I am going to make a bold statement that may cause some heated discussion. All pillboxes were made of concrete. Concrete is an incredible building material, first used by the Romans and very much still in use today. As a raw material it can be transported relatively easily; it can be mixed on-site no matter how remote; it can be made even stronger with the use of some inexpensive reinforcement; it can be made underwater; it is incredibly strong when hardened; it can be bulked out with easily obtainable aggregates, and it can be cast or formed into almost any shape the engineer desires.
In this shorter article than usual, I will show you some examples of pillboxes (or hardened field defences as they are also called) and explain the techniques used in their construction. All images are my own; a symptom of being a bit of a concrete nerd.
Table of Contents
Shuttering, also known as formwork, is the term used to describe the casing or mould that concrete is poured into in order to create the desired shape. Concrete can take days or weeks to cure, and this shuttering must remain in place during that time. This section covers pillboxes that have been had this shuttering removed.
Location: Allhallows, Kent (eDOB e04961)
In this first example, I have a Type 24 concrete bulletproof pillbox. It has been cast in situ, using wooden planks as shuttering both inside and out. A three-dimensional mould would have been made from the planks, supported externally by a scaffold of steel or wood, and both internal and external wooden shutters would have been tied together using wire to also stop them from splaying under the weight of the wet concrete. This type of formwork leaves characteristic seams in the concrete where the boards are joined. Where the concrete is very fine, you can even make out the wood grain.
Location: Cuckmere Haven, East Sussex (eDOB e06063)
This distinctive pillbox is a Type 25 Armco variant. So-called because of the American company Armco who manufactured the steel corrugated sheets that formed the form for the casting of these boxes. Some examples still retain their steel sheeting, but I have no evidence to suggest this was part of the original design or if it had not been removed for some other reason.
Location: Buchannan Battery, Orkney (eDOB e07127)
Strictly not a pillbox but I had to include this example of formwork. I can identify three different materials used in the casting of this Battery Observation Post; the distinctive corrugated iron section to the side, but there are also signs of wooden planks being used to form the upper section of the structure, and the bottom section of the rear appears to have been cast using wooden sheets as the formwork. It appears to also have been cast in three distinct phases judging by the visible layers in the concrete; the earlier layers have been allowed to set fully before the pour continued resulting in a non-homogenous wall structure. This is most likely a symptom of the difficulties in sourcing raw materials at the time.
Shuttering (in situ brick and stone)
For a variety of reasons including a lack of materials or construction time, the shuttering may have been left in situ. This can often be misleading to the casual observer as they consider the external material to be the main construction material, but in many cases, this layer was added to facilitate the early removal of the shuttering, or even to avoid using any additional shuttering.
Location: Shanes Park, County Antrim (eDOB e24511)
The red-brick pillbox is probably the one that people first think of when they think of these second world war defences. Rather far from being constructed entirely from red brick, this readily available material is used as a form of shuttering with a core of concrete.
In this example of a Type 24, large precast concrete lintels have been used above the loopholes and door to the rear. Interestingly, the floor of this pillbox has been laid in red brick and not the characteristic concrete as is often seen.
Location: River Medway, Kent (eDOB e05683)
A sorry looking example, this once brick-clad pillbox has been stripped of its bricks leaving the concrete core. The impressions of the bricks can still be seen on the exposed concrete face.
Location: Winchcombe, Gloucestershire (eDOB e11504)
This Type 24 pillbox has been constructed using the best materials for the job and was not rushed. This early was example constructed in August 19401The construction crew left the date of construction written in concrete on the inside. and utilised wooden shuttering on the inside, corrugated iron for the roof, and has a brick anti-ricochet wall on the inside. The outside, however, has been built using local stone laid with concrete. It is likely this external wall was laid first, then the internal shuttering constructed, and the concrete poured. The loopholes would have been cast using their own formwork at the same time as the main pour.
Location: Belfast, County Down (eDOB e24377)
It is the interior roof in this image that I want to draw your attention to. Sheets of corrugated iron have been used as a form when it came to casting the roof, and they have been left in-situ. Slowly rusting and deteriorating in the damp Northern Irish climate.
I have not seen corrugated iron used very often for casting the roof of pillboxes, but the same technique was also employed in the anti-tank gunnery range buildings near the Giants Causeway. Perhaps the same contractors of Royal Engineers constructed both sites.
Shuttering (precast panels)
A specific type of shuttering was also employed and left in place, and that is utilising precast concrete panels. None of the examples I have seen has utilised panels specifically constructed for the purpose. The examples below appear to have used general construction materials that may have been improvised for the purpose of concrete shuttering.
Location: Arlingham, Gloucestershire (eDOB e02988)
A variant of a Type 26 pillbox, there are four to the west of Arlingham in Gloucestershire that appear to have been constructed using a combination of precast concrete panels and conventional wooden shuttering. The panels, used on the external walls, internal walls and the interior roof are similar in design to the wall sections of prefabricated garages; but their use in this instance is as shuttering for a central core of concrete.
They are very similar in construction to an example in Aylesford, Kent (eDOB e02992).
Location: Newtownards, County Down (eDOB e24506)
The shuttering inside and out on this pillbox is precast concrete panels that appear to be paving slabs. The concrete seams around the top and edges of the pillbox suggest traditional shuttering was also used, or even to a limited extent to encase the slabs during the pour. They would have been difficult to hold in place if the walls were cast in one pour, so perhaps the concrete was poured level-by-level as there is no evidence of any tying being used to secure the slabs to the structure.
The pillbox (eDOB e24754) on the hill between Donaghadee and Millisle has also been constructed using this method.
Location: Buchannan Battery, Flotta (eDOB e07127)
Not technically a pillbox, but I had to include a second example from Buchanan Battery on Flotta. On a much larger scale than the pillboxes above, this three-level battery observation post has been cast using large precast concrete panels laid horizontally as shuttering.
Precast pillboxes and components
By precasting items in factories or production lines, it was possible to both reduce the costs and time associated with constructing a pillbox. There were some compromises when precasting a whole pillbox; the size and weight of each unit had to be such that it could be transported and then installed using available machinery. As a result, there was only really one type of precast pillbox widely used. However, precasting was employed to great effect in manufacturing components for pillbox construction.
Location: Lywara, Hoy (eDOB e03030)
Arguably the only real precast concrete pillbox of the war; the Norcon provided light protection from small arms to the occupants. Supplementary protection would have been provided from sandbags or earth banks against the sides.
It is not to be confused with the 1980 Yarnold Sangar which can still be seen around the perimeter of many Cold War airforce sites.
Location: Lympne, Kent (eDOB 28928)
A retractable concrete turret designed for airfield defence, the Pickett-Hamilton fort was constructed from two precast concrete pipes; one sitting inside a larger, set into the ground. The top of the pillbox was flush with the ground until manually raised using a hydraulic jack by the crew inside. In this example, the steel reinforcing framework can be seen. The roof of the pillbox would have also protruded around the circumference but has since been damaged. Entry and exit of the pillbox were through a roof hatch, and internal space to work and operate weapons was very limited.
Location: Detling, Kent (eDOB e09875)
This is a fine example of a precast loophole in a Type 27 octagonal pillbox with a central anti-aircraft mount. The pillbox itself is brick-clad, and one of a ring of defences protecting RAF Detling in Kent.
Location: Bangor Golf Club, County Down (eDOB e24755)
Not quite a precast loophole, but this rather off-centre example has been constructed using what appears to be a precast concrete window sill as the lintel, and a precast paving slab to support the bottom of the recess that would have accommodated a machine gun tripod leg. Judging by the not-so-crisp lines on the concrete used as the bottom of the loophole, this may have been cast in-situ during the construction of the pillbox.
Location: Pett Level, East Sussex (eDOB e03952)
I found this pillbox by chance while on a hike along the coast a few years ago. On first inspection, it appears to be a standard Type 24 constructed with concrete block, similar to breeze blocks. Upon closer inspection, the blocks appear to be have been precast, including what must be bespoke corner blocks angled specifically for this design of pillbox. The aggregate in the concrete appears to be beach gravel which may have been collected locally from the nearby beach.
A lime mortar has been used to bond the block together which has eroded out of the top few courses of brick, and the calcium can be seen staining the outside of the pillbox.
If these blocks are indeed precast it has a lot of similarities to the Christchurch Block Sangar developed in the mid-1980s.
Prefabricated pillboxes, that is those that were constructed in kit form, only existed in my knowledge in one form; a Type 26 design manufactured by the Stent Pre-cast Concrete Limited.2A new type of pillbox, Dr William Ward, the Pillbox Study Group All components of this pillbox were precast by Stent and were deployed in kit form for construction on site.
Location: Pirbright, Surrey (eDOB e23440)
A truly prefabricated kit pillbox, manufactured by the Stent Company, this pillbox could be erected on site relatively quickly using slotted upright beams and precast concrete panels bolted together and then filled with concrete. Precast loopholes were also supplied that extended between the inner and outer walls.
And finally, there are always one or two that don’t fit in any other category.
Location: Winchcombe, Gloucestershire (eDOB e28027)
Possibly one of a kind, this sandbag pillbox is similar to a circular Type 25, but has been made with concrete-filled hessian sacks that would have laid dry, and as the concrete was wetted it would have set.
This variant is very similar to Beehive-type pillboxes found around Northumberland but appears to be smaller.
Location: Signal Hill Battery, Gibraltar
When I first wrote this article I thought the sandbag pillbox above would be the most unique in terms of construction methods. That’s before I visited Gibraltar and came across this beauty on Signal Hill, one of the highest points on the Rock. The external walls have been made from blocks of concrete (cement and aggregate) cast into old petrol cans. The steel of the can was left in place, and each block has also been mortared into place.
The exact use of this pillbox is uncertain; the loopholes have been placed lower down than would normally be expected, and the location high up on the rock would only really be effective for weapons with a high angle of depression. Perhaps the large concrete mantels above the loopholes are to accommodate a steep angle permitting weapons to fire down the hill. I didn’t get the opportunity to look inside when I visited.
You can view a high-resolution version of each photograph used in this article on Flickr.
- 1The construction crew left the date of construction written in concrete on the inside.
- 2A new type of pillbox, Dr William Ward, the Pillbox Study Group