A diagnostic survey will identify the prevalent factors, and Siteseal will recommend the optimum solution based on the intended use of the basement. If the existing structure is largely sound or to be built (new), a cementitious tanking approach would usually be suggested, should an existing basement be in a poor condition, cavity drainage using a studded membrane and a pump to drain the water would be preferable. Localised problems would most likely be treated with resin injection.
Waterproofing new and existing basements
New basement methods:
Cementitious (renders and slurries)
Cavity drain Sheet membrane
Existing basement methods:
- Cementitious (renders and slurries)
- Cavity drain
- Leak sealing by resin injection (for localised repairs)
- Sheet membrane
Cavity Drain Membrane Systems
Cavity drain membranes work on the principal of allowing water to continue to penetrate the structure but control it in the air gap and divert it to a suitable drainage point or pump (if required). Cavity membranes do not allow pressure to build up against the internal construction, and the air gap behind the membrane allows the structure to 'breathe' and dry out. The membranes are impermeable to water, and gas and water vapour, thus protecting the basement internal space from dampness. Membranes are loose laid on floors and fixed to walls using special plugs and sealing materials.
Cavity membranes can be fitted with little or no preparation to the substrate. Once fitted, wall surfaces can be dry lined or plastered directly, and floors can be screeded, or a suitable oard system installed. This method of basement waterproofing allows decoration and floor finishes to be completed almost immediately, without long drying out periods.
These systems are a specialist waterproofing multi-coat render, or a multi-coat cementitious slurry that can withstand the external water pressure present in a basement. Once installed, a cementitious render system will maintain a dry environment by creating a physical barrier preventing water entering the basement area.
Cementitious coatings can be applied direct to the substrate, but they do require preparatory works to ensure that a good key is available to bond the materials to. Multicoat render applications can be installed with several interim coats increased to reflect the degrees of water pressure resistance required.
For the sealing of construction joints, expansion joints, connection joints, or cracks and fissures on concrete and masonry, a Hypalon Strip bonded with an epoxy resin is used to provide a high joint movement capacity.
Concrete and Structural Repairs
Concrete repairs can greatly extend the life of buildings and car parks. Once the cause of the decay has been identified, with hammer testing, visual survey, carbonation test, chloride test and cover meter test (this records the depth of steel reinforcement below concrete and provides a "low cover" warning). Typical concrete problems are caused by low cover to the reinforcement, carbonation of the concrete and/or high chloride levels.
Solutions include the reinstatement of defective concrete and the application of protective Anti-Carbonation coatings which slows the loss of alkalinity to the concrete whilst some coatings can regenerate the concrete and stop decay.
The methods available for repairing concrete may be divided into the following groups:
- Hand applied mortars
- Sprayed concrete and mortar
- Re-casting with concrete
- Flowable grouts and concrete
- Electro-chemical processes
- Corrosion inhibitors
- Filling and injection of cracks
- Sacrificial anodes
Condensation has become a serious issue in recent years with greater levels of insulation incorporated in new build housing both raising the average ambient temperature and reducing the exchange of air with the outside. Siteseal supply and fit a range of room ventilators which are energy efficient, quiet and effective.
Condensation is caused by water being deposited on cool surfaces with black mould growth then growing in the areas of dampness. In more extreme cases pooling of water can appear on floors, sills and furniture.
The problem of condensation and mould growth often occurs at low levels where the surface of the wall is coolest, often starting in a corner and travelling along the length of the wall. This spread of damp can often be confused with rising damp and householders frequently find it hard to believe that condensation can cause such severe damp problems.
Siteseal will undertake a comprehensive survey covering timbers and walls to determine the nature and cause of dampness, enabling us to recommend the optimum solution. A diagnostic survey will identify the prevalent factors and take into account the causes of water ingress whether due to chemical erosion, building defects, poor maintenance or simply the absence of any damp proofing measures. Damp Proofing is purely about replacing or installing a barrier to prevent moisture rising by capillary reaction in a structure. Damp Proof Courses (DPC) are designed to protect internal timbers below and above ground level.
Rising Damp & Damp Proofing
Rising damp can occur for various reasons - the failure of an existing damp proof course (DPC), bridging due to the raising of external ground or internal floor levels, or in older buildings, the complete absence of a damp proof course. Rising damp is unhealthy, unsightly and can lead to timber decay and heat loss. Brick, stone and mortar are porous allowing damp from the ground to rise by capillary action, carrying with it ground salts including chlorides and nitrates. Salts left by rising damp can absorb moisture from the atmosphere leading to wall dampness in conditions of high relative humidity, whilst the cyclical nature of crystallisation and rewetting can ruin decorations and break down internal plaster.
Current methods of damp proofing include the following.
Utilising a concentrated, thixotropic silane / silicone cream to form a barrier against rising damp. As the cream slowly diffuses, it releases a silane vapour which reacts with the silica in the masonry to form a water repellent resin.
The gravity-fed transfusion units allow a slow, even distribution of the siliconate fluid into the wall and to form a damp proof barrier, but unlike pressure injection, there is no wastage via hidden fissures or voids.
This method is sometimes recommended, primarily for 112mm single brick walls. The fluid is injected into the wall with single lance under low pressure to form the barrier against rising damp.
This method is a two coat, cold applied damp proof membrane, which dries to a uniform gloss black finish. It is typically used as a tanking membrane in accordance with BS8102:1990, damp proof membrane to ground floors and as a vapour barrier behind cladding and plaster. It can also be used and an effective barrier to Radon Gas.
Tanking is defined as a waterproof membrane applied over a surface, preventing completely the entry of liquid water under hydrostatic (water) pressure. External tanking is usually undertaken using a sheet membrane system although various options are available. The waterproofing of retaining walls on single-sided basements, sloping sites or step changes in modular floor construction are amongst the most common works undertaken by Siteseal.
The current Building Regulations and BS 8102:1990 (Protection of structures from ground water), stress the importance of, where possible,
(i) maintaining the continuity of the waterproofing system,
(ii) avoiding breaking the integrity of the waterproofing with wall ties and
(iii) the desirability of cross flow ventilation.
The optimum remedy will depend on a host of factors such as, age of the building (existing buildings only), proximity to any water courses or ground water, the level of waterborne contaminants, condition of the existing masonry or brickwork and nature of the water ingress.
External Coatings: Applied to the to external face of brick, stone or concrete structures these work by lining the pores of the masonry rather than blocking them - allowing the wall to continue to breathe, whilst preventing water ingress.
The most common structures to require waterproofing are car parks and podium slabs either as standalone elements or those incorporated as part of a building or wider development. A number of solutions are offered depending upon the usage levels, size and any local influences, these range from the latest rapid drying, anti-skid resin coatings to High density polyethylene profiled sheets.
Siteseal's range of solutions can enhance the visual appearance and improve the efficient usage of car parks by using various colours to demarcate different zones for parking and no-parking, visitors, delivery, private parking, refuge collection etc.
Timber decay has usually been caused by dry rot or another wood-destroying fungus such as one of the wet rots. Affected timbers should be removed and replaced with pre-treated timber, whilst any remaining timbers at risk of being affected by the rot should be treated with an effective fungicide. Where rot has passed through the masonry, it should be isolated using physical containment and/or masonry sterilisation.
Timber can become damp for a number of reasons although among the most common causes are leaking washing machines, shower trays, baths or condensation. The dampness can also come from outside the building, for example, leaking roofs, rising dampness or dampness penetrating through walls.
Woodworm holes found in timber are caused by the larvae of beetles that feed on the timber. Larger holes on the surface of the timber are formed when the adult beetle emerges from the timber to mate. There are a number of species of woodworm, and the precise method of treatment will depend on which species is attacking the timber.
Wall Ties and Fixings
Structural repairs can take various forms; from masonry / render and concrete stitching through the installation of steel reinforcing bars, to the replacement of wall ties be that in the form of mechanical or resin based systems.
Siteseal are an approved contractor for Thor Helical ® the leading manufacturer of Precision Engineered Helical Bars, Wall Ties and Fixings.