However, depending on the extent of the damp and the nature of your property, you may require a more extensive solution such as a pump-operated drainage system. As always, we recommend that you talk to a specialist company to find out what kind of cellar tanking is right for you. If your London home suffers from cellar damp, call London Damp Company on Our basement tanking specialist will conduct a free survey to assess the problem in your cellar and find the best way of treating it.
Whatever your damp problem, we have an effective solution. Skip to content. London Damp Company. SW17 7BE Call It is applied directly to damp walls. When the tanking slurry cures, it forms an impermeable waterproof barrier, preventing water ingress and damp. The most effective way of tanking your basement or cellar is with tanking slurry. You may sometimes see this referred to as cementitious tanking.
Both names refer to the same product - a specially formulated mixture designed to be applied to cellar walls to stop water ingress. It either comes pre-mixed or as a powder to mixed on site with clean water.
Some people may recommend tanking a cellar with a bitumen coating, but this method is not suitable for tanking an entire cellar or basement. Bitumen coatings are more suitable for smaller above ground areas and external waterproofing. Tanking slurries are a special blend of Portland cements, aggregates and chemical modifiers that work together to block the passage of water.
Our PermaSEAL tanking slurry contains an additional acrylic polymer that improves strength, bonding and abrasion resistance. When it comes to tanking wet or damp walls, you need to prepare thoroughly before applying the tanking slurry. There are several steps you should take to minimise the risk of the tanking failing. You need to prepare the masonry surfaces thoroughly.
In older homes, this can take a long time but preparation is key to a watertight system and well worth the effort. The first job is to ensure that you can get to the full surface of all the walls removing all shelves and other items and that the floor is also clear. You then need to hack off any plaster and render from the cellar walls along with any previous coatings bitumen, paints etc right back to the original masonry.
Rake out any old mortar joints and any other loose material before finally making sure the walls are dust free. If there are or have previously been issues with high levels of salts, it is recommended that you apply a Salt Inhibitor to the cellar walls to prevent any salts from compromising your tanking. Note: For tanking to work, the brickwork needs to be stable so that it can cope with the build up of water pressure.
If this is in doubt, then you will need to take action to ensure the walls can resist water pressure. Once you have removed all materials from the walls, you need to check if there is active water seeping from the wall. If there is evidence of water seepage, you will need to tap off this water pressure where necessary. When tanking a cellar, we always suggest that the walls and floor are coated to create a waterproof box. The point where the wall and floor join can be a potential weak point in any system, we therefore recommend creating a reinforced joint.
At the wall floor joint, chase out the floor to a minimum of 20mm x 20mm cutting into the wall if possible. Flush out the chase and remove any debris. Whilst this is still damp, apply one coat of tanking slurry mm up the wall and mm across the floor. Whilst the slurry is still tacky, apply PermaSEAL Fillet Seal over the tanking slurry and into the chase creating a cove from the wall to the floor.
Make sure you keep your skin covered and wear gloves, a facemask and goggles before mixing the tanking product. Tanking slurry is alkaline in its powder form therefore you need to avoid contact with skin or eyes and avoid inhalation of the powder. Most tanking slurries come as a powder and require mixing on site. Only mix enough tanking that can be used within 30 minutes as the product will become unworkable and will have to be disposed of. You should start by adding the required quantity of clean water to a suitable mixing vessel.
Slowly add the powder to the water whilst continuously mixing. We recommend mechanical mixing at a slow speed with a high torque drill and a plaster mixer.
Mixing should be continued for three minutes after all the powder has been added to the mixing water to obtain a batter-like consistency. Allow the material to stand for one minute before remixing and then applying.
Cellar tanking products are designed for application onto damp substrates. If your cellar walls are relatively dry you should wet out the substrate fully with clean water, making sure it is damp but with no standing or surface water before applying the tanking. Such methods of keeping habitable, below ground spaces dry, certainly date from the Georgian period, although there may be earlier examples.
Water which appears on retaining walls or floors today may come from the exterior, due to penetrating or rising damp and in some cases through leaking land drains or sewers, streams, and a fluctuating water table.
But it may also be the result of condensation or leaks from internal services. All possibilities need to be considered. When first built, most below ground structures were fit-for-purpose, with floors and ceilings that were fairly level and walls that were close to vertical.
Otherwise they would not have survived, often for many hundreds of years. It must also be the case that when such lower level spaces were first built they would have been generally usable and relatively dry, if only by the standards of the day. A cellar built without any damp-proofing will always be slightly damp when compared with a modern tanked alternative. Thus any problems that we find on site today are likely to be the result of a change in circumstance from that position, and we need to ask the simple question: what might have changed?
To answer this we need to look for evidence on site:. Once you have established how the sub-floor space has been constructed and have tried to assess the cause of the fault which may take several visits and even opening-up works , then a decision can be made on how to address the problem.
The real problem with tanking is that unless it is carried out to the exterior of the fabric, the damp remains in situ. Furthermore, a membrane applied to the inner face relies on its adhesion alone to resist water pressure. Excessive water pressure can damage or lead to leaking of the membrane material, and any timber such as window frames, lintels, floor joists, skirtings and architraves all need to be wrapped or isolated from the remaining damp source to prevent an outbreak of wet or dry rot.
Behind skirtings and other joinery, dry rot can progress un-noticed causing extensive damage, and must be prevented. To be effective, the membrane has to run continuously under floors and up walls which will often require floors to be reduced and re-laid if head room is limited. Internal walls and other structures rising from the floor will also have to be incorporated in the tanking strategy, either by isolating them from damp sources usually the floor and the retaining walls or by tanking them, too.
It must be appreciated that the cost of this type of work can be expensive. The use of membranes either in conjunction with drainage systems or as part of a full tanking system can be quite effective if properly thought through, allowing lower level accommodation to be successfully reused. This said, trying to achieve 21st-century standards of water-tightness in an 18th-century cellar perhaps misses the point. This article is reproduced from The Building Conservation Directory , Over the past 30 years he has surveyed all types of property throughout the UK from 13th century halls and 17th century manor houses to late 19th and early 20th century shops, railway stations and civic buildings.
Damp and decay. Damp and decay treatment non-destructive. Damp and decay treatment products. Environmental control. Site Map. Damp below Ground Geoff Maybank A vaulted cellar of a Georgian terraced house in Bath: the cellar has been successfully adapted to provide a useful extension to the kitchen.
A typical Georgian terrace in Bath: the area provides light and access to the kitchen on the lower ground floor, and cellars extend under the pavement on the right. DEFECTS Water which appears on retaining walls or floors today may come from the exterior, due to penetrating or rising damp and in some cases through leaking land drains or sewers, streams, and a fluctuating water table.
To answer this we need to look for evidence on site: How is the cellar or basement constructed?
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