Concrete Slab Rooftops: Waterproofing Options You Can Go For
Having concrete slabs for rooftops is one of the roofing alternatives you can use on a storey building. However, you have to make the concrete rooftop waterproof so that it doesn't soak in case of rain. If the roof slab is not waterproof, water seeps into the cured concrete and interferes with its structural integrity. For instance, the water creates a conducive environment for rusting, corroding the structural steel. Eventually, the steel may not be able to hold the weight of the slab and may collapse in the end. Thankfully, there are many alternatives you can use to induce waterproofing qualities in the concrete rooftop. Here they are:
When laying the concrete, you can use cementitious waterproofing products to induce waterproofing qualities in the slab. When these products are added to the fresh concrete you want to lay, they react chemically to form long and narrow crystals that fill up any pores in the concrete as the concrete cures. The chemical reactions are stimulated by water, meaning that the crystals will continue to form if there are any pores letting water through the concrete. Cementitious products are efficient because the concrete cures together with the products, making the slab waterproof in all places and not just on the surface.
With sheet membranes, a thick film of waterproof material is used to stop water from coming into contact with the concrete slab. The films are made using rubberised asphalt, which forms a polyethylene film. Asphalt is very sticky and takes longer to apply compared to the cementitious alternative. The smooth glossy finish makes the water slip off the concrete roof when it rains and stops it from forming small pools and penetrating into the concrete. If any part of the sheet membrane is damaged, you can easily patch up the hole using asphalt.
There are different types of liquid membrane, such as asphalt and polyurethane. With a liquid membrane, a roller, trowel or spray is used for application. After the membrane cures, it forms a rubbery cover over the concrete surface. When dealing with joints and voids, your workers may requires additional materials such as cement. The liquid membrane is advantageous because of the ease of application and the low laying cost compared to the other waterproofing option. On the downside, there may be inconsistencies in coverage, especially when applying the membrane around joints and gaps where the membrane material has to be joined with the other material used to fill the gaps.