Waterproofing an Insulating Concrete Framework (ICF) new build basement

HomeWaterproofing an Insulating Concrete Framework (ICF) new build basementWaterproofing an Insulating Concrete Framework (ICF) new build basement

ICF System

This system uses large interlocking polystyrene blocks that form a house shaped mould.  Each block is form of two pieces of insulation jointed together by a metal strap.  Once the blocks are all attached they create an inner and outer wall of insulation with a gap the middle.  Concrete is then poured into the gap to form the walls of the ICF house.

The team have completed the waterproofing work on this ICF new build basement in Derbyshire. Our client required us to design and install a waterproofing system with a warranty. 

The waterproofing solution we used is defined in BS8102: 2009 Protection of Structures against Water from the Ground as a “Grade 3” environment where no dampness is permitted. 


Combined Waterproofing System

  • Type A: Barrier Protection – external waterproofing
  • Type C: Drained Protection – internal waterproofing

Major third part warranty providers such as NHBC, Premier Guarantees and LABC have insisted for some time on the installation of combined protection as a fundamental condition of their warranty. They also require that a CSSW qualified waterproofing design specialist be involved at the design stage.


Installation of Type A Barrier Protection System – External Waterproofing

First Visit

Once the builders had erected the internal and external walls incorporating a land drain away from the property the Damptec team could begin work.

We installed Delta Dual Proof pre-applied water proofing membrane prior to the concrete slab being poured over the formwork system.  This is a fully and permanently bonded composite sheet that not only waterproofs but protects against gases and chemicals. Suitable substrate: concrete blinding, compact hard-core and compact sand.


Second Visit

Primary resistance of the structure is provided by Koster bitumen-based waterproofing on the positive side.

  • We applied two coats of Koster Deuxan-2C polymer modified thick bitumen compound at 6kg/m². The second coat was applied following the installation of the glass fibre mesh.


  • Once the Deuxan had cured we mechanically fixed Delta-GeoDrain Quattro membrane, with joints overlapped and sealed.


  • We then applied 2 coats of NB 4000 for continuity between the Type A and the cavity tray (DPC) as shown in green in the pictures before curing.


Installation of Type C (Drained) Protection – Internal Waterproofing

This is secondary protection, which manages any water ingress which occurs as a consequence of an installation defect in the external membrane, and is provided by a cavity drain membrane system:


Gravity drainage was installed in a pre-cast chase formed in the concrete.

Wall Membrane

We installed 8mm cavity drain membrane to all walls with specialist fixings. For this purpose a sealed plug was used.

All joints where flanged sections were located were sealed with waterseal tape. Where studded sections meet, waterseal rope will be used.

Floor Membrane

We installed a 20mm floor membrane joined to the wall membrane using compression tape. 


Previous Project

Former Baldwin’s Omega site,Sheffield

Next Project

Combined Waterproofing System – Type A (Barrier) Protection and Type C: Drained Protection

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