Do you have walls that are damp, odours that smell musty, or has water entered your home that was just built? Then you are among several people who are also struggling with this problem. The key to stopping such a problem is in the correct understanding and use of moisture barriers in building works. These protective systems are your home’s first line of defense against water damage, mold growth, and structural deterioration. If you are thinking of a new building, or even refurbishing an old one, learning about moisture barriers can not only save your money in the future but also guarantee the longevity of your building.
What is a Moisture Barrier in Construction?
A moisture barrier is a product or a set of materials, which aims to stop water vapour and moisture from entering the building through the various components like walls, floors, and even the ground under a house. You can even consider it as a protective layer that prevents your home from getting wet and still allows the building materials in your house to experience air flow. By preventing moisture accumulation, these elements prevent issues like water seepage and leakage, which often lead to further issues like mould development, cracks and even structural failure.
Importance of Moisture Barriers in Concreting
Concrete construction, in particular, requires proper moisture control because concrete is treated with large quantities of water during the curing process. In case there are no proper moisture barriers, this leftover moisture can move up through concrete slabs, hence resulting in the malfunction of flooring materials that lie above. This issue becomes even more significant when we take into account that excess moisture can lead to the occurrence of adhesive failures in tile installations, hardwood floors and the production of mold beneath floor coverings.
Building codes often mandate installations of moisture barriers in concrete, particularly in below-grade areas where the earth is the source of moisture. Contractors who are professionals are aware of the consequences that skipping this step can lead to the necessity of expensive callbacks and warranty claims.
The Role of Moisture Barriers in Energy Efficiency
- Preserves Insulation Performance: Water barriers stop moisture in insulating materials from soaking through to the ground, thus allowing them to keep their complete thermal resistance. Non-wetted insulation leads to less wear of heating and cooling appliances.
- Minimises Thermal Bridging: If moisture penetrates walls or floors, areas of low temperature may appear that will cause more heat to escape. Barriers assist in stopping this moisture, hence a stable temperature between the different indoor zones can be maintained.
- Reduces HVAC Load: Moisture barriers help create air-tight surfaces, thus reducing the amount of heat exchanged between different spaces. This means that any mechanical ventilation equipment used will function more efficiently, leading to lower utility bills.
Types of Moisture Barriers
There are numerous ways in which the construction industry can address moisture barrier issues. Each barrier has its specifications, materials, and environmental conditions that it works best with. The first step in selecting the right one is to understand the different kinds of moisture barriers available.
Polyethylene Sheeting
Polyethylene sheets are considered the simplest and cheapest solutions for ensuring moisture prevention. These plastic films are usually between 4 and 20mm in thickness, with 6mm being the most standard one for residential use. Besides being highly water-resistant, the product is also very user-friendly, and thus it can be easily installed on large surface areas.
Cross-Laminated Films
Cross-laminated films are multi-layered composites of various materials that aim at providing moisture protection of the highest quality along with durability. Generally, these barriers have a polyethylene core that is placed between two different reinforcing layers, giving the product better guard against getting a small cut or from being torn, thus making them stronger than plastic sheets which are entirely made of one material.
Vapour Retarder Paint
Vapour retarder coatings are seen as a more convenient alternative to the traditional ones since the solution goes directly on the surface and creates a membrane that does not allow moisture to enter when cured. The essential component of these coatings is that they have small molecules that get attached to each other chemically on drying and thus they are tightly packed, therefore forming polymers that prevent moisture.
Asphalt Laminated Paper
Asphalt laminated paper or building paper is one that combines organic felt or paper backing with asphalt coating for moisture protection. The use of this traditional moisture barrier has been extremely widespread in the construction industry for many years, but is now mostly used in areas where materials such as glass and steel are mixed with other materials in construction.
Smart Vapour Barriers
Smart vapour barriers are state-of-the-art products in the field of moisture control and generally allow moisture to enter from one direction, but not the other. Their permeability is adjustable according to the humidity on both sides of the barrier. In the case of dry conditions, they allow the vapour to pass through, thus stopping the moisture from being trapped.
Fluid-Applied Membranes
Fluid-applied membranes are essentially moisture barriers that are continuous, flexible, and non-conductive with liquids. The main material is polymer-based, and the product can be applied as a spray, by a roller, or by brush.
Foam Insulation Boards
Rigid foam insulation boards not only keep the heat out but also act as a barrier against moisture. Products such as extruded polystyrene (XPS) and polyisocyanurate (PIR) foam have tightly packed cells that prevent the passage of water vapour and also provide excellent R-values for energy efficiency.
Sheet Metal
Typically, sheet metal moisture barriers made of aluminum or galvanised steel offer good resistance to moisture and are very long-lasting. Such barriers are generally found in heavy-duty machines and places that are in need of high mechanical strength.
Glass
Although glass barriers are rare in everyday construction, they can provide a complete seal from moisture and offer total resistance to chemicals. The use of special glass membranes or glass-based products is typically in laboratories and the pharmaceutical industry where there is a need for very strict moisture control.
Rubber Membrane
Rubber membranes offer perfect flexibility and long-lasting life for moisture barrier installations. These membranes retain their sealing features even under a very wide temperature range, and they are able to bear large structural changes without losing their continuity in functioning.
Self-Adhesive Bituminous Membrane
Self-adhesive bituminous membranes provide the waterproofing features of modified bitumen along with a hassle-free peel-and-stick installation. In these membranes, a polymer-modified bitumen compound is attached to a reinforcing mat from the bottom by a pressure-sensitive adhesive which enables easy removability and stickability.
EPDM Membrane
Ethylene Propylene Diene Monomer membranes are synthetic rubber fabricated layers that are less prone to weathering and are characteristically long-lived. These membranes are designed in such a way that they retain the greatest part of their flexibility at low temperatures and do not get affected by UV rays, therefore, they are very good for outdoor applications and in water bodies.
Polyurethane Membrane
Polyurethane membranes have excellent elongation properties and are able to firmly bond with most substrates. After curing, these elastomeric coatings become seamless, flexible barriers that can seal even tiny cracks and allow for structural movement at the same time.
Polymer-Modified Bitumen Membrane
Polymer-modified bitumen membranes improve the basic bitumen with the help of synthetic polymers to make the final product more flexible, resistant to temperature changes, and durable. The principal ways of modification are through the impregnation of bitumen with styrene-butadiene-styrene (SBS) or atactic polypropylene (APP) polymers that drastically raise performance characteristics.
Pre-formed Sheet Membranes
Pre-formed sheet membranes are barrier systems that are produced in a factory and delivered to the job site ready for installation. The main idea of these products is to layer different materials to obtain the desired performance against moisture, puncture, or imbibe other chemical properties.
Electrochemical Moisture Barriers
Electrochemical moisture barriers represent cutting-edge technology that uses electrical fields to repel water molecules from protected surfaces. These active systems require power to operate but can provide dynamic moisture control that adapts to changing conditions.
How and Where to Install Moisture Barriers
- Under Concrete Slabs: To prevent moisture from rising into the ground, install a polyethylene sheet or vapour barrier directly under the concrete slab. For a continuous barrier, overlap the seams by at least 6 inches and seal with construction tape.
- Basement Walls and Floors: Besides applying liquid membranes, or installing sheet barriers to walls, there are water seal systems for underground spaces where water pressure is high.
- Exterior Wall Assemblies: In order to keep houses dry and at the same time let fabrics breath, use smart vapour barriers or building wraps. The key to success in airtight sealing is accurate work at the meeting points of the wall with the roof, windows, and doors.
- Roof Assemblies: Drop the use of natural felt or other low-quality materials and go for asphalt laminated paper or synthetic underlayments to snuggle the roof deck and stop the infiltration of water. Weather resistant measures include complete coverage and sealing of overlaps.
- Under Flooring Systems: Moisture barriers like vapour-retarder films or coatings should be placed over concrete subfloors if hardwood or laminate floors are to be installed. This ensures that adhesives are protected from moisture and the wooden surfaces do not undergo warping.
- Foundation Walls: Apply self-adhesive bituminous membranes or rubberised coatings on the outside of foundation walls before backfilling. These barriers resist water pressure from surrounding soil and prevent infiltration into the basement.
- Crawl Spaces: Use polyethylene sheet that is continuous and free of holes over the ground of the crawl space and extend it till the foundation walls. Seal all the edges and seams so moisture from the soil will not enter the building envelope.
- Wet Rooms and Bathrooms: Install one layer of polyurethane or EPDM as a membrane for tiles in bathrooms, mainly around the shower and bathtub area. Otherwise, these spaces may be an easy target for moisture, which can especially be a problem if tiles are used.
How to Choose the Right Moisture Barrier
- Concrete Moisture Test Before the installation: Do a moisture test on the concrete slab or surface to find out the vapour emission rate. This enables you to select a barrier with the correct performance rating for efficient protection.
- Correspond to the Type of Flooring or Finish: Use the vapour barriers with high performance for the most moisture sensitive floorings such as hardwood or laminate. For floors with ceramic tiles or vinyl planks, vapour retarders of standard quality may be enough.
- Consider the Weather and Soil Conditions: In the case of humid areas with high ground water, choose materials that are made from cross-laminated film or self-adhesive membrane with thick and low permeability as the barrier. Such barriers are friendly in the long-term as they offer a lower chance of failure.
Conclusion
Error-free and durable construction projects require the understanding as well as use of correct moisture barrier systems. Investing in high-end moisture barriers is like planting a seed that will yield fruits in the form of lesser maintenance costs, great indoor air quality, and increased structural longevity. If you are building a new house or thinking of altering an old one, the right barrier selection and installation will be guaranteed if you engage the services of professionals who have relevant experience.The Brick & Bolt team of construction professionals is familiar with all the difficulties that arise in moisture control and can help you pick the right barrier system for your project with ease. Reach out to us now to schedule a meeting for your construction project and discover how the correct setting of a moisture barrier can be an excellent investment for you in the future.
Apoorva H P Achar