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Tregonce Cliff, Cornwall

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Name: Tregonce Cliff, Cornwall

Contractor: Harbour Construction

Challenges

atal was approached by the architect for this high prestige project near St Issey, Cornwall at design stage to propose a waterproofing system for a full basement. Requirements for this project were:

  • The system was to achieve a grade 3 environments as defined in BS8102:2009.
  • The basement consisted of a reinforced concrete slab with reinforced concrete retaining walls.
  •  The structure was to be built into shillet rock with the possibility of perched water tables.
  •  Basic radon protection was required.
  • Three warranties were required, design, product and installation, with a 10-year insurance backed option.

Products Used

  • Atal Premsil GMA
  • Atal Flo Board 4e
  • Atal Flo Board 508i
  • Atal Bentofix 5300

Outcome

atal provided a fully warrantied grade 3 waterproofing system on a proposal based around the installation of two waterproofing systems, type A (atal Bentofix 5300) and type C (atal Flo Board 508i with associated sump and pumping system).

 

For the external waterproofing, a type A waterproofing and radon protection was provided using atal Bentofix 5300 under the slab and behind retaining walls.  atal Bentofix 5300 comprises of a 6-mm thick waterproofing membrane consisting of two polypropylene geotextiles (a lower woven fabric and upper non-woven fabric) enclosing powdered sodium bentonite. The outer layer of the non-woven geotextile is impregnated with an additional layer of bentonite. The woven geotextile is coated with a polyolefin layer to provide additional resistance to moisture, radon and methane.
To the inside of the building, a type C waterproofing was provided using atal Flo Board 508iR to both the floor and wall leading to a sump with dual pump system and high level alarm.  Atal Flo Board 508i membrane is a translucent high-density polyethylene (HDPE) sheet with moulded studs at 28 mm centres, for use as part of an internal cavity drainage system.
A maintainable land drain was specified behind retaining walls discharging to soakaways to ensure no hydrostatic pressure came to bear on the structure. Atal Flo Board 4e was installed behind retaining walls to provide protection to both the atal Bentofix 5300 and to the provided drainage behind the retaining walls, allowing backfill with as dug material.
All systems were installed by atal Contracting Limited to provide the client with a 10-year insurance backed installation warranty as required.

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