.

 Brick coloured acrylic paint is then dry-brushed over the brickwork.


 Dry-brushing is done by dipping the brush into the paint and then wiping off most of the paint until only a small amount is left on the brush. Then wiping the brush lightly across the surface (diagonally) so the paint is applied only to the raised brickwork. I find a fairly stiff broad brush works best.

 Inevitably, some brick coloured paint will seep into the mortar courses.

This is easily remedied by waiting until the brick colour has dried and then painting mortar colour into the mortar course .........

...... and wiping off the excess with a paper towel.

I finish off by picking out some individual bricks in slightly different shades and tints of the original brick colour to relieve the uniformity of the finished wall.

The slates were painted initially a uniform mid-grey and then individual slates were picked out in slight variations of the grey.

 NOTE: To reduce the gloss finish of acrylic paints, I add a sprinkling of talcum powder. The more you add the more matt the finish.

The woodwork was then painted what I considered to be a suitable 'works' green colour and the top of the chimney stack 'dirtied; with mucky black.


I must admit that of all the techniques I've tried for building construction in the great outdoors (wood, plasticard, concrete), I find PVC foamboard to be the most satisfying material to work with. It's easy to cut, fairly robust, glued together easily and, because it can be scribed, it's really easy to create bespoke brickwork (eg around window openings). I've not yet constructed a building from foamboard which simulates stonework but am tempted to give it a try.

To accompany this building, I am also working on a water tower (see How I constructed a water tower from foamboard - pending). I've decided it will be dual purpose - to supply water to the boiler and also be available for locomotives to replenish their supplies. As Peckforton is mid way between the two termini on the Peckforton Light Railway, it seems appropriate for it to have a water tower for locos.

I need to bed the building into its base on site at the station so, when the water tower is finished, I will position them both.