Summary
Patio repair and relaying is a different job from patio installation, and pricing it as if it were a fresh lay is one of the most common ways tradespeople lose money on it — or lose the job to a competitor who scoped it properly. This guide covers repair (fixing individual sunken, cracked, rocking or weed-infested slabs within an otherwise sound patio) and relaying (lifting the whole patio, or a substantial section of it, to renew the sub-base and bedding and reset the slabs). It does not cover laying a new patio from scratch — for that, see patio installation pricing guide.
Most repair and relay jobs exist because the original installation cut a corner. Spot-bedding — dropping slabs onto small mortar pads instead of a full mortar bed — is the single biggest cause of the sunken and rocking slabs that generate repair call-outs. Poor or reversed falls (water pooling towards the house instead of away from it) is the second most common driver, and it's the one with real consequences: standing water against a wall can breach the damp-proof course and cause damp inside the property. A patio that "just needs a slab or two re-set" often turns out, once you lift the first slab, to have no proper sub-base at all — which changes the job from a 30-minute repair into a relay.
The commercial reality of this trade is that customers frequently underestimate the job. They see one wobbly slab and expect a quick fix; you arrive, find the sub-base has washed out under half the patio, and now have an awkward conversation about scope creep. Setting the client's expectations at quoting stage — ideally after lifting a test slab to check what's underneath — avoids that conversation happening on-site after work has started.
Key Facts
- Spot-bedding is the leading cause of failure — slabs bedded on isolated mortar dots (rather than a full 35–50mm mortar bed) rock, sink, and crack within 2–5 years as the unsupported slab edges flex under load
- Reverse or inadequate falls are a damp risk, not just a puddling nuisance — water pooling against the building can breach the damp-proof course
- Minimum 150mm clearance below DPC — Building Regulations Approved Document C requires finished external ground/paving level to sit at least 150mm below the damp-proof course; a relay is the opportunity to correct historic non-compliance
- Recommended fall away from the building — trade good practice (not a fixed statutory percentage) is a minimum fall of around 1:80 (roughly 12.5mm per metre) directed away from the property, consistent with the general design principles in BS 7533
- Weed regrowth in joints usually signals joint failure, not just neglect — sand-only joints last 1–3 years before weed and moss recolonise; resin-bound polymeric jointing compound typically lasts 5–10 years+
- Porcelain slab lifting/hollow-sounding is commonly caused by missing or inadequate slurry primer at the original lay — porcelain needs a bonding slurry coat, not just a mortar bed, or it can debond
- A "quick fix" often isn't — lifting one sunken slab frequently reveals a washed-out or absent sub-base beneath the surrounding area, converting a spot repair into a relay
- Frost heave and tree root movement are common non-workmanship causes of sunken or displaced slabs, particularly on clay soils
- Breakage on lifting is normal, not a sign of poor practice — expect 10–20% breakage of existing slabs when lifting an older patio, especially concrete slabs more than 10–15 years old; budget for replacement or nearest-match slabs
- BS EN 124-1:2015 governs cover loading classes if the patio incorporates a drainage channel or gully cover being reset during the relay
- Waste duty of care applies — broken slabs, old bedding and hardcore removed from site are controlled waste under the Environmental Protection Act 1990 s.34; use a licensed waste carrier and keep the transfer note
- CDM Regulations 2015 apply even on small domestic jobs — the client's duties are usually passed to the contractor by default on domestic projects, but larger relays with multiple trades still need basic coordination
- Party Wall etc. Act 1996 can apply if excavation for relaying goes within 3m of a neighbour's foundation and below its depth — rare on a like-for-like relay but worth flagging on boundary patios
- Full mortar bed, not spot bedding, is the only acceptable repair specification — repeating the original mistake during a "repair" just delays the next failure by a year or two
- Existing slab match risk — older ranges are frequently discontinued; agree with the customer up front whether near-matches are acceptable or whether a full relay with new slabs is the better answer
Quick Reference Table
Spending too long on quotes? squote turns a 2-minute voice recording into a professional quote.
Try squote free →| Repair/relay type | Scope | Trade cost (materials + labour) | Typical quoted price |
|---|---|---|---|
| Single slab re-bed (rocking/settled) | 1 slab | £45–£105 | £90–£180 (minimum call-out often applies) |
| Cluster spot repair | 3–8 slabs, localised | £150–£350 | £250–£550 |
| Re-pointing/joint renewal only | Per m² | £4–£8/m² | £8–£16/m² |
| Small-area relay, sub-base renewed | Up to 10m² | £45–£70/m² | £70–£120/m² |
| Full patio relay, existing slabs reused | Whole patio | £55–£85/m² | £85–£150/m² |
| Add: partial slab replacement (10–20% breakage) | Whole patio | +£8–£20/m² | +£15–£35/m² |
| Falls correction as part of relay | Whole patio | Included in relay rate above | Included in relay rate above |
| Skip/waste disposal | Per job | £120–£220 | £150–£280 |
Detailed Guidance
Diagnosing the job before quoting
The most important step in pricing repair vs relay work is lifting a test slab (or two, in different areas) before quoting a fixed price. Look for: is there a proper compacted sub-base under the bedding, or bare soil; is the bedding a full mortar bed or spot dots; is there any sign of a washed-out void beneath adjacent slabs; and what direction is the fall running. A five-minute test lift turns a guess into an informed quote and protects you from under-pricing a job that turns out to need a full relay once you're on-site.
If the customer wants a fixed price without a pre-inspection, quote the repair on the assumption of a full mortar bed relay of the affected area and be explicit in writing that the price may change if the sub-base is found to be missing or inadequate.
Spot repair: re-bedding individual slabs
For a handful of sunken, cracked, or rocking slabs within an otherwise sound patio, the job is: lift the affected slab(s), clean off old bedding, check and top up the sub-base if needed, re-bed on a full mortar bed (not spot dots), relay to the correct level and fall, and re-point the joints. A single slab is rarely economic as a stand-alone call-out once travel and set-up are accounted for — most tradespeople apply a minimum call-out charge (£150–£220 quoted) that covers 1–3 slabs, with additional slabs priced incrementally.
Full relay: lifting, sub-base renewal, and re-laying
A full relay is justified when: the sub-base has failed across a significant area, falls need correcting throughout, more than roughly 20–30% of slabs are affected, or the patio was originally spot-bedded (meaning every slab is at risk, not just the visibly failed ones). The specification should match a proper new-build patio: excavate as needed, install or top up compacted Type 1 MOT sub-base to 100–150mm, lay slabs on a 35–50mm full mortar bed, and point with a weatherproof mortar or resin jointing compound. Correcting falls at this stage — resetting levels so water runs away from the building at a minimum 1:80 fall — is the single highest-value part of a relay and should be sold as such, not treated as an incidental extra.
Correcting drainage and DPC clearance
Where a patio has been laid up to, or above, the damp-proof course — a very common defect on older properties — a relay is the opportunity to drop the finished level and restore the 150mm minimum clearance required under Approved Document C. This sometimes means reducing the sub-base depth locally near the building or introducing a drainage channel (see drainage falls and gradients) at the building line to intercept run-off before it reaches the wall. Flag this clearly to the customer — it's a genuine defect with damp-risk consequences, not an upsell.
Weed regrowth and joint renewal
Where the slabs themselves are sound and the only issue is failed joints — weed and moss regrowth, sand washing out — this is a lower-cost, higher-margin job than a full relay. Rake out old sand joints, treat for weed regrowth, and re-point with a polymeric resin jointing compound for a longer-lasting result than sand. This is worth pricing and selling separately from a full relay; many customers with a tired-looking but structurally sound patio only need this.
Handling breakage and slab matching
Older concrete and natural stone slabs are brittle after years of weathering and will break during lifting at a higher rate than new stock — budget 10–20% breakage on a relay of a patio over 10 years old. Agree with the customer at quoting stage what happens if the exact slab is discontinued: nearest match, a mixed/random-lay pattern to disguise variation, or sourcing reclaimed stock at a premium. Don't leave this conversation until you're mid-job with a pile of broken slabs and no replacement plan.
Worked pricing example
A 20m² patio with 6 visibly sunken or cracked slabs, plus poor falls causing water to pool near the house wall across the whole area, needs a full relay rather than a spot repair.
Trade cost (materials + labour, before markup):
- Labour and materials (lift, sub-base renewal, full mortar bed relay, falls correction) at £70/m² midpoint × 20m² = £1,400
- Replacement slabs — allowing 15% breakage on ~56 slabs (600x600mm), roughly 8 slabs at £18 trade cost each = £144
- Skip and waste disposal = £180
- Total trade cost: £1,724
Quoted price to customer:
- Applying a typical 40% margin: £1,724 × 1.4 = £2,414, rounding to £2,400–£2,450 for the job.
This sits comfortably within the £1,900–£3,200 quoted range given in the Quick Answer for a full 20m² relay — the range accounts for variation in slab type, breakage rate, and access difficulty on other jobs.
Frequently Asked Questions
How do I know if a job is a repair or a full relay?
Lift a test slab in the worst-affected area and one in an apparently sound area. If both show a proper compacted sub-base and full mortar bedding with only localised failure, it's a repair. If either shows spot-bedding, a washed-out void, or bare soil under the bedding, price it as a full relay — the same defect is almost certainly present throughout, even where it hasn't visibly failed yet.
Can I reuse the existing slabs on a relay?
In most cases yes, provided they're not cracked, and you budget for breakage during lifting (typically 10–20% on older stock). Natural stone tends to survive lifting better than concrete slabs of the same age. Porcelain is the most breakage-prone during removal because it's thin and can shatter cleanly rather than crack.
Do I need planning permission or building control approval to relay an existing patio?
No — relaying within the existing footprint doesn't trigger planning permission or Building Regulations approval on its own, since you're not increasing impermeable coverage or creating a new structure. However, if the relay corrects a DPC clearance breach or a drainage defect, you're bringing the property closer to compliance with Approved Document C and H, which is a genuine selling point to raise with the customer even though it isn't a formal notifiable event.
What causes a patio to sink years after installation?
The most common causes are: spot-bedding failing under load, sub-base that was never properly compacted or was too thin, water washing out fines from beneath the slabs due to poor falls or a leaking nearby drain, tree root growth or die-back changing ground conditions, and frost heave on clay soils. A relay with a properly compacted Type 1 sub-base and full mortar bed addresses all of these except ongoing tree root movement, which needs separate investigation.
Should I quote per slab or per m² for spot repairs?
Per-slab pricing with a minimum call-out works better for genuinely isolated repairs (1–5 slabs). Once the affected area exceeds roughly 8–10 slabs or a clear cluster/zone of the patio, switch to per-m² pricing — it's more transparent to the customer and better reflects that you're effectively relaying a sub-section rather than fixing isolated points.
Regulations & Standards
Building Regulations Approved Document C (Site preparation and resistance to contaminants and moisture) — requires finished external paving/ground level to be at least 150mm below the damp-proof course
Building Regulations Approved Document H (Drainage and waste disposal) — governs surface water disposal and falls where a relay affects drainage routing
BS 7533 series (Pavements constructed of clay, precast concrete or natural stone flags/setts) — design and construction guidance for laid-flag pavements
BS EN 124-1:2015 — loading classification for any gully or channel drain covers reset during the relay
Environmental Protection Act 1990, s.34 — Duty of Care for the disposal of broken slabs, old bedding, and hardcore as controlled waste
CDM Regulations 2015 — health and safety coordination duties, including on domestic projects where duties typically transfer to the contractor
Party Wall etc. Act 1996 — may apply if excavation for relaying occurs within 3m of, and below the foundation depth of, a neighbouring building
Approved Document C: Site preparation and resistance to contaminants and moisture — GOV.UK
BS 7533 pavement design and construction standards — BSI Group
Duty of care for waste — GOV.UK, Environmental Protection Act 1990 guidance
patio installation pricing guide — pricing for a brand-new patio installation, not repair/relay
patio cleaning and sealing pricing guide — for patios where the slabs are sound and only cleaning/sealing is needed
patio laying — technique guide for correct sub-base, bedding and jointing specification
drainage falls and gradients — falls and gradient design referenced when correcting drainage during a relay