Below ground waterproofing for new build farmhouse

Below ground waterproofing for new build farmhouse

Landmarks (UK) Ltd, a Yorkshire based developer of exclusive, sustainable properties, has used Triton waterproofing systems in the construction of a traditional two storey farmhouse.

The property sits on a natural gentle slope, so the basement is fully buried to the rear with a raised patio area to the front. The design incorporated a secure underground garage, workshop, garden store and wine cellar.

The property was built using ICF (insulated concrete formwork) where polystyrene forms are used to contain the wet concrete when casting in-situ concrete walls – and are left in place. The end result is a very strong, air-tight solid wall that offers “u” values ranging from 0.24 – 0.11 W/m²K. When the concrete is placed in the polystyrene, it dries out very slowly, and is not affected by thermal movement. It creates an ideal environment for waterproof concrete.

The lower slab was made waterproof by the installation of a membrane beneath it and the inclusion of Triton’s TT Admix in the mix. TT Admix contains active chemicals that react with fresh concrete to generate a non-soluble crystalline formation that seals the concrete itself against the penetration of water or liquid.

Triton’s TT Waterstop, a pre-formed water bar which swells up to 350% when in contact with water, was placed into all joints. When TT Waterstop is fully encapsulated by poured concrete, the expansive forces form a seal against the concrete surfaces to resist hydrostatic pressure and to stop water from entering the sub-structures. The shuttering around the slab had made provision for the concrete groove in the face of slab and the TT Waterstop was fixed into the groove using Triton’s TT Swell Mastic expansion sealant. TT Swell Mastic swells up to 100% when in contact with water, and has long lasting adhesive and hydro-swelling properties. TT Waterstop was also placed in the centre of the wall on top of the slab so that the joint between the wall and the slab was protected.

Triton TT Admix was incorporated in the concrete mix used to form the basement walls. The walls were filled in one day, with over 60m³ of concrete being pumped and compacted.

All joints between the polystyrene panels were protected with a width of Triton Fleeceband reinforcing fabric to give extra tensile strength. (The Fleeceband was bedded in to a priming coat of TT Vapour Membrane). The external toe of the concrete slab had Triton Fillet Seal, trowelled into a wedge shape to make sure any flowing water flowed away from the joint. This joint was also protected with Triton Fleeceband.

Externally the basement walls were treated with two coats of Triton TT Vapour Membrane, a ready blended, single component acrylic modified coating, that provided the primary waterproof and gas proof barrier. Platon Double Drain, a membrane which, in this application, provides a drainage and protection layer, as well as working as a traditional cavity drain membrane which allows air movement between its face and the formwork, was then draped down the walls to connect to the land drain that had been constructed at the bottom of a French drain around the rear and sides of the building. This drains into a watercourse on the low side of the building. The geotextile layer of the Platon Double Drain membrane is extended over the land drain to ensure that fines are kept out of the system.

The external walls were then back filled, maintaining a divide between the 20mm dust free gravel of the French drain and the soil backfill by using sheets of plywood, which were gradually lifted with the digger as filling took place. The back fill was compacted using a steel wheeled vibrator.

Jon Rowlands, a director at Landmarks UK Ltd, explained that although his company is steeped with traditional skills, they are actively seeking and using modern methods of construction to build energy efficient housing with low maintenance and low running costs. He said “We use Triton products because they are ideally suited to our Nudura ICF system and they have a long and respected history in the trade.”

“For example, the TT Admix is self-healing which is essential for use with ICF because each web that ties the polystyrene panels together is a potential leakage point. The panels are strong enough to withstand a poker when full of wet concrete, so we don’t have issues with voids, but if there is capillary action along the webs, then the self-healing properties of the TT Admix are able to deal with this scenario. The high density polystyrene is also an ideal base for the application of TT Vapour Membrane because the two products bond together naturally.”

He explained “ICF works at its best when dry, so that full use can be made of the insulating characteristics of the product. This is why we use Platon Double Drain and TT Vapour Membrane to keep water away from entering the fabric of the building. Using TT Admix in the concrete is the safety back up system because if there is a problem this can be repaired from within the building relatively easily.”

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Triton Systems

Triton Systems

Triton Systems is an established supplier of all types of structural waterproofing (Types A, B and C as defined in BS 8102 2009). Key systems include BBA approved TT Admix, used widely in the construction of watertight concrete structures such as...
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