What system should I use?

Do I Need Waterproofing or Damp Proofing?

Water ingress and damp penetration can cause serious problems in a building. If you suspect that your property is suffering from any water-related issues, the first thing to do is identify the problem. Whether you need waterproofing or damp proofing will affect the approach to solving your problem. Here’s how to determine which solution is right for you.

Consider the External Ground Levels

Problems can occur if dampness is showing in a property with external ground levels that are higher than the internal floor level. In this scenario, the moisture residing in the external ground is a contributing factor to the dampness already identified. The high ground could also be saturated enough for water to bear against the structure, creating a risk of water ingress.

Where high ground levels exist, it should be assumed that water ingress is a possibility. Therefore, a waterproofing system is required. Conversely, where there are no high ground levels, a damp proofing solution is required.

Summary:

Low External Ground Levels: If the external ground levels are lower than the internal walls (or if the external ground could be lowered), a damp proofing system is the recommended solution.
High External Ground Levels: If the external ground levels are higher than the internal walls, for example, in a basement or cellar, a full waterproofing system is required.

Technical Details

British Standards

When the external ground is higher than the internal floor, and waterproofing is required, the recommendations within the British Standard 8102:2022 (Code of Practice for The Protection of Structures Against Water Ingress) should be followed.

BS 8102:2022 is a design document used to inform the designer of the various methods of waterproofing available and to assist in the correct specification of those systems.

Grades of Waterproofing

The general principles for successful waterproofing involve deciding on the end-use of the space to be waterproofed. Depending on the desired end-use, BS 8102:2022 defines three Grades of internal environment. These are the levels of waterproofing protection required for each:

Grade 1a: Seepage and damp areas from internal and external sources are tolerable, where this does not impact the proposed use of the below-ground structure.
Grade 1b: No seepage. Damp areas from internal and external sources are tolerable.
Grade 2: No seepage is acceptable. Damp areas as a result of internal air moisture/condensation are tolerable; measures might be required to manage water vapor/condensation.
Grade 3: No water ingress or damp areas is acceptable. Ventilation, dehumidification, or air conditioning is necessary; appropriate to the intended use.

Once the internal Grade has been established, it is important to select a waterproofing system that is capable of achieving the required environment. This assessment is based on both the type of structure involved and the type(s) of waterproofing being used. The purpose is to give specifiers an accurate understanding of the potential success of different specifications and builds. It also helps guide them through the myriad of different waterproofing products and combinations available in the market. Visually, this assessment is represented as an NWI (Newton Waterproofing Index) ‘score’ that can be used to judge each waterproofing specification.

A Word of Caution

With the above in mind, a word of warning is necessary. It is common for people to question why they should have a full waterproofing system if they only have slightly high ground levels and/or there is no running water present at the time. While we understand their reticence, if any aspect of the structure is below ground, then BS 8102:2022 is still relevant.

It states that a risk assessment should be carried out, determining the long-term water pressures, the effects of surface water infiltration, and the use of external drainage and cut-off walls. The risk assessment should also consider the potential effects of climate change, burst water mains, flooding, defects in underground sustainable urban drainage (SUD) systems, defective soakaways and sewers, adjacent trees, sulfates, radon, methane, and other ground gases and contaminants.

Even when the site investigation indicates dry conditions, the risk of some waterlogging in the future should be assumed because even in a permeable subsoil, groundwater requires time to drain away, which can result in limited pressure periodically coming to bear against the structure.

The consequences of installing a damp proofing system where a waterproofing system should have been installed can be serious and very costly. Choosing the wrong system can cause a high probability of water ingress and flooding, with devastating consequential losses.