The 258 mock Tudor flats of the Hanger Hill Garden Estate were built between 1935 and 1938 in  mock Tudor style  during a transition period in the use of building materials for domestic construction (houses and flats) in the UK.

For example the waste water gullies were constructed of concrete, bricks and clay drain pipes which would no longer be acceptable under current (2026) Building Regulations- as these materials are prone to cracking during hoy dry summers when the local London clay soil shrinks.

Internally the floors of ground floor flats are are made of suspended timber planks with the plank timber floor suspended on wooden joists around 30 – 60 cm above ground level. At ground level the earth may or may not be covered with a thin layer of oversite cement. It is important to realize that the oversite cement is not waterproof and does not act as a damp proof membrane. Thus if the local water table reaches the the surface during heavy rain  or winter flooding there will be times  when there is water flowing directly under the timber floor of many HHGE ground floor flats.

During the original construction  in the 1930s, surface water drains were provided to ensure that excess water was soon dispersed away from the site, but most of these drains are now cracked, blocked, or broken.

Despite the damp ground beneath many HHGE ground floor flats these  1930’s flats were not necessarily damp to live in because the open fireplaces and chimneys in each room allowed a constant flow of air though the flat, ensuring excellent ventilation.

FAST FORWARD TO 2026:

  • Most HHGE flat owners  have blocked their chimneys and installed central heating.
  • The soakaways  design to disperse  rainwater into the lawns are all silted up.
  • The gullies designed to remove grey water are cracked and broken.
  • The soil pipes and sewers designed to remove soil waste  are cracked and blocked by tree roots.
  • A large amount of water is flowing into the earth underneath the wooden floor of the flat.
  • Many ground floor HHGE flats are suffering from mold and condensation.
  • The HHGE Block managers are unable to cope with the volume of complaints they are receiving.

 If the flat is a ground floor flat then the air warmed by the central heating will pull the damp air  up from the damp earth under the floor of the flat  and without any ventilation  the damp air will stay in the flat causing black mold and condensation inside the flat. See this diagram.

If all the grey water from 3 flats is leaking  from a broken gully into the soil below the flat then the mold and evidence of damp inside the flat can become extreme.