External Floor Screed
I’m Andy Parkin, Managing Director of the Multi-Award-Winning Speed Screed. Generally, if we’re talking about any external floor screed, it tends to be concrete. Of course, screed and concrete terminology can be a little bit confusing at times. Which is which, can they both be the same?
What is external floor screed?
There are a few questions we need to ask
- Is the screed to be covered?
- Do you require a base for something else to go on top?
- Perhaps bedding for some slabs?
- To sit decking on?
- Does it need to be a wearing surface?
- Some other reason that you actually want that particular substrate?
Some of the external floor screed that we can provide can be non-structural but still wearing. If it is a wearing screed, that means you can traffic it. It doesn’t need anything on top to prevent damage through wear and tear. Do you need it as a wearing surface or is something going on top that is going to be that wearing surface?
One of the differences between internal and external floor screed is of course going to be site conditions. If we are working indoors, we are very much protected from the elements. If you are working outdoors, you are exposed to them, and the issues that you get.
If it is cold you are looking at the potential for freezing and damaging the screed. The screed contains water, so if that water freezes, you are going to have issues. Freezing water expands by approximately 9%, so you can imagine what that might do to a screed. You are probably going to end up with a dusty/cracking surface.
Hot weather, is the other side of the coin. The moisture in the screed is there partly to hydrate the cement. In hot weather that moisture can be lost, and then you will have un-hydrated cement particles within the screed. The result is a weak screed with a dusty surface.
I think we have all seen slabs that are dusty, concrete garage bases where they have been poured in hot weather, and lost the moisture out of the concrete.
Wind is a big factor. You may not think it is particularly hot on that day, but it can just pull the moisture out of the screed. If you imagine you are drying your clothes on a windy day, it dries them very, very quickly even if it is not that hot.
Site conditions need to be controlled.
Rapid Strength Screed
If we are going to be experiencing these types of challenges, then perhaps we need a rapid strength screed that is going to go off quickly and not be as affected by the site conditions.
This might be something that you would factor into the specification of the mix that you are looking for. The quicker it gains strength, the quicker it hydrates, and the less likely you are going to have any damage due to external factors.
Another consideration we need to make is do you have a structural substrate? If you don’t and you need one, then you are going to have to look at structural concrete.
This should have given you food for thought, and if you need further information please let us know.