For large-format porcelain in the UK (for example 60×120 cm), British Standard guidance points to a cementitious adhesive rated at least C2 S1 under BS EN 12004, solid-bed fixed (BS 5385-3:2024). At Ark Tiles, Larsen’s manufacturer descriptions recommend Fibreflex Standard Set+ C2 S1, Fibreflex Rapid Set+ C2 S1, FiberFlex Semi-Rapid Set+ S1 and FIBERFLEX Ultimate Rapid Set S2. A 20 kg Fibreflex Standard Set+ grey bag is £12.29 (29 Sep 2026) and covers roughly 4–5 m² at a 3 mm bed (manufacturer data on the product page).
Prices checked 29 Sep 2026. Sale and list prices can change. Written by The Ark Tiles team.
What counts as a large-format tile?
BS 5385 describes a large-format ceramic tile as one with an area above 3,600 cm² and no edge longer than 1,200 mm. A panel is larger still: more than 1 m², or any edge longer than 1,200 mm. In UK shops the sizes people mean are more practical: 60×60 cm, 60×120 cm, and porcelain bigger than that. You will find those sizes in our floor tiles collection.
The same summary of BS 5385-3:2024 says large-format tiles should be fixed with at least a C2 S1 adhesive, in a solid bed, with the back of the tile buttered. Dispersion (ready-mixed) adhesives are not suitable for this work. That is a standards point, not a brand ranking.
C2, S1 and S2 in plain English
The letters on a bag come from BS EN 12004. C means the adhesive is cement-based. C2 means improved adhesion, a step up from a normal C1. S1 means deformable, the flexible class. S2 means highly deformable. Extra letters you will see: F for fast-setting, T for reduced slip on walls, and E for extended open time.
On our product pages, Fibreflex Standard Set+ grey is listed as C2TES1. That is cement-based, improved adhesion, reduced slip, extended open time, and S1 flexibility. FIBERFLEX Ultimate Rapid Set S2 grey is listed as C2FS2: improved cement adhesive, fast-setting, and highly deformable. Rapid Set+ grey is C2FS1. FiberFlex Semi-Rapid Set+ grey is C2TES1.
For large-format porcelain, the starting point in the BS 5385 summary above is at least C2 S1. S2 is for when the background is more demanding, which the next sections cover. Always follow the bed depth and coverage on the bag you buy.
Best adhesive for large-format tiles at Ark Tiles
We stock Larsen. The products below are the ones Larsen’s own descriptions recommend for large-format tiles, with the class, coverage and price taken from the live product page on 29 Sep 2026.
FiberFlex Semi-Rapid Set+ and FIBERFLEX Ultimate Rapid Set S2 are sold by the pallet only. There is no single 20 kg bag of either on the store, so there is no single-bag price. Where a “per bag” figure appears, it is the pallet price divided by the number of bags, not a bag you can buy on its own.
| Product | Class | Pack | Coverage and bed (manufacturer data) | Price on 29 Sep 2026 |
|---|---|---|---|---|
| Fibreflex Standard Set+ C2 S1 grey | C2TES1 | 20 kg bag | Roughly 4–5 m² per bag at a 3 mm bed. Bed 3–12 mm (up to 20 mm in small isolated areas). Grout after 18 hours. | £12.29 |
| Fibreflex Rapid Set+ C2 S1 grey | C2FS1 | 20 kg bag | About 4 kg/m² at a 3 mm bed (about 5 m² from a 20 kg bag). Bed 3–12 mm (up to 20 mm in small isolated areas). Grout after about 3 hours. | £14.39 |
| FiberFlex Semi-Rapid Set+ S1 grey | C2TES1 | Half pallet, 24 × 20 kg. Pallet only. | About 4 kg/m² at a 3 mm bed. Bed 3–12 mm (up to 20 mm in small isolated areas). Grout after 6 hours. | £352.51 (about £14.69 a bag from the pallet price) |
| FIBERFLEX Ultimate Rapid Set S2 grey | C2FS2 | Half pallet, 24 × 20 kg. Pallet only. | About 4 kg/m² at a 3 mm bed. Bed 3–6 mm (up to 12 mm in small isolated areas). Grout after 3 hours. | £482.40 (about £20.10 a bag from the pallet price) |
| Fibreflex Standard Set+ C2 S1 grey full pallet | C2TES1 | Full pallet, 48 × 20 kg | Same as the single bag. | £589.82 |
| Fibreflex Rapid Set+ C2 S1 grey half pallet and full pallet | C2FS1 | 24 or 48 × 20 kg | Same as the single bag. | £345.31 half pallet, £690.62 full pallet |
Shop the full range in tile adhesives, or buy by the pallet from trade pallet deals. Half and full pallets are delivered kerbside with a tail-lift.
Standard set, rapid set or S2?
Fibreflex Standard Set+ is the longer-working option. The product page lists an extended open time and grouting after 18 hours. Choose it when you need time to place large tiles and still hit full coverage.
Fibreflex Rapid Set+ is the same S1 class in a faster set. The page says you can grout after about 3 hours, with a bed of 3–12 mm. Choose rapid when the floor needs to be grouted the same day. The working time is shorter, so mix only what you can use.
FiberFlex Semi-Rapid Set+ sits between them. Larsen’s description aims it at very large-format tiles: a longer pot life, then grouting after 6 hours, bed 3–12 mm. It is pallet-only on our site.
FIBERFLEX Ultimate Rapid Set is the S2. Larsen’s page positions it for porcelain, natural stone and large-format tiles, including difficult substrates (see the product page). Grout after 3 hours. The bed is 3–6 mm, or up to 12 mm in small isolated areas, which is thinner than the S1 bags. It is also pallet-only. For many stable screeds, C2 S1 is the usual starting point.
Coverage and how many bags
Use the manufacturer figure as the baseline, not a guess at your floor.
A 20 kg bag of Fibreflex Standard Set+ grey covers roughly 4–5 m² at a 3 mm bed. Fibreflex Rapid Set+, FiberFlex Semi-Rapid Set+ and FIBERFLEX Ultimate S2 each list about 4 kg/m² at a 3 mm bed on their product pages.
Those 3 mm figures are the manufacturer baseline. Large-format floors usually need a thicker bed and back-buttering, so allow extra bags. Level the floor first where it is not flat enough: see self-levelling compound, the levelling compound calculator, our SLC1550 drying and coverage guide and the best self-levelling compound UK guide.
Free UK delivery over £499. Prices above were checked on 29 Sep 2026.
Fixing tips that affect adhesive choice
Coverage on the bag assumes the adhesive is used as the manufacturer describes. For large-format tiles, the BS 5385 summary cited above calls for a solid bed and back-buttering, not a few dabs. Spots of adhesive leave hollows, and large tiles show them.
The floor needs to be flat before you start. If it is not, a self-levelling compound is the usual first step, then a C2 S1 or S2 adhesive. Dispersion adhesives are the wrong class for large-format tiles, again from that BS 5385 summary.
Levelling clips are a fitter’s choice. Follow the instructions on the bag for mixing, bed depth and open time rather than a general method. If you are unsure which of the four Larsen options fits the substrate, ask your tiler and read the product page.
FAQs
What is the best tile adhesive for large format tiles in the UK?
Look for a cementitious C2 S1 adhesive, or S2 where the background needs it, and fix in a solid bed. At Ark Tiles, Larsen’s manufacturer descriptions recommend Fibreflex Standard Set+ C2 S1, Rapid Set+ C2 S1, FiberFlex Semi-Rapid Set+ S1 and FIBERFLEX Ultimate Rapid Set S2 for large-format tiles. Follow the bag for bed depth and coverage.
What do C2, S1 and S2 mean?
Under BS EN 12004, C means cement-based and C2 means improved adhesion. S1 is deformable (flexible). S2 is highly deformable. Extra letters: F is fast-setting, T is reduced slip, E is extended open time. Fibreflex Standard Set+ is listed as C2TES1. Ultimate Rapid Set is listed as C2FS2.
How much tile adhesive do I need for large-format tiles?
A 20 kg Larsen Fibreflex Standard Set+ covers roughly 4–5 m² at a 3 mm bed. Large-format floors usually need a thicker bed and back-buttering, so allow extra bags. Fibreflex Rapid Set+, Semi-Rapid and Ultimate S2 list about 4 kg/m² at 3 mm on their product pages.
Rapid set or standard set for 60×120 tiles?
Standard Set+ gives a longer working time and can be grouted after 18 hours. Rapid Set+ is ready for grouting in about 3 hours (manufacturer data). Choose rapid when you need to grout the same day. Choose standard when you need more time to place large tiles.
When do I need S2 adhesive?
Use S2 when the substrate is more demanding. Larsen positions FIBERFLEX Ultimate Rapid Set S2 for porcelain, natural stone and large-format tiles, including difficult substrates (see the product page). For many stable screeds, C2 S1 is the usual starting point.
Can I buy tile adhesive by the pallet?
Yes. These lines come as 24-bag half pallets or 48-bag full pallets, with kerbside tail-lift delivery. Free UK delivery over £499. See trade pallet deals. Semi-Rapid Set+ and Ultimate S2 are pallet-only. Standard Set+ and Rapid Set+ are also sold as single 20 kg bags.
Do I need to level the floor before large-format tiles?
Large-format tiles need a flat base. If the floor is uneven, use a suitable self-levelling compound first, then fix with a C2 S1 or S2 adhesive. See self-levelling compound and the levelling calculator.
Can I see tiles before I buy the adhesive?
Order free cut-size samples of indoor tiles, laminate or LVT. The sample is £0, delivery is £4.99 per order, and you can order up to 5. Paving samples are not available. Or visit the showroom at Unit B2, Stag Industrial Estate, Endemere Road, Coventry CV6 5PY, Monday to Friday 9–6 and Saturday 10–5, closed Sunday. Phone 0330 520 1804. Start at free cut-size samples.
Shop adhesive or visit Coventry
Browse tile adhesives or trade pallet deals. Level first with self-levelling compound if the floor needs it. See full-size tiles at the Coventry showroom, Unit B2, Stag Industrial Estate, Endemere Road, CV6 5PY, Monday to Friday 9–6, Saturday 10–5, closed Sunday, or call 0330 520 1804. Free UK delivery over £499.
The Ark Tiles team
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