Subfloor preparation
The single biggest reason a resin floor fails early is not the resin, it is what was underneath it. A coating laid over dust, laitance, an uneven slab or a floor that still holds moisture will lift, crack or peel no matter how good the system is. Subfloor preparation is the groundwork that prevents all of that, turning whatever is there now into a sound, clean, level base the finished floor can bond to and last on.
Surface Specialists arranges subfloor preparation as part of every resin flooring project, from mechanical grinding and shot blasting to screeding, levelling and damp-proofing. We assess the substrate and arrange the right preparation by experienced specialist contractors, so the base is ready before any coating goes down. You deal with one point of contact throughout. This page explains what subfloor preparation involves, the methods used and why it matters so much.
What is subfloor preparation?
Subfloor preparation is the work done to a concrete slab or existing floor to get it ready to take a new surface. It covers mechanically opening up and cleaning the surface so a coating can bond, repairing cracks and damage, levelling out an uneven floor and dealing with any moisture in the slab. The aim is a sound, clean, flat, dry base, because that is what every resin floor, screed and coating depends on.
It is sometimes called floor preparation, surface preparation or concrete preparation, and the exact work depends on the condition of what is there and the system going on top. A new slab needs different treatment from a tired old floor, and a heavy-duty industrial coating asks more of the base than a light domestic one. The preparation is specified to suit, rather than applied the same way to every floor.
Why does subfloor preparation matter?
A resin floor bonds to the surface it is laid on, so that surface has to be sound and clean for the bond to hold. Bare concrete carries a weak, dusty layer called laitance, along with dirt, old coatings, oil and curing residues, and a coating laid straight over that is really only stuck to the dust. Mechanical preparation removes it and opens up the surface so the resin grips the solid concrete underneath.
The same goes for the shape and condition of the floor. An uneven slab telegraphs every dip and high spot through a thin coating, cracks left unrepaired come back through the new surface and a slab holding moisture lifts a coating from below. Getting the base right is unglamorous but it is the difference between a floor that lasts twenty years and one that needs relaying in two, which is why we treat it as the foundation of the whole job rather than an afterthought.
Surface preparation: grinding and shot blasting
The first step is almost always to mechanically prepare the surface, removing the weak top layer and any old coating and giving the concrete a clean, slightly roughened profile for the resin to key into. The right method depends on the floor and the system going on.
Diamond grinding
Diamond grinding uses rotating diamond-tipped heads to grind back the surface, taking off laitance, old paint and adhesives and flattening minor high spots. It is the standard preparation for most resin coatings and leaves a clean, even surface ready to coat. It also lifts stubborn old floor finishes that would otherwise stop a new system bonding.
Shot blasting
Shot blasting fires fine steel shot at the floor to clean and texture it in one pass, leaving a consistent profile across a large area quickly. It suits bigger industrial and warehouse floors and is often the most efficient way to prepare a large slab for a heavy-duty system.
Both are dust-controlled processes, and which one is used comes down to the size of the floor, its condition and the coating it is being prepared for. This is confirmed at survey. See our sanding and grinding page for more on mechanical surface preparation.
Floor screeding and levelling
Where a floor is uneven, worn or simply not flat enough for the finish going on top, it is screeded or levelled before coating. A flat base is essential, because a thin resin coating follows the contour of the slab and shows every dip and ridge.
Floor screeding and liquid screed
A screed is a layer laid over the slab to bring it up to the right level and provide a smooth, sound surface to build on. Traditional sand and cement screeds and modern liquid or flow screeds both have their place, with liquid screed flowing out to a very flat finish over large areas. The right screed depends on the depth needed, the timescale and what is going on top.
Self-levelling compound
For smaller corrections, a self-levelling compound is poured over the prepared slab and flows out to iron out minor undulations and create a smooth, level surface. It is the usual answer where a floor is basically sound but not quite flat enough for a seamless resin finish.
See our floor screeding page for more on screeds and levelling.
Damp-proofing and epoxy DPM
Moisture is one of the most common reasons a floor coating fails. A slab that still holds construction moisture, or an older floor with no working damp-proof membrane beneath it, pushes moisture up into the coating and lifts it from below. The slab is tested for moisture as part of the survey so this is caught before any work starts.
Where readings are high or the slab is new, an epoxy damp-proof membrane is applied first. This is a resin barrier rolled or trowelled onto the prepared slab that holds the moisture back and lets the floor go down without waiting weeks or months for the concrete to dry naturally. It is what allows a project to proceed on schedule on a slab that would otherwise not be ready. See our epoxy DPM page for more on damp-proofing a slab.
Concrete repairs
Preparation also means making good the damage in a floor before anything is laid over it. Cracks, spalling, pitting, worn joints and patches of failed concrete all have to be repaired, because they come back through a new surface if they are left. We cover crack injection, patch repairs and joint repairs as part of getting a floor ready. See our concrete repairs page for detail.
How is a floor prepared for resin?
Every floor is different, but the process generally follows the same order:
- Survey and moisture test. The slab is assessed for soundness, level and moisture, and the condition sets the preparation needed.
- Mechanical preparation. The surface is ground or shot blasted to remove laitance, old coatings and contamination and to create a key for the resin.
- Repairs. Cracks, spalling and damaged areas are made good so they do not return through the new floor.
- Damp-proofing. Where moisture readings call for it, an epoxy damp-proof membrane is applied.
- Levelling. Screed or self-levelling compound is used where the floor needs bringing to level.
- Priming. The prepared surface is primed so the resin system bonds correctly.
Only once the base is sound, clean, level and dry does the finished floor go on, which is what gives it the best chance of lasting.
Why choose Surface Specialists?
Preparation is the part of a flooring job that is easiest to cut corners on and hardest to put right once a floor is down. That is why we treat it as the foundation of the work and arrange it properly, with one point of contact looking after the project from start to finish.
- A specialist focus. We concentrate on resin and surface treatment, so the preparation is matched to the substrate and the system going on rather than a one-size-fits-all answer.
- Experienced contractors. Preparation is carried out by established specialist contractors with the right equipment for grinding, blasting, screeding and damp-proofing.
- Right base, first time. The slab is assessed for soundness, level and moisture so the floor goes on a base that is genuinely ready.
- One point of contact. From survey through to a prepared, coated floor, you deal with us.
Subfloor preparation underpins our commercial and industrial resin flooring as well as domestic driveways and garage floors. Learn more about Surface Specialists or explore the full range of resin flooring we cover.
Areas we cover
We arrange subfloor preparation through experienced specialist contractors and are steadily extending the areas we cover. See our areas we cover hub for local detail, including resin flooring in Manchester, with more local pages being added.
Get a quote
Tell us about your floor and what is going on it and we will arrange a free site survey, then provide a written specification and quotation, typically within 48 hours. There is no obligation. Contact us to get started.
GET A FREE SITE SURVEY & QUOTATION
Frequently asked questions
What is subfloor preparation and why is it needed?
Subfloor preparation is the work done to get a slab ready for a new surface: mechanically cleaning and profiling it, repairing damage, levelling it and dealing with moisture. It is needed because a resin floor bonds to what it is laid on, and a coating over dust, an uneven slab or a damp floor will fail. The base is what makes the floor last.
What is the difference between diamond grinding and shot blasting?
Both mechanically prepare a concrete surface. Diamond grinding uses rotating diamond heads to grind back the surface and is the standard for most floors, including lifting old coatings. Shot blasting fires steel shot to clean and texture large areas quickly and suits bigger industrial slabs. Which is used depends on the floor and the system going on.
What is liquid screed and self-levelling compound?
Both bring a floor to level. A liquid or flow screed is poured over the slab and flows out to a very flat finish, used where a layer of build-up is needed. A self-levelling compound is a thinner pour for smaller corrections, smoothing out minor dips in a floor that is otherwise sound. The right one depends on how much correction the floor needs.
Do I need an epoxy damp-proof membrane?
Only where the slab holds enough moisture to risk lifting a coating, which is common in new slabs and older floors with no working damp-proof membrane. The slab is moisture-tested at survey, and where readings are high an epoxy damp-proof membrane is applied so the floor can go down without a long wait for the concrete to dry.
Can you prepare an existing concrete floor?
Yes. Most projects involve preparing an existing slab rather than a new one. It is ground or shot blasted, repaired, levelled and damp-proofed as needed, then primed ready for the new system. The condition of the floor is assessed at survey and the preparation specified to suit.
How much does subfloor preparation cost?
It depends on the size and condition of the floor and how much work it needs, from a straightforward grind and prime to extensive repairs, levelling and damp-proofing. We assess the slab at survey and set it out in a clear written quotation, so the preparation is costed as part of the whole job rather than as a surprise later.
Which areas do you cover?
We work through a network of experienced specialist contractors and are extending the areas we cover. Contact us to confirm cover for your project.