In arid places where there are no soils or drainage issues, slabs-on-ground do not require substantial protection against water penetration and moisture.If there are no irrigation activities in the region, this precaution is not necessary. This is the case unless the region’s building code necessitates treatment. However, for all site circumstances other than those listed above, water proofing or damp proofing for slabs built on grounds is required.According to ACI 302. IR-89, there is no need for damp proofing, water proofing, or vapour retarders on well-drained sites or sites that meet the following criteria:The water table level at the site is very low when compared to the land surface a foundation.
Damp Proofing of Slabs–on–Ground
Damp proofing slabs built on the ground can be done from both below and above the surface. The damp proofing is usually put below the slab’s surface. As a damp proofing membrane, most vapour retarder plastic films are used below the slab surface. The installation of a vapour retarder over the surface of a gravel substrate is shown in. As indicated, the vapour retarders are attached to the foundation wall. This will ensure that the location is consistent.Brick chairs, rather than wire chairs, are used to prevent sheet penetration.
When wood flooring must be installed above slabs on the ground, damp proofing is applied to the floor’s surface. Only under the following circumstances is damp proofing over the slab top surface permissible: The slab surface is at least 12 inches below the water table.The installation of footing drains takes place. Unless the foregoing parameters are met, the slabs-on-ground with timber flooring on top will require moisture proofing. The installation of wooden flooring over the slabs built on the ground is shown in. shows how the wood flooring span sleepers will separate the surface from the bottom slab. Only the slab beneath the subfloor can be damp proofed.
Wooden Flooring Above Slabs-on-Ground
An air space is formed between the timber flooring and the slabs produced in. Water penetration owing to water vapour migration must be avoided, hence this must be vented at the joints. This will aid in maintaining an even relative humidity above and below the surface of the offered wooden flooring. The partitions and columns present will interrupt the top surface damp proofing of the slabs constructed on the ground. These extra parts will disrupt the vapour retarders, resulting in the damp proofing system’s integrity being compromised. The same can be seen in. In these instances, damp proofing or water proofing beneath the slab is the best option.
Risk in Using Vapor Retarders as a Waterproofing Solution
Risks will be welcomed if vapour retarders are used instead of water proofing. The vapour retarder’s performance is determined by the film’s integrity as well as how it is seamed. In a slab on ground construction, maintaining vapour retarder seam integrity in the field is quite challenging.Vapor retarders are also put at danger by the usage of wooden or vinyl coverings. The usage of wall-sensitive adhesives is another potential factor. In these cases, it is preferable to install a heavy-duty panel or water proofing rather than risk the loss that comes with a total replacement of a moisture-damaged floor. The attachment of sleepers to slabs-on-ground must be done as shown in figure 2.
Considerations in Damp Proofing Slabs on Ground
When damp proofing the top surface of the slab, the slab should have a granular substratum. This layer of suitably graded aggregate will aid in the prevention of moisture accumulation (mainly by the principle of capillary action). Suspenders and other belts should not be used as a vapour retarder beneath the slab surface, and damp proofing should be applied to the top surface. The vapour pressure created by the residual moisture in the concrete slabs might disperse the vapour retarder, causing it to break. It is not advisable to have an excessive number of floor treatments and coatings. This is due to the concrete’s sensitivity to moisture. Moisture-sensitive adhesives are a type of moisture-sensitive glue that can be utilised in a variety of applications.
Moisture in concrete has been caused by liquid applied coatings on concrete slabs on the ground. High levels of moisture content can be caused by the following circumstances: For slabs that are cast on a grade where the under-slab vapour retarders do not function properly. When suspended slabs are cast over non-vented steel formworks, the following conditions occur.Conditions in which the suspended slabs are built over occupancies with a greater relative humidity. Commercial kitchens and swimming pools are examples of this.The placement of suspended slabs over unventilated crawl areas.Lightweight aggregates are used in the slabs.Water cement rations greater than 0.55 (w/c = 0.55) were employed in the slabs.The slabs that took less than 90 days to cure.
Manufacturers of floor finishes or damp proofing coatings strictly adhere to the need of thoroughly evaluating the concrete slab prior to applying any membranes. This testing will ensure that the moisture content in the slab is within the susceptible limits and won’t result in any failure. The Calcium Chloride Test as specified by ASTM F1869 is used to determine the Moisture Emission Rate (MVER). This is measured in pounds per thousand square feet within 24 hours. The accepted range of MVER is three to five pounds.The internal relative humidity in the structure is obtained by means of a hygrometer by placing probes in concrete. This is as per ASTM F710 and the established rate is 75 percent.This result can be achieved within.
Liquid epoxy DPM for existing concrete floors
Where a current DPM has failed or was never placed, a Liquid Epoxy Damp Proof Membrane (DPM) is frequently employed as a corrective remedy. The epoxy DPM is sold as a two-part system. It has a minimal odour, is solvent-free, and most significantly, it works with low moisture levels in concrete floors. Using a liquid epoxy DPM has a lot of advantages: An epoxy liquid membrane is placed to the concrete slab itself, creating an impermeable covering that keeps water out. This is in contrast to plastic DPM, which sit above the concrete slab and may allow water to pass through to the concrete’s surface. When the surface water travels to the boundaries of the pond, this becomes an issue.
Epoxy floor coatings can be utilised on existing concrete floors in factories, commercial buildings, and offices for their visual impact with their high shine surface and variety of colours, as well as acting as a DPM for those looking for a decorative finish. Epoxy membranes can be put directly on damp floors, eliminating the need to remove the existing concrete screed, which is a costly, time-consuming, and unpleasant process. You also save time by not having to wait for the floor to dry before applying the damp resistant layer.
Before putting an epoxy membrane, you must first prepare the concrete surface. You can use a nylon roller and brush to paint on the liquid membrane once the surface is clean and free of any previous coatings, debris, and surface water. Allow at least 12 hours but no more than 48 hours between coatings when applying multiple coats. A minimum of two coats is suggested, with up to three coats depending on the moisture level of the slab.If the product is installed on a concrete surface without a damp proof membrane or where the damp proof membrane has become ineffective owing to damage, you should take into account the possibility of hydrostatic pressure.
Fully isolate the dampness in the floor using a surface Damp Proof Membrane (DPM).
Remove Standing Water. The first step is to remove standing water from the area.
A DPM (damp proof membrane) is a plastic sheet membrane that sits between a concrete slab or screed.
Constructability in Construction and Issues at Design and Execution