We don't like dampness in walls!
A capillary water barrier based on synthetic resin/rubber

Renovation of Moisture Damaged Masonary Walls

            2.5.4) Synthetic Elastomeric Resin Procedure

1. Causes, Analysis

Damp walls and wet basements can be a nightmare for any building owner. A specialist contractor using suitable detection equipment is required for timely detection, as inspection simply by feel or visual appearance does not indicate the full extent of moisture migration.

Renovation of existing structures (or of new structures not incorporating a proper sealing system) can involve complex problems that must be assessed and defined by damage analysis. This analysis should determine:

  • the direction of moisture migration, i.e. whether upward or lateral,
  • for buildings with substructures, if ground water or stratum water is leaking from soil into the masonry,
  • if moisture within the masonry is caused by attainment of the dew point (i.e. condensate formation) and
  • if hygroscopic salts in the masonry are causing moisture attraction.

Moisture damage can result in destruction of mineral construction materials, mortar decay, cracking and dislodging of rendering, plaster and paint, salt depositing, increased heating costs, bothersome odours, impaired living conditions and even health hazards for occupants due to fungus growth.

Walls which have not been waterproofed allow absorption and transport of water through capillary passages. This water often contains harmful water-soluble salts leached from the soil that can damage the structure. These salts are generally nitrates, sulphates and/or chlorides (the mixture commonly referred to as saltpeter). Their hygroscopic nature, i.e. ability to attract and hold air humidity and moisture, aggravates the situation.

In periods of dry weather, this absorbed water can evaporate, leaving the salts behind. In subsequent periods of rain or high humidity, the salts attract large quantities of water (only 8 g of salt are required to bind 1 litre of water by hydration), bringing back the problem.

In buildings without basements, damp walls are frequently caused by a nonexistant or defective horizontal moisture barrier, allowing moisture conduction upwards by capillary action through the mineral construction materials in the structure. A new horizontal moisture barrier is required in such cases. If saltpeter has deposited on the wall and ceiling surfaces, the rendering or wall plaster affected must be replaced.

In many older buildings with basements, lateral moisture ingresss is encountered as well. In such cases, the outer masonry surface must be uncovered and sealed by appropriate means (e.g. bitumenous or elastic coating materials) including a protective backfill layer.

All money and effort expended in renovation can be for naught if state-of-the-art technology and engineering practice for prevention of moisture migration are not followed. The knowhow and experience of a specialist contractor are essential for complete damage analysis and design of a truly effective renovation programme.
Replacement of the existing masonry, including a layer of bitumenised felt, plastic membrane or metal sheeting within the new masonry, provides a safe solution of the problem if properly carried out. This renovation method however can frequently cause cracking damage due to differential settling and is very costly. In addition, the rooms or building sec-tions involved cannot be used during the procedure.

2.2 Insertion of Steel Sheeting
Insertion of steel sheeting is a repair method with limited applications. This method can be used only on masonry walls incorporating a continuous horizontal joint; also the horizontal seal created is above floor level. Additional flanking measures are required. The masonry is subjected to severe physical stress by the insertion process. Here again, cracking due to differential settling can be encountered.
Various qualities of steel sheet can be used (in accordance with the corrosion protection required) ranging from simple chromium steel to stainless grades.

2.3 Saw-Through Procedure
In this procedure the masonry is sawed through completely, allowing installation of sealing sheet. The masonry is then fixed in place by wedges and the void spaces are pressure-grouted. The procedure can cause cracking due to differantial settling if not carried out properly. Even when properly conducted, the saw-through procedure is timeconsuming and expensive. Here as well, additional flanking measures are required. Widia chain saws can be used only on masonry with a continuous horizontal joint. For quarrystone or other irregular masonry (mixed masonry), diamond saws are required.
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2.4 Electro-Osmotic Procedures
Electro-osmotic procedures require extensive, costly preliminary studies prior to execution including analysis of the salts and masonry type involved, and as well determination of the presence of any electric cables, water lines, or other metal objects in or near the wall, any of which rules out the use of electro-osmotic procedures except for certain limited applications. Electro-osmotic procedures do not prevent moisture ingress as such but instead constantly remove the moisture in the wall. The process is electrically powered and thus is subject to interruption in the event of power failures, etc.
Various injection procedures are employed. They differ greatly in the compositions of the materials used.

2.5.2 Silicification Procedures
Water glass compounds and silicification agents are only able to penetrate masonry with low moisture content. The density of these materials is greater than 1.0 g/l. These materials are water-soluble, water-dilutable and thus limited in their diffusion capability. The reaction time of water glass mixtures is typically extremely short.

At below-freezing temperatures these materials cannot be processed due to low permeation rates and possible damage to the structure if freezing. The injection boreholes are relatively large (approx. 28mm in diameter). Silicification of quarrystone, ventilated brick, honeycomb brick, etc. is not advisable as their void spaces would have to be filled with cement emulsion compounds prior to injection. In some cases the masonry may require prewetting with a lime solution.

In addition these materials tend to become brittle on solidification: vibration or settlement can cause hairline cracks, again permitting upward moisture migration. Depending on the chemical composition of the salts in the masonry, heavy surface depositing can be encountered.
2.5.3 Synthetic Resin Injection
2.5.4 Synthetic Elastomeric Resin Procedure

Injection of nontoxic synthetic elastomeric compounds with aromatic-free solvents provides a number of significant advantages. Their low density (less than 0.9 kg/l) ensures excellent permeation performance in even the smallest capillary passages, even at masonry moisture levels of over 50%.

Sealing by synthetic elastomeric compounds can be used for quarrystone walls, ventilated brick, honeycomb brick, hollow block brick, etc. Void space filling is not required as the reaction does not begin until 6-10 weeks after injection (depending on temperature and moisture content) and the material is drawn from the void spaces into the masonry.
The synthetic elastomeric materials are made up of a combination of various components such as impregnating agents, synthetic resins, natural resins and synthetic oils. Their balanced chemical composition makes them resistant to acids and alkalines, nitrates, sulphates, chlorides, etc. and as well to oxidation, biological attack, UV radiation and below-freezing temperatures. They are thus fully suited for use in areas with salty ground water (i.e. coastal regions).
This material provides further advantages: it allows air permeation in spite of the hydrophobisation, does not promote condensate formation and is not prone to embrittlement, retaining full elasticity in the capillaries (i.e. vibrations and similar stress types will not cause formation of new hairline cracks).
Complete saturation (impregnation) is ensured when the recommended amounts are used. The simple gravity-feed injection process does not interrupt use of the building and does not entail structural alteration. The small diameter (16 mm) of the injection boreholes ensures that static properties of the structure are not adversely affected.
This simple, easy-to-install system provides a long-lasting horizontal seal which sets industry standards for state-of-the-art technology.
NOTE: The dampness present in the wall dries out gradually following renovation. This drying-out period lasts approx. one month per 1–1.5 cm of wall thickness for all of the renovation methods described here.