HydraDry Tanking Slurry

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HydraDry Tanking Slurry

Wykamol Group | Basement Tanking

Basement Tanking & Internal Waterproofing Penetrating Damp


HydraDry is a cementitious Tanking Slurry designed for application to the internal surfaces of walls and the associated solid floors of cellars, basements and other areas below ground level and subject to penetrating dampness.

The HydraDRY system prevents ingress of liquid water and works by forming a physical and chemical bond with the substrate. It provides a monolithic waterproof membrane yet still allows some vapour transmission thereby reducing the risk of condensation.

HydraDRY can provide sufficient protection of a ‘Grade 3’ basement as defined in Table 1 of BS8102:2009 and conforms with Category 7 of the BCA Basement Waterproofing Design and site guides.

 HydraDRY is supported by BBA Certification Certificate No: 02/3961.

Available in 20Kg bags (Inside a mixing bucket). 

  • BBA Approved

  • Waterproofs cellars and basements.

  • Suitable for brick, stone, block, concrete, etc.

  • Resists hydrostatic pressure up to 5 metres head

  • Can be applied to saturated surfaces

  • Easy brush application

  • Suitable for use in contact with potable water


Health & Safety Recommendations:

Take the usual labour hygiene into account.

PPE should be worn during application. See our Safety & PPE Products.

Consult label and material safety data sheet for more information.


It is essential that preparation of the surfaces to be tanked is carried out to a very high standard to ensure that a good physical key is obtained. All fixtures, fittings (e.g. timber wall plugs),plaster or other wall coverings should be removed.

It is strongly recommended that grit blasting is used to prepare the wall surface although where major contamination is present needle guns or “comb” hacking systems (resulting in a rough-textured finish) can be used.

Where necessary defective brickwork should be replaced and poor mortar joints repaired. If the substrate is irregular, e.g. random stone construction, a 3:1 sand / cement scratch coat should be applied to provide a sound, even base prior to the application of HydraDRY.

It is important that good quality sharp, washed sand is used; a waterproofing additive may be included provided the application of HydraDRY is commenced within 48 hours.

N.B. It is essential to determine the suitability of the substrate to accept a cement based coating. All traces of any gypsum-based materials must be completely removed. Where it is known or suspected that high levels of salt contamination i.e. sulphates, nitrates are present in the substrate, mortar joints should be deeply raked out and an SBR-sulphate resisting cement primer and re-pointing mix used prior to the application of HydraDRY. Where the building structure has cracked and / or is subject to subsidence, it should be established whether the movement of ground is still active.

HydraDRY is a relatively rigid material and is not recommended where movement is likely (e.g. under roads, pavements etc.)

Where active water leaks are present it must be established that the structure is capable of taking the increased load which may result from waterproofing work. Alternatively, take measures to reduce the water table. If a few minor leaks exist these should be cut out to leave a square hole in the substrate.The holes can then be filled using Water-Stop Plugging Compound mixed to stiff putty. It is important that Water-Stop is pushed firmly into the hole to ensure that it is totally filled. If severe leaks are experienced pressure vents should be formed by following a similar procedure, but incorporating hollow pipes into the holes, fixed using Water-Stop.

The water can be drained into buckets or directly into the drainage system. HydraDRY is then applied in the normal manner. When the HydraDRY system has cured each vent is carefully removed and the hole plugged with Water-Stop prior to the application of two coats of HydraDRY.

Wall / floor and corner joints usually need special preparation to avoid sharp changes of angle in the tanking membrane.

The joints should be thoroughly raked out, cleaned and wetted prior to application of a Fillet Seal or an SBR / Cement Primer and SBR modified 3:1 sand / cement fillet.

The HydraDRY membrane should be applied the full height of any soil retaining structures and at least 150mm beyond the damp-proof course (if a chemical DPC is being installed this should be a water-based or injection mortar-type system and the HydraDRY applied before DPC reduced suction).

In free-standing basement walls it may be possible to install a horizontal DPC to control capacity moisture movement at or just above floor level, but only if the resting water table height is never above floor level. Similarly, vertical DPC’s (set back approx. 500mm) may be installed in such walls to ‘isolate’ them from soil retaining structures as long as HydraDRY is applied a full 100mm back from the wall / wall joint.

Alternatively, if any doubt exists concerning water table heights, all walls and floors in basements should be tanked.

Where external ground level is above basement ceiling level and of solid masonry construction it will be necessary to treat the ceiling with HydraDRY. Wooden ceilings with joists bearing on walls to be treated with HydraDRY should be isolated and reformed and/or other measures taken to protect the timbers from decay (further advice available on request).

In the majority of tanking operations it is preferable to replace existing concrete floors with a new floor incorporating a damp-proof membrane.

However, if the floor is known to be structurally sound and the surface in good mechanical condition it is possible to use HydraDRY as a DPM followed by the application of a suitable screed.

However, vapour impermeable or moisture sensitive floor coverings such as vinyls or timber flooring should be avoided unless a physical DPM complying with CP102 is used.


Ensure powder is stored at room temperature for a minimum 12 hours prior to use.

During application the temperature of both the substrate and materials must not fall below 5°C.

In winter months avoid using chilled mixing water. Use warm water (20°C) for HydraDRY and Water-Stop.


Immediately prior to application of HydraDRY or backing coats the substrate to be treated should be cleared of all dust etc. and thoroughly wetted with clean water. At the time of application all surfaces must be damp but free of surface water.

HydraDRY powder should be mixed with clean water to a brushable slurry paste consistency (approx. 5.2 litres / 20kg HydraDRY powder). Mixed material should be used within 30 minutes.

HydraDRY should be applied using a stiff bristled brush or broom (wash frequently to avoid clogging). Two coats of HydraDRY should be applied at a thickness of 1.5mm per coat. It is essential that the first coat is brushed well into the surface to ensure a good bond with the substrate. The second coat may be applied as soon as the initial application has dried sufficiently to form a firm base. This will normally be between 2-16 hours depending upon site conditions (allow more time for curing then temperatures fall below 10°C).

Where HydraDRY is applied by towel (reduce gauging water slightly) this must be restricted to the second coat and a “stippled” finish left (use applicator brush) to provide a physical key for subsequent re-plastering.

HydraDRY should not be applied in a thickness greater than 3-4mm (2 coats). Where each application cannot be finished within a single working day it is essential than an overlap of at least 250mm is used to prevent butt joints.

Work should not be stopped at corners or other natural breaks in the construction.


If the basement has a known history of aggressive salts specific precaution should be taken to deal with these (the type of salts present should be determined by analysis).

In particular HydraDRY is not suitable for use in areas of high sulphate content (where the sulphate content exceeds Class 3 limits of BRE deposit 363.) It may be possible to impart improved salt resistance to HydraDRY by incorporating an SBR Bonding Agent into the gauging liquid (i.e. 1:1 with water). In other situations an SBR Primer / SBR Render based on sulphate resisting cement may be advisable.

In very severe cases of poor wall stability or acute salting conditions consideration should be given to alternative strategies for achieving a dry wall / floor surface.


When a new floor is being laid, the physical membrane should be cut off at the top of the slab and the procedure noted under wall / floor joint followed prior to the laying of the final screed.

Wall / Floor & Corner Joints:

Detailing at the wall floor joint must be carried out to a high standard. Fillet Seal is a cementitous mix designed specifically for the task.

Alternatively two coats of an SBR primer bonding coat are applied (1 part SBR : 2 parts cement by volume).

As soon as possible thereafter a 3:1 sand / cement mix incorporating a good quality sharp washed sand and gauged with SBR : Water (1:1) is used to form a fillet at least 50mm high and 50mm deep at the wall / floor joint.

The fillet is trowel applied taking care not to pierce the SBR primer coat. The edges of the fillet should be 'feathered' to give a smooth curved appearance (this may be achieved by using a glass bottle).

As soon as the fillet has set firm the application of HydraDRY should proceed (if the SBR modified fillet fully cures a fresh coat of bonding primer will be necessary to re-key the surface).

Where the HydraDRY is not being used over the whole floor area it must extend a minimum 250mm across the floor (the second coat should stop 50mm back from the first). If a sandwich bitumen membrane is being incorporated this may be applied directly to the HydraDRY and screeded in the normal manner.

Bitumen emulsions are unsuitable for these situations.

N.B. If the wall / floor joint is a source of active water leaks cut a square-shaped chase (not a v-notch) at the base of the wall and fill with Water-Stop before proceeding.


Approximately 3kg per square metre per coat (two coats recommended).



Re-plastering is an integral part of the tanking specification, protects HydraDRY from impact damage and reduces the incidence of condensation.

Renovating Plaster is particularly recommended as a means to avoid cold surfaces but a sand : cement plaster incorporating RenderProof Waterproofer may also be used.

Re-plastering should be carried out in accordance with BS5492:1990 and the appropriate Replastering Specification Data Sheet as soon as the final HydraDRY coat has set to form a firm base (12-48 hours). If the HydraDRY is left longer prior to re-plastering an SBR-modified cement slurry may be required to overcome low suction in the substrate.

N.B.Gypsum based plasters must not be used in direct contact with HydraDRY.

Use only stainless steel metal angle beads to form details on external corners etc. (use SBR-modified mortar to fix). In hot weather keep the plaster / tanking moist (e.g. mist spraying, polythene sheet) over the first 48-72 hours to encourage full curing and strength development.


The success of any tanking system depends upon the integrity of the system being maintained. Therefore, conventional fixing methods, i.e. screws etc. cannot be used and alternative fixing methods have to be employed.

For lightweight fixings it is suggested that adhesives are used to stick items such as skirting boards, electrical conduit etc. A wide range of products are available for this purpose, e.g. polyurethane mastic’s.

For heavy duty fixing points, before application of HydraDRY, oversized holes should be drilled. These can then be plugged with Water-Stop and a plastic insert.

For major fixings a larger size hole should be prepared, i.e. a half brick and the same basic procedure followed.

In exceptional circumstances heavy duty fixings may be made after the completion of the HydraDRY system by using chemical anchor systems. i.e. epoxy mortars, two-pack resin systems, but this is not recommended.


On completion of the HydraDRY system it is important that the system is allowed to dry out naturally without the use of radiant or fan heaters, dehumidifiers or forced ventilation (convector heaters to provide temperatures above 10°C may be acceptable).

Once the surface is substantially dry, paint or other finishes may be applied, it is essential that all decoration is vapour permeable and it is suggested that an emulsion paint is used.

In tanked basements the provision of adequate background heating and ventilation is essential to ensure condensation risks are controlled.

Data Sheets

Technical Data Sheet

Safety Data Sheet

BBA Certificate

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£28.25 ex. VAT | £33.90 inc. VAT

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