Subterranea Britannica

Harpenden Air Raid Shelters

Harpenden
Herts
OS Grid Ref: TL 133144
Location: Harpenden
Date of visit: November 2014

[Source: Chris Rayner]

Harpenden has an impressive collection of surviving town centre air raid shelters. All four shelters are underground trench shelters; one is at Bowers Parade, two at Leyton Green (South and North), and one at Queens Road.

Inside, the shelters were all precast concrete lined, with sloping concrete floors, which partly accounts for their dryness apart from some mud washed in above the stairs.

Shelter layouts varied. Bowers Parade is the largest with six legs in a crenelated layout, while the two Leyton Greens have U-shapes with three legs, and Queens Park has four legs in a square. These patterns are all common variants, the lengths of the legs dictated by the need to protect shelterers in adjacent sections from the deadly effects of blast in the event of a direct hit.

Each of the shelters was accessed by two staircases, one at each end, making the Leyton Green shelters the quickest to fill and Bowers Paradeís the slowest. Itís likely that there were above ground walls or enclosures which were removed after the war.

The upper sections of walls still had some of their original coating of whitewash, applied partly for cleanliness and also to accentuate the limited electric lighting present, and the cut-off point showed how high bench backs might have extended.

Council records indicate a similar date for both Bowers Parade and the Leyton Green shelters, with permission being granted in July and the beginning of August 1939.

Queens Road appears to have been earlier, having been planned in 1938, approved in March 1939 and completed in August of that year. It is though the only one which had bunks, which were added in December 1940 once it was clear that the Luftwaffe had switched to night raids. Another unusual aspect with Queens Road is that it is furthest away from nearby houses.

Shelter capacities are given as c. 180 for Bower Parade and c. 100 for each of the Leyton Green shelters, based on benches on both sides. Figures for Queens Road are given as 400, although c. 120 seated is said to have been more likely, while bunks would have reduced this further.

Greater capacities might have been possible though, as shelter passage legs were often based on a maximum of 50 people per section to protect shelterers in adjacent legs from blast in the event of one section having a direct hit. In this case, shelter capacities might have been of the order of c.300 for Bower Parade, c. 150 for each of the Leyton Green shelters, and c.200 originally (pre-bunks) for Queens Road.

The construction details seen were similar to many trench shelters, with precast concrete panels being generally used for walls and roof linings. Ceilings are generally flat although the panels that house the emergency exist are tilted for an unknown reason.

Insitu concrete was used on occasion to extend wall lengths beyond the precast panel module size, to deal with junctions for which there was no standard precast panel, and was also used for the shelter floors and entrance stairs. Brickwork was used for the stair walls and for extending escape hatches up to the surface.

The floors were laid to falls towards the entrances and this coupled with the continuous edge channels and the floor gullies near entrances appears to be responsible for the dry conditions experienced. Laying falls towards the entrances was good practice for dealing with flooding and washing down. Perimeter channels are helpful in dealing with condensation and minor leaks, which are directed from the roof to the walls and then removed by the edge channels.

The concrete condition appears reasonable considering its age and location and in comparison to other shelters seen. In some sections the concrete cover on the walls in particular has spalled off revealing the steel reinforcement behind, but such areas are very localised.

A surprising feature is the absence of gas curtain frames, which is unusual given their age. It is likely that the Council relied on shelterers to bring and use their gas masks in the event of a gas attack..

Chemical toilets, none of which remain present, would have been located in pairs in prepared recesses by the entrance steps at Bowers Parade and Leyton Green to provide some ventilation, while at Queens Road they are at the junction of two shelter passages while the stairs enter mid-passage. Queens Roadís toilet provision is also at a lower ratio of fitting to occupant, though the change from benches to bunks would have improve their ratio. The separation of the two cubicles was by a very thin structural terracotta block partition, one of which survives ta Bowers Parade.

Although no benches or bunks remain, the steel upstand plates to which they would have been connected are still present, and a number of fixing bolts are scattered on the passage floors, including a small pile in Leyton Green South. The bench fixing plates occur at regular intervals in pairs (i.e. on opposing sides of the shelter) and appear to be connected by an upstand, possibly a T-section. The assembly may have been bolted to the concrete floor or connected to cast-in lugs. The steel upstand crossing the floor has been covered by what looks like a cement screed finish, which at the same time forms the perimeter drainage gullies. This is an unusual approach and may have been an afterthought to address both seating and condensation drainage.

In Queens Roadís shelter the floor plate upstands are again paired but the screed is only on one side and lacks a perimeter channel. The pairing might date back to time it had benches, while the screed variation suggests that it may have added at a later date. A section near the main entrance stairs appears to have partly collapsed revealing a shallow hollow core. One problem with this theory though is that the connecting bar linking the fixing upstands would be a substantial trip hazard if not at least partly covered by screed.

Power for lighting appears to enter the shelters through the toilet recess rear wall which may have been panelled off originally. Sections of the steel distribution conduit remain in parts of the shelters.

The shelters appear to have been unheated as there are no flue holes, nor are there any signs of mechanical ventilation having been provided.

Wartime graffiti though was sadly very limited, apart from several pencil-drawn numerals seen in the first two shelters visited, which may have been bay identification numbers, and a childís sketch of Hitlerís face found in Leyton Green South.

Access was allowed by Harpenden Town Council with the Kent Underground Research Group assisting with shelter access and air quality monitoring

An earlier survey is available via the Archaeological Data Service.

[Source: Chris Rayner]

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Last updated 11 November 2015

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