If you have ever put a marble down on the floor of a Victorian terrace and watched it roll off towards the bay window, you already know the problem: an uneven floor. Floors in older Liverpool homes are rarely flat, and almost never level. That matters far more than most people expect when new flooring goes down, because the finished floor can only ever be as good as the subfloor preparation underneath it. This guide explains why floors end up uneven, how to check yours, the main ways of putting timber and concrete floors right, what floor preparation typically costs, and why a flooring quote can change once the old floor comes up.
Flat and Level Are Not the Same Thing
Level means horizontal: a spirit level laid on the floor reads true. Flat means free of humps, dips and steps over a short distance, whether or not the whole floor slopes. For almost every type of flooring, flatness is what counts.
A floor that falls gently by 15mm from one side of a room to the other can usually take laminate, engineered wood or carpet without trouble, because the boards follow a gradual slope. A floor with a 5mm dip in the middle of the room will cause problems whatever goes on top of it: click joints flex and open, glued vinyl shows every ripple, and tiles rock or crack.
Level still matters in some situations. A pronounced slope makes doors swing open or shut on their own, leaves gaps under kitchen units and looks obvious where a floor runs into a room with a flat modern slab. But when a fitter talks about levelling a floor, what they usually mean is making it flat enough for the flooring you have chosen.
Why Floors in Older Liverpool Homes Are Uneven
Suspended timber floors in Victorian and Edwardian terraces
Most pre-war terraces across Liverpool have suspended timber ground floors: joists resting on low brick sleeper walls, floorboards nailed across the top and a ventilated void underneath. After a century or more, several things are usually going on at once. Sleeper walls settle unevenly. Joist ends sitting in damp brickwork soften. Boards cup and wear. And generations of plumbers and electricians have notched and drilled joists to run pipes and cables, sometimes deeply enough to weaken them, so the floor sags between supports.
1930s semis and upstairs floors
Inter-war semis in areas like Crosby, Maghull and Aintree often have better-built floors, but upstairs floors deflect over time, especially where heavy items such as baths or wardrobes have stood for decades, or where joists span a long way. It is common to find an upstairs room that dips towards the middle.
Concrete floors, extensions and kitchens
Solid concrete floors bring different problems: humps and hollows left by the original screed, cracked or crumbling screed, old quarry tiles and black adhesive left behind from previous floors. Where an extension meets the original house there is often a step or ridge between the two, because the floors were built decades apart to different levels.
Layers of old floor coverings
Old vinyl, hardboard, tiles and adhesive build up over the years. Each layer adds its own unevenness, and none of it should stay under a new floor. Removing it is often the first job, and only once it is up can the true state of the subfloor be seen.
A note on older floor tiles: small square thermoplastic or vinyl floor tiles, and some black bitumen adhesives, in homes built or refurbished before 2000 can contain asbestos. They should not be sanded, ground or broken up until they have been tested. If they are sound, they can sometimes be left in place and overlaid instead. The Health and Safety Executive publishes guidance on asbestos, and a reputable fitter will raise it before starting work rather than after.
How Flat Does a Floor Need to Be?
Every flooring manufacturer publishes its own tolerance, and it is worth checking the product you have chosen, because fitting outside it can void the warranty. As a general guide:
- Carpet is the most forgiving. Underlay absorbs small imperfections, but humps and ridges still show as wear lines over time.
- Laminate and click engineered wood typically need no more than around 3mm of variation under a 2m straightedge, and some brands ask for 2mm. Dips make the boards flex, which is what makes click floors creak and joints open.
- Glue-down LVT and sheet vinyl are the least forgiving. They are thin and follow every contour, so the subfloor needs to be flat and smooth. A smoothing compound is standard practice underneath them.
- Tiles need a flat, rigid base. Large format tiles need an especially flat floor, because a long, stiff tile cannot follow a dip.
Flooring professionals often describe concrete floor flatness using the surface regularity classes in British Standard BS 8204. SR1, the strictest, allows a maximum gap of 3mm under a 2m straightedge; SR2 allows 5mm; SR3 allows 10mm. Most domestic hard floor coverings need something close to SR1.
How to Check an Uneven Floor Yourself
- Straightedge test. Lay a long, straight length of timber or a 2m level on the floor in several directions. Look for gaps underneath and measure the biggest with a ruler or a stack of coins. Anything over about 3mm is likely to need attention before hard flooring goes down.
- Spirit level. Check the overall fall across the room. A gradual slope is usually fine; a sudden change is not.
- Walk it. Bounce gently on your heels across the room. Soft spots, bounce or creaking on a timber floor point to loose boards or problems with the joists underneath.
- Look at the edges. Gaps under skirting boards, doors that catch or swing on their own, and cracks where the floor meets the wall all suggest movement or settlement.
This gives you a good idea of what you are dealing with, but not the whole picture. The condition of a subfloor under existing flooring is impossible to judge fully until the flooring has been lifted.
How Timber Floors Are Put Right
Re-fixing and replacing boards
Loose boards are screwed down rather than re-nailed, so they stop moving and creaking. Split, rotten or badly worn boards are replaced. Pipes and cables have to be located before any screw goes in, which is one reason this part of the job takes longer than people expect.
Fixing the joists
If a floor sags, the fix is under the boards, not on top of them. Joists can be packed up where they sit on the sleeper walls, strengthened by bolting a new length of timber alongside (known as sistering), or replaced where the ends have rotted. Joists notched too deeply for old pipes or cables can be reinforced. Where there is damp or rot in the void, the cause, often blocked airbricks or bridged damp-proofing, needs finding and fixing too, or the problem will come back.
Overboarding with plywood
Once the structure is sound, the usual way to create a flat, stable surface over floorboards is to overboard with plywood, screwed down at close centres. Thin plywood, typically 6mm, is common under vinyl and LVT. Tiles need a thicker, stiffer build-up, usually 12mm or more of plywood or a tile backer board. Hardboard is still sometimes used under vinyl but is less stable in damp or heated rooms. Overboarding also covers the gaps between old boards, which cuts draughts as well as improving the finish.
Levelling compound on timber
Standard self-levelling compound is designed for concrete and will crack over timber, which flexes. Where a timber floor needs compound, the boards are overlaid with plywood first, primed, and finished with a flexible, fibre-reinforced compound made for timber substrates.
How Concrete Floors Are Put Right
Grinding and patching
High spots and ridges are ground down, loose or hollow-sounding screed is broken out and patched, and cracks are filled. Old adhesive residues are removed or sealed, depending on what they are and what the new floor needs.
Self-levelling compound
Self-levelling compound is a cement-based mix that is poured and spread, flowing out to a smooth, flat surface. Thin applications of a few millimetres are routine and are the normal preparation under LVT and vinyl. Deeper dips need a compound rated for greater thicknesses, sometimes laid in more than one pour. Most products can be walked on within a few hours, but the drying time before flooring goes down depends on the product, the thickness and the conditions in the room.
Screeding
Where a floor is well out, for example where an old concrete floor needs raising to meet an extension, a new screed may be the answer rather than compound. A traditional sand and cement screed takes considerably longer to dry than compound, and laying flooring on a screed that has not dried properly is one of the most common causes of flooring failure.
Checking for damp
Concrete floors in older houses often have no damp-proof membrane at all. Before a moisture-sensitive floor such as wood, laminate or LVT goes down, the floor should be tested with a hygrometer. Many manufacturers specify a maximum of 75% relative humidity, and some wood floors ask for less. If the floor is too damp, a liquid damp-proof membrane can be applied before the compound.
The Knock-On Effects of Raising a Floor
Every layer of plywood or compound adds height. A few millimetres rarely matters, but 15 to 20mm can have consequences people do not always think about:
- Doors may need trimming to clear the new floor.
- Thresholds between rooms need a neat transition, especially if one room is being done and the next is not.
- Kitchen appliances such as dishwashers and integrated fridges can end up trapped under the worktop if the floor is raised around them rather than under them.
- Skirting boards will sit lower on the new floor than before and are often best removed and refitted.
- Stairs are affected where a raised hallway floor meets the bottom step, because it changes the height of the first riser. This should be planned for rather than discovered.
Floor Levelling Cost: What Floor Preparation Typically Costs
Floor preparation is usually priced separately from the flooring itself, and it varies more than any other part of a flooring job because it depends on what is found. The figures below are broad, indicative UK ranges for 2026 to help you plan. They are not a quote; the cost for your floor depends on its condition, size and access.
| Job | Typical range |
|---|---|
| Lifting and disposing of old floor coverings | £5 to £15 per m² |
| Thin self-levelling compound on concrete (up to around 5mm) | £10 to £25 per m² |
| Deeper levelling or fibre-reinforced compound | £25 to £45 per m² |
| Plywood overboarding on a timber floor | £15 to £30 per m² |
| Replacing damaged floorboards | £45 to £120 per m² |
| Joist repairs or sistering | £150 to £400 per joist, more where access is difficult |
| Liquid damp-proof membrane | £5 to £15 per m² |
For a typical 15m² living room on a sound concrete floor, preparation might add a few hundred pounds. For the same room on an old timber floor that needs board repairs, joist work and overboarding, it can run to over a thousand. That difference explains most of the gap between a cheap flooring quote and a realistic one.
Why Your Flooring Quote Might Change Once Work Starts
An honest flooring quote for an older home will usually do one of two things: include a clear allowance for preparation, or state that preparation will be confirmed once the old floor is lifted. Neither is a warning sign. What should concern you is a quote that says nothing about preparation at all, because it usually means the new floor will either be laid over whatever is there, or the cost will appear later. The same thing happens on bathroom jobs, as we explain in our guide to what is behind your old tiles.
Questions worth asking any fitter before you book:
- How will you check the subfloor, and when?
- What flatness does this flooring need, and how will you achieve it?
- Is preparation included, or priced once the old floor is up?
- How long will the compound or screed need before the flooring goes down?
- Will doors, skirting boards or appliances need adjusting?
How Long Floor Preparation Takes
On a straightforward room, preparation adds a day or less: lifting the old floor, small repairs, overboarding or compound, and drying time before the new floor is fitted. Joist repairs, damp treatment or a new screed can add several days, and a full screed can need weeks to dry before moisture-sensitive flooring goes down. Planning for this from the start avoids the frustration of a job that seems to stall halfway through.
If the floor you are planning is in a bathroom, our guides to vinyl, LVT or tiles for a bathroom floor and tile backer board versus plasterboard go into more detail, and if you are considering heating under the new floor, see our bathroom underfloor heating cost guide. Owners of older terraces may also find our guide for Victorian terrace owners useful.
About Kew Construction
Ariel runs Kew Construction from Liverpool, a family-run business delivering building, renovation and flooring work across Merseyside. Kew Construction holds two verified Google Business Profiles covering Liverpool and the surrounding area, and is reviewed on Checkatrade, MyBuilder and Trustpilot. If your floors are uneven and you are planning new flooring, call Ariel on 07453273876 or email Info@kewconstruction.com. Finished work is on Instagram.
Frequently Asked Questions
Can you lay new flooring on an uneven floor?
Carpet can go over small imperfections, but hard floors such as laminate, engineered wood, LVT and tiles need a flat subfloor. Laying them on an uneven floor leads to creaking, opening joints, visible ripples or cracked tiles, and can void the manufacturer’s warranty. The subfloor should be brought within the product’s tolerance first.
How much does it cost to level a floor in the UK?
As a broad guide, thin self-levelling compound on a concrete floor costs around £10 to £25 per m², and plywood overboarding on a timber floor around £15 to £30 per m². Structural repairs such as joist work are priced separately. The total depends on the condition of the floor, which is only fully known once the old flooring is lifted.
Can self-levelling compound be used on floorboards?
Not directly. Standard compound is designed for concrete and cracks over timber because timber flexes. Floorboards should be overboarded with plywood, primed and then covered with a flexible, fibre-reinforced compound made for timber floors.
How uneven can a floor be for laminate or LVT?
Most laminate and click flooring manufacturers allow around 3mm of variation under a 2m straightedge, and some ask for 2mm. Glue-down LVT needs a floor that is both flat and smooth, which is why a smoothing compound is normally laid first. Always check the tolerance for the specific product.
How long does self-levelling compound take to dry?
Most compounds can be walked on within a few hours. The time before flooring can be laid depends on the product, how thick it is and the conditions in the room, ranging from the next day for a thin layer to considerably longer for deep applications. Traditional sand and cement screeds take much longer than compound.
Do I need to level a floor before fitting carpet?
Usually not to the same standard as hard flooring, because underlay absorbs small imperfections. Loose or creaking boards should still be fixed, and pronounced humps or ridges levelled, as they show through as wear lines over time.
Why do floors in Victorian houses slope?
Victorian houses usually have suspended timber ground floors on brick sleeper walls. Over more than a century, sleeper walls settle, joist ends soften in damp brickwork, and joists are weakened by notches cut for pipes and cables, so floors sag and slope. Many slopes are gradual and harmless, but dips and bounce need fixing before new flooring goes down.
Which areas does Kew Construction cover?
Kew Construction is based in Liverpool and works across Merseyside, including Crosby, Formby, Maghull, Aintree, Bootle and the Wirral.