If you are considering using a liquid screed in Reading on a contract, you have probably read all about the many advantages that it has over and above the traditional type of sand and cement screed. However, you may also be asking yourself if liquid screeds have any disadvantages, and the answer is that, yes, they do. That is if you consider them disadvantages.
The first is that, if you are considering laying a screed in a wet room with a sloping floor, then you cannot use liquid screed for the rather obvious reason that it will all end up at the bottom of the slope!
The other disadvantage, if you can call it that, is that as a liquid screed dries it will produce a layer of very fine particles on the surface. This layer is called laitance, and you should not lay the final flooring directly on top of it because it will cause problems with adherence, especially if you are using tiling or stone which needs to be attached with an adhesive. You also need to use a special adhesive which can be used with gypsum.
Remove By Sanding
The layer of laitance needs to be removed by sanding, and this should be done between 7 and 10 days after the screed is poured. If it is left any longer, the laitance will harden and become more difficult to remove. Once the surface has been sanded it needs to be vacuumed in order to remove any remaining dust. Having the surface professionally sanded will add about £8.00 per square metre to the cost.
So, those are the two disadvantages of liquid screeds. All the rest are benefits, such as the speed of laying which is as much as 20 times as fast as laying a sand and cement screed by hand. Surprisingly, liquid screeds also dry very quickly. Depending upon weather conditions and temperature, you can walk on the screed in as little as 24 hours, and certainly no more than 48. That means that other contractors who need to work on the site are not unduly delayed.
You can also lay liquid screed a lot thinner than sand and cement, which means that if you are installing underfloor heating it will use less energy to reach operating temperature. There are also further benefits regarding heat transfer into the room and thermal conductivity.