Fixing Your Self-Levelling Screed – From Pinholes to Laitance Removal
Screed problems? Pinholes, bubbles, or a dusty layer of laitance on your new liquid screed? It’s frustrating when your flooring project has flaws, leaving you wondering what’s gone wrong with your self-levelling screed and, more importantly, how to fix it. Understanding what causes these issues is the first step to a perfect finish. This guide will explain that, as well as the steps you can take to put it right.
At Capital Screeding, we’re not just suppliers and installers of flow screed across London, Essex, and the South East – we’re also experienced problem-solvers. With years of hands-on screeding, we’ve seen and fixed most things that can happen to screed. In this blog we’re putting that experience to use, offering you practical, clear advice you can trust.
Your Troubleshooting Guide to Flow Screed Surface Issues
Time to deal with screed surface problems. If you’re seeing little holes, bubbles, or a powdery finish on your flow screed, we can help. Screed flooring may throw the odd curved ball your way, but there’s usually a logical cause and a solid fix.
1. Pinholes in Your Self-Levelling Screed
Pinholes are tiny holes that look like craters on the floor surface. They often appear when:
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Air gets trapped – This can be from the subfloor, especially if it’s porous concrete that wasn’t primed correctly, or if the self-levelling screed was mixed a bit too vigorously.
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Substrate issues – A subfloor that’s too absorbent can suck moisture from the screed too quickly.
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Screed poured too thinly – This can prevent the material from de-aerating properly.
How to Fix Pinholes
If you’re seeing a few scattered pinholes, once the screed is fully dry, a light sand and a skim with a compatible levelling compound will usually fix it. For more extensive pinholing, make sure the surface is clean and dry, then apply a good quality acrylic primer or sealer, which will fill and seal them before your final floor finish.
2. Why You Get Blisters and How to Fix Them
Blisters tell you that there’s trapped air or moisture trying to escape. They appear as a result of:
Moisture from below -A damp subfloor or a faulty damp proof membrane (DPM) is usually the cause.
Faulty primer application – If the primer doesn’t create an effective barrier, air or moisture from the substrate can be released into the self-levelling screed.
Environmental issues – Rapid surface drying from direct sunlight or excessive airflow before the screed has fully set.
How to Fix Screed Blisters
For small, isolated blisters in flow screed, specialist epoxy injection can work. If they’re more widespread though, the affected sections will need to be carefully cut out. Then, make sure that the substrate is completely dry and correctly primed before infilling the area with fresh screed.
3. Understanding and Tackling Laitance
Laitance is a weak, dusty film you sometimes find on cured self-levelling screed. It’s made of fine particles and cement that rise to the top, often due to:
Too much water in the screed mix.
The natural settlement process of the screed components during curing.
Effective Laitance Removal for a Perfect Finish:
Laitance has to be removed before you move on to your final floor finish. If you leave it, your floor coverings won’t stick properly. Here’s what you need to do for laitance removal:
Patience is Key – Wait until the self-levelling screed is sufficiently cured.This is typically 5-14 days, when it’s hard enough for light foot traffic and you can work on it without damaging it. Don’t leave it longer, as the laitance will become harder to remove.
Sanding it Off – The standard method is to use a rotary sanding machine with an appropriate abrasive disc (around 60-80 grit is best). For edges or small areas, a hand-held sander or sanding block can be used. The aim is a gentle but thorough removal of the weak top layer.
Vacuum Thoroughly – Once sanded, a vacuum thoroughly to remove all fine dust, ensuring a clean surface for priming or adhesive.
Sealing – Once the laitance is removed the floor should be sealed so the floor covering adhesive or glue will stick / bond well to the substrate / screed.
Capital Screeding is Here to Help
Having the know-how to recognise and solve screed problems is what this blog is all about. Once you know what you’re dealing with, and how to fix it, you can achieve fantastic results. But, for those larger projects, trickier subfloors, or when you simply want the peace of mind that comes from experienced installation of self-levelling screed, Capital Screeding is here to offer that professional touch, with the guarantee of flawless floors.
Want your self-levelling screed installed perfectly? Get in touch with the Capital Screeding experts today on 020 3369 3396
