22 Aug 2014
In May 2014 SMHS were contacted by a national newspaper about a remarkable story from a homeowner in Storrington. He had been digging out an old ornamental pond in his back garden when his spade suddenly disappeared into a void. Further excavation revealed an underground air raid shelter!
At the invitation of the owner, SMHS undertook a one-day survey and minor excavation of the structure in August.
We quickly confirmed the structure as an air raid shelter. A brick entrance with concrete steps took us below ground level and into the shelter proper. A socket for a wooden door frame was evident in the floor; the door itself had long gone.
The floor here was about 1 metre below normal ground level, and an earth mound had been thrown up on top of the shelter for added protection.
The internal structure was clearly based on the Government Anderson shelter, designed for a small family. A low brick wall supported a metal piping framework, with corrugated iron bent over it. The iron itself is laid horizontally, as opposed to the rolled vertical iron sheets of the Anderson.
It appears that the shelter was covered in concrete as an added protection against bomb splinters. This might be because the corrugated iron used was the thin, domestic type and not the thicker sheeting used for the Anderson.
The construction had been of good quality and using good quality materials too; this lead us to estimate that it had been built before the national cement shortage of summer 1940.
The influence of the Anderson shelter design is interesting; the elaborate structure can only be a privately-commissioned shelter built to a higher standard than the Government issue type.
The interior was relatively clean and so all that was required was a brush down to remove excess dust and cobwebs.
Actual excavation was necessary on the exterior, however. The brick entrance surround had suffered some damage (possibly when the pond was built) and was buried. A morning's work exposed the brickwork.
A trench was opened up on top of the earth mound at the end of the shelter furthest from the entrance. At this end was a ventilation pipe which was blocked with compacted soil. A length of scrap water pipe hammered heavily down the pipe finally cleared the obstruction.
As the shelter had been covered in concrete, measuring the height of the pipe from inside to the top, and then from the top down to the concrete would allow us to estimate the thickness of the roof.
The excavation revealed all sorts of pipework associated with the water pump system from the pond. After digging about 50cm deep, the concrete roof was uncovered. The ventilation pipe was measured and the thickness of the concrete estimated to be 14cm.
An interesting facet of the concrete in the roof, steps and shelter floor was its colour, a pinkish tint. This was possibly due to brick dust in the mix.
Once the excavations had been completed and the site cleaned up, a full measuring survey was carried out. This didn't take too long, as the structure was a relatively simple one.
A scale plan was drawn and a 3D model (shown below) was constructed using the data. Some of the detail (such as the foundation) is speculative in the absence of full excavation. The brickwork around the entrance that has been removed is reinstated, again according to our best interpretation.
The graphic below places our structure alongside an Anderson shelter. The similarity between the latter and the shelter proper at Storrington cannot be coincidence.
The Anderson's internal space is a few inches larger, but the Storrington shelter has a few key advantages over the design that influenced it.
|Min. earth cover||38cm||51cm|
|Distance from house||1.98m-4.57m||7.3m|
|Cost||Free (means tested)||?|
The table at right compares an Anderson built 'out of the box'; according to the minimum specifications of protection as described in the assembly instructions.
One advantage the Anderson holds is the presence of an emergency exit should the entrance become blocked by a collapsed house. One of the back wall panels could be released from inside, the earth then excavated into the shelter to allow exit.
The other card the Anderson holds is that of cost; it was issued free to those families who could least afford to pay, with a means test to determine the cost for those who were better off. The Storrington shelter, on the other hand, was probably quite an expensive investment.
But what does this expense buy in terms of protection? The Storrington shelter is sunk marginally below the recommended minimum depth of the Anderson, but has a concrete covering and a greater amount of earth on top, thereby enhancing protection. (The Anderson could, of course be sunk deeper and have a greater depth of soil on top.)
The Anderson was supposed to be erected with the doorway facing the house to provide an element of protection against blast entering the shelter. However, more than 15ft (4.6m) away from the house and it was recommended that a blast wall be constructed out of earth or other material.
The Storrington shelter is probably outside of the greatest danger area of the house collapsing on it, but no blast wall would be required as the shelter compartment is not only underground, but is perpendicular to any blast effect coming down the stairwell. The probability of the entrance being blocked by debris is minimal, and the concrete covering rules out an emergency exit of the type used in the Anderson. The only debris likely to affect the shelter is that of the shelter itself, in which case a direct hit would likely prove fatal to the occupants anyway.
Aside from added protection, the Storrington shelter represents significant potential for greater comfort over the Anderson. The latter had no issued door; it was left to the householder to improvise a solution. Andersons were draughty, cold and very often, damp. Some local authorities did encase the footings of Andersons in concrete to prevent the flooding problem that deterred many people from using them.
The interior of the Storrington shelter, while showing evidence of moisture penetration over the years did not seem to have flooded, despite having a pond built around it after the war! A drainage duct at the foot of the stairs would reduce the amount of rainwater getting into the shelter.
The presence of the ventilation pipe would probably allow some sort of stove to be incorporated, taking the edge of any damp and cold inside.
The door at the foot of the stairs would also keep draughts out and be easy to black-out. The door also potentially assists in defeating another weapon of war - poison gas. With the door sealed and the ventilation pipe blocked up, the occupants might be able to survive without having to wear stuffy, exhausting gas masks - as long as there was sufficient air in the shelter for the number of shelterers. At worst, the occupants could don their gas masks and unseal the door if the air inside became too stale.
From our survey it appears that the structure at Storrington was constructed 1939-40 as an air raid shelter. Part of the shelter was closely based on the design and specifications of the Government-issue Anderson Shelter.
Comparison with the minimal construction of Anderson Shelter highlights the advantages of the Storrington example, both in terms of enhanced protection and comfort for the occupants. It is noted that the cold and damp Anderson shelters were often avoided; the Storrington design helps to offset some of these drawbacks. In all, this structure is an interesting and unusual combination of official Government design combined with a privately-funded air raid shelter.
Sussex Military History Society works alongside other heritage organisations, and our final report on this excavation and survey will be submitted for inclusion in the West Sussex Historic Environment Record.
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