Plastering Floats: Which Type You Need and How to Use Them
The UK guide to plastering floats. Poly vs sponge, when to use each, the fingertip timing test, and what to buy from £5 upwards.
A wall of freshly skimmed plaster that's been trowelled too early, or too late, dries patchy and uneven. You sand it back, re-skim, and lose a full day. Or worse, you live with it and notice ripples every time the light catches the wall at an angle. The plastering float is the tool that controls the finish between application and final trowelling, and using the right one at the right moment is the difference between a flat wall and a frustrating re-do.
If you're paying a plasterer, understanding what a float does helps you judge their work. If you're skimming a small room yourself, it's one of the first tools you'll reach for after the trowel.
What it is and when you need one
A plastering float is a flat rectangular pad with a handle on the back. You press it against wet plaster and move it in broad strokes to smooth, flatten, and refine the surface after the plaster has been applied with a trowel. It's not for applying plaster (that's the trowel's job) and it's not for holding plaster (that's the hawk). The float sits between application and finishing.
The trade uses "float" and "trowel" almost interchangeably, which causes real confusion for homeowners. Walk into Screwfix and you'll find products labelled "plastering trowel" that are actually floats, and "poly floats" next to "finishing trowels" with no clear explanation of the difference. The simple distinction: a finishing trowel is steel, flexible, and used for the final polished pass. A float is plastic, sponge, or rubber, stiffer than a trowel, and used for the intermediate smoothing and texturing stages.
You need a float whenever plaster goes on a wall or ceiling. Skim coat on plasterboard, sand and cement render on blockwork, patching repairs. Even if you never plaster a wall yourself, knowing what a float does helps you understand why your plasterer's timing matters so much.
Types of float and when each one matters
There are more float variants than most people expect. For a homeowner doing a single room, you only need two. But understanding the full range helps you avoid buying something that looks right but does the wrong job.
Poly (plastic) float
The workhorse. A one-piece polyurethane moulding with a patterned, non-absorbent face. You use it to flatten and smooth plaster after application, pressing out air pockets and levelling ridges left by the trowel. The patterned face creates just enough friction to grip the plaster surface without dragging or tearing it.
Poly floats are cheap and hard to get wrong. A standard 280mm x 140mm poly float from Wickes or Toolstation costs under £5 and will last an entire project. OX Pro and Refina versions cost a few pounds more and feel slightly better in the hand, but a budget poly float does exactly the same job.
Sponge float
This is the one that transforms results for beginners. A sponge float has a 20mm layer of natural rubber sponge bonded to a plastic backing plate. You dampen the sponge, press it to the plaster surface, and work in circular or figure-of-eight motions. The damp sponge does two things simultaneously: it lightly moistens the surface (which reopens the plaster's working window) and it smooths out imperfections that the trowel or poly float left behind.
Sponge floats come in three grades, and the grade matters:
| Grade | Best for | Face texture |
|---|---|---|
| Fine | Gypsum skim coat on plasterboard, lime plaster | Smooth, tight-cell sponge. Produces the smoothest finish. |
| Medium | Lightweight backing coat, standard render | Open-cell sponge. More aggressive texture for thicker coats. |
| Coarse | Monocouche render, heavy sand-and-cement render | Very open-cell. Pulls the surface into a consistent coarse texture. |
For a single-room skim on plasterboard (the most common DIY plastering job), a fine sponge float is what you want. If you're rendering external blockwork on an extension, you'll need a coarse grade.
Other float types you'll see
Devil float (also called a scratch float): a poly float with nails or screws poking through the face. Used to score (or "key") the first coat of plaster so the second coat bonds properly. Some plasterers make their own by driving four or five screws through a cheap poly float. You can do the same thing with an old kitchen fork in a pinch.
Angle float: a small stainless steel float with a 90-degree lip, designed for pressing plaster into internal corners. Useful if you're doing a whole room. Not essential for a single patch repair.
Wooden float: the traditional version, now largely replaced by poly. Gives a slightly sandy texture. Still used in heritage work with lime plaster but unnecessary for modern gypsum plaster.
How to use a float properly
This is where most guides stop at "smooth the plaster" and leave you guessing. Floating is a timed process. Do it too early and you'll tear the plaster off the wall. Do it too late and the surface has set beyond the point where a float can do anything useful.
The fingertip test
This is your timing guide. Press your fingertip into the plaster surface. You're looking for a specific feel:
- Too early: your finger sinks in and plaster sticks to it. Wait longer.
- Ready: your finger leaves a slight dent but the plaster doesn't stick to your skin. This is your window.
- Too late: the surface barely marks. You've missed it. You can try misting with water to reopen the window, but results are unpredictable.
For gypsum skim plaster on plasterboard, the window arrives roughly 10 to 20 minutes after application, depending on room temperature, humidity, and how thickly you've applied it. Sand and cement render takes longer: wait until a firm thumb-print is possible without the surface deforming. Lime plaster sits somewhere between the two.
Sponging too early is the number one beginner mistake. Community forums are full of first-timers who went in with the sponge float after five minutes and pulled the plaster off the wall. Wait for the fingertip test. Every time.
Poly float technique
Once the plaster passes the fingertip test, take the poly float and hold it almost flat against the surface, angled at roughly 15 to 20 degrees. Work in broad, sweeping passes across the wall. Apply firm, even pressure. You're not trying to push plaster around at this stage. You're compressing and flattening what's already there.
Move from the bottom of the wall upward, then come back down from the top. This catches ridges from both directions. Pay attention to the edges where your trowel passes overlapped during application. Those overlap lines are where ridges form, and the float is what removes them.
Sponge float technique
After the poly float pass (or instead of it, depending on your approach), dampen your sponge float under a tap or in a bucket. Wring it out so it's just damp, not dripping. A soaking wet sponge will dump too much water onto the plaster and wash the surface.
Press the sponge to the wall and work in circular or figure-of-eight motions. Firm pressure, but not so hard that you're squeezing water out of the sponge. The sponge redistributes moisture across the surface, bringing the plaster back to a workable state. It also levels minor bumps and fills small hollows.
After sponging, you have roughly five minutes before the plaster pulls in and firms up again. That's your window for the final trowel pass. The surface goes from a wet glossy shine to a slightly satin, duller look. When you see that change, pick up your finishing trowel and make your final pass. Don't wait longer.
Clean the sponge face frequently. Plaster builds up on the sponge and starts scratching the surface. A quick rinse in a bucket of clean water between passes takes five seconds and prevents visible score marks in the finished wall.
Corners
Cut back internal corners with an angle float or the edge of your trowel after floating the main surface. Don't try to push a full-size float into a corner. It will gouge the adjacent wall.
How to check your plastered finish
Once the plaster is dry (allow 48 hours minimum, longer in cold or damp conditions), you can check whether the float work produced a flat, true surface. NHBC Standards require plastered surfaces to be flat within plus or minus 3mm when checked with a 2-metre straight edge. That's the professional benchmark.
Hold a 2-metre straight edge (or the longest spirit level you have) flat against the wall and look for gaps between the edge and the plaster. Slide it across different areas of the wall. Any gap greater than 3mm over that span is a defect worth raising with your plasterer.
Walls should be within 8mm of plumb over their full height (up to 3 metres). Check with a 1200mm or 1800mm spirit level held vertically against the wall.
Shine a work light across the wall at a low angle. This raking light reveals ridges, hollows, and trowel marks that are invisible under normal lighting. Professional plasterers do this as a final check. So should you.
What to buy
For a homeowner doing a single-room skim or managing a plastering contractor, you need two floats: a poly float and a fine sponge float. That's a total outlay under £20.
| Float type | Budget pick | Price | Quality pick | Price |
|---|---|---|---|---|
| Poly float (11"/280mm) | RST Poly Float (Toolstation) or Wickes own-brand | £4-5 | OX Pro Plasterers Float | £7-8 |
| Fine sponge float (11") | Wickes Sponge Float | £12 | Refina Fine Sponge Float (Screwfix, SKU 607RG) | £14 |
| Coarse sponge float | Not needed for skim plaster | - | Ragni Coarse Sponge Float (Toolstation) | £16 |
The budget poly floats are genuinely fine. There's no meaningful quality difference between a £4.58 RST float and a £7.78 OX Pro for a one-off project. Both have patterned non-absorbent faces and moulded handles.
For sponge floats, Refina is the brand the trade recommends. Across plastering forums, the consistent advice is to avoid Marshalltown sponge floats ("Marshalltown floats are crap mate, get one from Refina" is a direct quote from the Plasterers Forum, and it reflects wider trade sentiment). Refina is a UK manufacturer based in Poole, Dorset. Their sponge floats use 20mm natural rubber sponge on ABS plastic handles, and the fine grade at £13.99 from Screwfix is the one to buy for skim work.
Faithfull is the other budget brand you'll see. Their 11-inch poly float runs £6 – £7. Functional, but some users report cracking after extended use. Fine for a weekend project. Not one to keep in your toolkit long-term.
What about Speedskim?
The OX Speedskim is a wide flexible blade on a handle, sometimes grouped with floats in retailer listings. It's a different tool entirely. It's designed for flattening plaster across large areas in a single pass, and professional plasterers use it to increase their coverage speed.
Speedskim blades start around £50 for the 600mm semi-flexible version and run up to £80 for 900mm stainless flex blades. They have a steep learning curve (you need to round the blade edges with snips and sandpaper before first use, which OX doesn't mention in the packaging) and they're not worth the investment for a single DIY room. If you're plastering your entire house, different conversation. One room? Stick with a standard poly float and sponge float.
Alternatives
If the float-and-trowel approach feels like too much to learn for a single room, there are simpler options.
A plasterer charges £400 – £550 to skim a standard room (walls and ceiling), based on 2026 Checkatrade estimates. For a kitchen extension where you're already spending tens of thousands, paying a professional for a day's plastering is money well spent. Plastering is one of the few trades where the gap between professional and DIY results is immediately visible to anyone who walks into the room.
For small patch repairs (filling around new sockets, patching where a radiator was removed), a wide filling knife and ready-mixed filler will give acceptable results without any float work. It won't match a full skim finish, but for areas that will be behind furniture or kitchen units, it doesn't need to.
Where you'll need this
Plastering floats appear during the finishing stages of any extension or renovation project:
- Walls and blockwork - floating render coats on internal blockwork before skim
- Kitchen installation - patching plaster around new services and fittings
- Snagging checklist - checking plastered surfaces against flatness tolerances
Safety notes
Plastering floats themselves pose minimal risk. The hazards come from the materials you're working with.
Gypsum plaster is alkaline and will dry out and crack the skin on your hands after prolonged contact. Wear nitrile gloves or barrier cream. If you're sanding dried plaster (to fix mistakes), wear an FFP2 dust mask. Gypsum dust irritates the lungs.
Keep the floor covered with dust sheets. Wet plaster on a tiled or concrete floor is a genuine slip hazard, and dried plaster on timber flooring leaves marks that take real effort to remove.