Semi Dry vs Flowing Screed Which is Best
I’m Andy Parkin, Managing Director of the Multi Award Winning Speed Screed.
I’m here to talk about Semi Dry vs Flowing Screed Which is Best?
Semi Dry Screed
Semi Dry Screed is Traditional Screed, a 1-4, a 1-3 type mix ratio. Semi Dry is used in 80% of all the screeding projects in the UK. It has certainly been around for years and is still the most popular screed.
There are certain benefits to using it.
- You are able to obtain a high degree of accuracy with it because you are finishing it with 2 or 3 meter straightedge. It allows you to be very accurate, it’s only accurate in the hands of trained installers. You would need the trained installers but if you’ve got that, they should be able to achieve a finish which will easily surpass what is actually required for the project.
- Able to use it in wet rooms, to form falls, and not have issues if the screed gets wet (an issue with calcium sulphate flowing screeds).
- Able to put additives in the mix, such as fibers in to reduce shrinkage. Anything with water in shrinks, and if you are wanting to avoid shrinkage cracking, the appropriate fibers go into the mix.
- A fast drying additives can be added to the screed, if you need to put the floor coverings on within a particular timescale and can’t wait for the traditional long drying times of, 2 months, even 3 months in certain circumstances.
- Additives can increase the strength, the early day strength and 28 day strengths. If the screed needs to be loaded in the in the early days, additives can be used to increase that strength to take the early loading.
Lots of benefits.
Screed can be mixed onsite or delivered ready mixed from the local plant. There are a number of advantages mixing the screed on site (using trained and accredited installers). When mixing on site, you can stop and start exactly where you need to. If taking pre-mixed screed you have got to wait for delivery vehicles to make the delivery on the day, and then if you have any delays once the material has been delivered the product will be going off. Pre-mixed screed has a limited time for it to be used, and once past this point it will need to be scrapped/removed from site. If the screed has gone off this will involve breaking the screed up.
You can control when and where you lay and when you stop so, it’s the most convenient for you. You often find that you end up with less waste using this product, as you can place day joints exactly where you want them rather than continuing to screed to use up a delivery of pre-mixed screed, and then finding the day joint causes issues for the following trades.
Flowing Screed benefits I think centre around productivity. A traditional screed team will typically lay about 125 square meters in a day. The number of teams can be multiplied to increase that productivity. With Flowing Screed potentially, depending on the size and shape of the building, you may be able to lay in the region of 1,000 to 1,500 square meters per day.
- Productivity is certainly an advantage of Flowing Screed over sand and cement.
Flowing Screed has a greater density than a Semi Dry Screed, and what that means to a Heated Screed is the thermal conductivity will be better. The Screed will heat and cool quicker and be more cost effective.
Both products all have different minimum depths for bonding, on insulation, and on membranes. Semi Dry Screeds can be modified to go thinner than a traditional screed, and there are some Flowing Screeds with extra strength which will allow the Screed to go down even thinner.
It really depends on your requirements and I think what we would always try to do is to one have a product and then sell that to a customer. The requirements of the customer should be identified and then, the appropriate product matched to the requirements.
It is a case of finding out exactly what you need and what you don’t need:
- When do you need to traffic it?
- Do you need it dry in a certain time?
- Need good thermal conductivity?
These type of questions are going to be very important. But please, speak to us for further information and we would be happy to help.