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Basement & Cellar Conversions, Tanking


Most families yearn for extra space as an inbuilt requirement in today’s modern world. Generally the initial reaction is to think of moving to a bigger and generally far more expensive home, with the built in stress and heartache that such a move brings.

You could always extend your home to provide more space internally, but ultimately lose space externally from your garden.

Stop; there is a growing band of homeowners that are utilizing the space they already have, by converting dank and dingy cellars and basements into bright and cosy additional rooms instead.

Maybe you are after a TV or cinema room, games or play room, home office or study, gym, utility room, or music room for example.

Whatever you desire Sovereign has the expertise and experience to help achieve your goal.

Is It Worth It?

Basement conversions are often the preferred option of achieving valuable additional living space as opposed to upsizing to a bigger, more expensive house.

Practically, for your average household, converting your cellar or basement can add as much if not more space to your home as extending upwards into the loft, or going out over the garden.

Most people think about creating extra space, but also about long term added value, both of which are results from converting your basement.

Some people simply think that getting that much needed extra space without all the downsides associated with moving house, is what matters.

So, basement conversion – is it worth it? In any event the answer is yes, but first consult the people that know and will help; the specialists at Sovereign.

Be Practical

One of the most important factors with any cellar or basement project is making sure the damp- proofing/waterproofing is correct.

Structural waterproofing below ground level is a specialised operation and should be carried out by professionals having the right level of understanding and experience.

Sovereign specialise in damp-proofing and structural waterproofing and can provide the necessary knowledge and expertise required for your basement conversion.

Standards to Meet

When considering converting your basement and the importance of waterproofing it correctly, it is important that all concerned must be conversant with BS8102:2009 Code of Practice for protection of below ground structures against water from the ground.

As a Code of Practice, this British Standard takes the form of guidance and recommendations. It recommends that, during the design process and at all stages of the construction process, the designers, specialists, manufacturers/suppliers and installing contractors establish and maintain effective channels of communication. Regular and clear communications coupled with good site supervision allows variations and amendments to the design to be planned and executed without compromising the performance of the waterproofed structure.

To this end Sovereign lead the way with their successful long established and unrivalled specification service, whereby upon request an individual specification will be drawn up, for any waterproofing job, however big or small. Furthermore, this service, being an integral aspect of any basement conversion, is provided free of charge by the people that know.

Contact the specialists at Sovereign now.

Waterproofing Systems

Substructure waterproofing guidance and recommendations is given in BS8102:2009, Code of Practice for protection of below ground structures against water from the ground.

This Code categorises forms of waterproofing into one of three types, being:

Type A (barrier) protection – which is dependent on a separate barrier system applied to the structure, and this is often referred to as “tanking”. It involves the application of an appropriate waterproofing barrier to the walls, base slab and where relevant, the roof of a below ground structure, such that the envelope of the structure below ground is protected against water ingress.

The Sovereign Hey’di K11 Tanking System will provide Type A Protection in accordance with BS8102.

Type B (structurally integral) protection – which is provided by the structure itself.

Type C (drained) protection – which is provided by the incorporation of an appropriate internal water management system. It involves the use of a dimpled, flexible, high density polymer sheet membrane which is placed against the internal face of a structure and is designed to intercept water penetrating the structure, and directing any water ingress to a suitable drainage facility, of which this system is wholly reliant.

The Sovereign Cavity Drainage Membrane System will provide Type C protection in accordance with BS8102.

For assistance and more details please contact the specialists at Sovereign.

Planning Permission

The planning regime covering the creation of living space in basements is evolving and under review.

Converting an existing residential cellar or basement into a living space is in most cases unlikely to require planning permission as long as it is not a separate unit or unless the usage is significantly changed or a lightwell is added, which alters the external appearance of the property.

Where a basement will adhere to the existing layout and not extend beyond the original footprint, then planning permission may not be required.

Excavating to create a new basement involving major works, a new separate unit of accommodation and/or altering the external appearance of the house, such as the addition of a lightwell, or indeed excavating and underpinning an existing void, will require planning permission.

Where the building is listed and/or in a conservation area then consent is likely for internal or external work.

In all circumstances we would advise that your Local Planning Department is consulted as works should not commence until all appropriate consent/approvals are received.

Building Regulations

Building Regulations do apply to basement conversions.

These cover areas such as fire escape routes, ventilation, ceiling height, waterproofing, electrical wiring and water supplies for example.

Underpinning and foundation works may also be needed and relevant.

The Party Wall Act 1996 must also be considered where other properties are adjoining and walls are shared or possibly even when a neighbouring property is in close proximity.

For further assistance contact the specialists at Sovereign.

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  1. 10 SHEETS DRAMEXLATH 304 #SS 2500MM x 700MM (PACK 10)

    10 SHEETS DRAMEXLATH 304 #SS 2500MM x 700MM (PACK 10)

    2500mm x 700mm Stainless Steel Lath available in packs of 10 sheets. Learn More


    Designed to run the pump in the event of mains power failure. The unit is continually trickle charged Learn More
  3. BRUSH


    Block brush used for the application of K11 Tanking slurry. Learn More
  4. COB PLUGS 10MM x 90MM PACK 200

    COB PLUGS 10MM x 90MM PACK 200

    Cob plugs are designed for use in substrates where a good fixing point is hard to acheive therefore Learn More


    A solvent free two-part resin system that rapidly cures chemically to form a vapour proof surface membrane. Learn More


    Sovereign Fast Fix Board adhesive is a rapid new way of installing dry lining systems for both new build and refurbishment work Learn More


    A deep penetrating liquid that renders soluble salts in salt-affected masonry insoluble, thereby preventing the passage of hygroscopic salts from the substrate into any new mineral coating that is applied such as Hey'di K11 tanking or cement render. Learn More
    Size: 10K, 5K
    Starting from...
    Price From: £65.97 £65.97 (+VAT)



    A hydrophobic powdered mortar gauged with water and normally used for wall/floor and wall/wall junction fillets as part of the Hey'di Tanking System. Learn More


    Nitrile gloves that provide excellent protection from both chemicals and cementitious powders. Learn More


    Sovereign SBR Bonding Agent is a dispersion polymer of carboxylated styrene butadiene copolymer. It has been extensively used in the building industry for many years in the modification of cementitious systems, such as mortars, render, screeds, for example. Learn More
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Need any further information or advice about any of Sovereign product range?

Please contact us by following the link below and a member of our team will respond shortly to any questions you may have.

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