Basement Conversions in Berkshire, Hampshire, Surrey & Oxfordshire
Biocraft carries out a range of basement conversion and basement waterproofing services throughout Berkshire, Hampshire, Surrey and Oxfordshire.
To arrange a basement conversion survey or for advice on converting a basement or cellar please call 0800 781 8358.
Converting damp basements in Berkshire, Hampshire, Surrey and Oxfordshire
Damp cellars and wet basements can be converted to dry useable living spaces using a tanking or cavity membrane basement waterproofing system.

Basement conversion in Sonning Berkshire. All underpinning, Waterproofing and Finishing works by Biocraft Ltd
Basement conversions can add significant useable space to your home. A professional basement conversion can be used as an office, a playroom, a bedroom, a basement studio, an extra bathroom or a home theatre. A basement conversion can add up to 30% floor space to your home and will add value to your home (130-175% of the basement conversion project cost).
Biocraft is a member of the British Structural Waterproofing Association (BSWA) and the Structural Waterproofing group of the Property Care Association. As a basement conversion specialist we can offer 10 year insured guarantees through Guarantee Protection Insurance (GPI) Ltd, which is required for new build basement home warranties. Biocraft ltd is a member of the Federation of Master Builders (FMB) and Constructionline.
Biocraft carries out a range of basement conversion and basement waterproofing services throughout Berkshire, Hampshire, Surrey and Oxfordshire.
To arrange a basement conversion site visit or for advice on converting a basement or cellar please call 0800 781 8358.
Basement waterproofing in Berkshire, Hampshire, Surrey and Oxfordshire
Damp cellars and wet basements can be converted to dry useable living spaces using a tanking or cavity membrane basement waterproofing system.
Basement conversions can add significant useable space to your home. A professional basement conversion can be used as an office, a playroom, a bedroom, a basement studio, an extra bathroom or a home theatre. A basement conversion can add up to 30% floor space to your home and will add value to your home (130-175% of the basement conversion project cost).
Biocraft is a member of the British Structural Waterproofing Association (BSWA) and the Structural Waterproofing group of the Property Care Association. As a basement conversion specialist we can offer 20 year insured guarantees through Guarantee Protection Insurance (GPI) Ltd, which is required for new build basement home warranties.
Design of Basement Conversions
Biocraft designs its basement conversion solutions in accordance with BS8102:2009, the code of practice for protection of structures against water from the ground.
Basement conversions – A basement before conversion and waterproofing. This split level basement was excavated to increase headroom and three basement lightwells were added to provide natural light to the basement area.
Basement conversions – The basement following conversion, Basement lightwells added, basement floor level reduced, basement waterproofed with cavity membrane, and split level basement finished as kitchen and dining room.
A properly designed and installed waterproofing system for your basement conversion will provide you with significant additional living space and add value to your property. Please click on one of the basement conversion case studies below:
Biocraft Case Study Bladon lodge
Why convert a basement?
Basements have traditionally been an under utilised part of residential and commercial properties. This is because basements were originally built for storage, and had no form of waterproofing, resulting in a basement area being damp, dark and unsuitable for modern living. A full size basement can account for up to a third of the available floor space in a building but are often only used for storage of items that are not affected by damp conditions.
Many basements have be converted over the last twenty years however poor design and/or workmanship means that they have failed, leading to damp penetration and unacceptable living conditions. The image below shows an example of a failed tanking system
Biocraft specialises in the conversion or upgrading of residential and commercial basements using cavity drain membrane or proprietary cementitous tanking systems. Designed in accordance with BS8102, our basement conversions solutions are guaranteed to provide you with a dry space whatever your intended use. Converting your basement can provide a substantial amount of additional dry living space and considerably increase the value and utility of a property.
Cost of basement conversions?
A first floor, two bedroom apartment in Sunningdale valued at £420,000, was revalued at £540,000 following the conversion of a full sized basement, which added another large bedroom, a study, a shower room and a wine cellar. The cost of the conversion was £75,000.
A mid terrace property with an unconverted 1/2 size basement in Reading had an £35k basement improvement project, which added ~£85k to the value of the property, together with the addition of ~25% extra floor space.
Your damp basement can become a workshop, a playroom, a den, a home cinema, an office, a studio, an archive room, an extra bedroom or even an apartment with kitchen and bathroom. You decide what you want and Biocraft will do the rest.
The cost of a basement conversion depends on the size of the basement, the need to increase headroom, the requirement for underpinning, the requirement to reroute services (water, gas, sewer etc) and the finish that is required. Basement conversions can range from £10k to over £250k, but always represent value for money due to the increase in property value and the addition of living space.
Basement conversions & working to BS8102
BS8102 (2009) Code of practice for protection of structures against water from the ground is the basis for basement design, and contains guidance on environmental grades, height of water tables, drainage and other information that is used to ensure that a basement waterproofing system will function correctly.
When you contact Biocraft in relation to a basement conversion project, a qualified surveyor will determine the construction of your basement and which waterproofing solution would be appropriate. The structure of the building will be examined together with the ground conditions and surrounding area. Based on your intended use and required performance level, a design will be prepared in accordance with BS8102 and a report and quotation prepared.
Environmental grades and intended use
Table 2 of BS8102 defines grades of waterproofing that can be used to design waterproofing systems. Most domestic and commercial applications are grade 3.
CD membrane for basement conversions
Cavity Drain membranes such as the Isola Platon “System Platon” are made of high-density studded polyethylene sheets, which are impervious to water and are vapour proof. When placed against structures the studs form permanent cavities between the structure and the internal shell. They can be used internally or externally to drain and control water & damp ingress. (Click here to see the components of a cavity membrane system.)
“System Platon” is not a tanking system. The term “Tanking” originates from the industrial process of lining structures with a waterproof material, which were applied either externally (on the positive side) or internally (on the negative side). Tanking materials such as multi-coat renders, cementitious waterproofing slurries, asphalt’s and liquid applied bitumen coatings, to name but a few rely on either a mechanical or chemical bond directly on to the substrate and work by holding water back. The majority of which are vapour permeable.
Walls in the majority of circumstances are not engineered to withstand the bending stresses applied when a negative pressure barrier tanking system is used to hold back water pressure. Brick is very strong in compression but weak in tension.
Traditionally in the United Kingdom cementitious tanking systems are applied to below ground structures, but if the structure was to be subjected to hydrostatic water pressure, the resulting bending stresses are often far to great for the barrier system to cope with and therefore de-bonding or cracking, resulting in failure, will occur. The installation of Platon membrane doesn’t change the status quo and therefore Platon Cavity membranes are ideally the most suitable and economical method of providing an effective and long lasting waterproofing system that is also sympathetic towards building structures and for those seeking maximum assurance ‘System Platon’ is considered to be the most trouble free.
Advantages of cavity drain membrane
One of the main advantages of Platon Cavity Drain membranes over cementitious systems is that they do not stop water at the point of entry, so hydrostatic pressure is not increased any more than it would be without a waterproofing system.
Because the status quo is not altered, stresses are not induced in the substrate other than those, which would be induced anyway. For this reason, it is often possible to retain substrates, which would have to be replaced when using a cementitious system, and yet still comply with BS8102.
Cementitious Tanking Systems
Cementitious coatings are premixed compounds comprising cement, graded aggregates and chemical additives. They are applied by brush or trowel to form a waterproof coating 1-3mm in thickness.
They can be applied directly to sound suitable substrates or to a sand/cement render basecoat which has been applied to a properly prepared and sound substrate.
Cementitious coatings have little structural integrity of their own and rely on the integrity and structure of the substrate to which it is applied. Since tanking systems do not remove water from the structure, the system may be subject to hydrostatic pressure (Designing to BS8102, assumes that the structure will be subject to a head of water during its life). If the structure is not capable of dealing with the loads and stresses induce by hydrostatic pressure it will fail.
Biocraft carries out basement waterproofing and basement conversions throughout Berkshire, Oxfordshire, Hampshire, and Surrey. For advice or to arrange a site visit please call 0800 781 8358 or email [email protected]