UK scaffolding regulations explained: TG20, SG4 and the law behind them

What scaffolding regulations actually are

I get asked about scaffolding regulations every week, usually after someone has had a moody visit from an inspector on a wet Tuesday. The short version is simple. The law is the Work at Height Regulations 2005 and the Construction (Design and Management) Regulations 2015. TG20 and SG4 are not law. They are NASC guidance that shows one accepted way to meet the law on typical tube-and-fitting scaffolds and the way we build them without people falling.

If you stick within TG20 standard configurations and follow SG4 methods for erection, alteration and dismantling, most inspectors will nod it through because that is the benchmark they expect. Step outside TG20, or ignore SG4, and you can still comply with the law if you can prove your alternative is at least as safe. That proof is where drawings, calculations, and proper RAMS come in, not a shrug and a green tag stuck on a wobbly lift.

CDM 2015 matters because it sets out who is responsible for what. Clients and principal contractors must plan, appoint competent people and coordinate. Designers must eliminate and reduce risks, and not dump nasty surprises on the scaffolders. Contractors must manage the work safely. All of this sits on top of the Work at Height Regulations 2005, which require planning, competent people and suitable equipment for any work at height, scaffold included.

If you want a structured document to capture all of this, the Scaffolding RAMS Template UK | RAMS AI is a solid starting point for site-ready paperwork.

TG20 in practice, and what counts as compliant

TG20 is a practical recipe for tube-and-fitting scaffolds that fit within certain limits. Think typical façade scaffolds with standard bays and lifts, correct tie patterns, correct bracing and standard load classes as set out in BS EN 12811. You use the standard configurations and, if needed, produce a compliance sheet from current NASC guidance to show your scaffold design sits inside those rules. It is not a shortcut to ignore thinking. It is a way to avoid reinventing the wheel where the job is bread and butter.

On site that means no freelancing. If the TG20 compliance you planned calls for ties at set centres, you put the ties in, not “we will pop them in later when the brickies are gone”. Ledger bracing where shown, transom bracing where needed, proper base plates and sole boards that actually bear on something solid, not a part-buried kerb. Guardrails and toe boards to the right heights. Returns, inside boards and hop-ups only as allowed by the standard layout you are signed up to.

Changes that sound small can kick you out of TG20. Throw full sheeting or debris netting on, suddenly the wind loads go up and the safe tie pattern changes. Add a gantry over a shopfront, a bridge over a doorway or a cantilever lift to clear a conservatory, and you are not in standard territory any more. The same goes for hoists, loading bays beyond the standard arrangements, or foundations on ground that will not take the load. That is where a designer earns their keep.

For a deeper walk-through of method content and typical controls, see the Scaffolding RAMS Guide for UK Contractors | RAMS AI.

SG4 and stopping falls during scaffold operations

SG4 is about how you stop people falling while they build, alter or strip scaffold. It explains methods like sequencing from below, using advanced guardrails or 3T approaches so the leading edge is protected. The point is to have collective protection first and not rely on a bloke in a harness as the main control. This lines up with the Work at Height Regulations 2005, which push prevention and collective measures ahead of PPE.

On a cold morning with stiff fingers, the only thing between a safe lift and a nasty one is the habit of doing it the SG4 way. I see RAMS that say SG4 is followed, then photos of lads climbing outside the standards with a lanyard clipped to a spindly transom. That is not SG4. If the job needs harnesses for specific tasks, the anchors, lanyards and rescue plan must be part of the method, not scribbled in as an afterthought.

SG4 also covers practical bits that make the difference, like how you handle part-loaded lifts, how you board out progressively, and how you keep access routes protected as the build moves up and down. It is detailed for a reason. The mix of wind, wet boards and a rushed programme is when shortcuts creep in. An inspector will not argue with you about style. They will ask whether your method prevents a fall in line with the Work at Height Regulations 2005.

If your method relies on harness use, read Working at height rescue plans: why 'call 999' is not one and make sure the rescue is workable on your scaffold.

When TG20 is not enough and you need a bespoke design

Plenty of jobs sit outside TG20 and need a scaffold designer. Examples I see weekly include full sheeting or monoflex on exposed elevations, long bridges over entrances, truss-out scaffolds, cantilevered lifts to miss glass canopies, birdcages with odd grid spacing inside plant rooms, and chimney stacks that need spurs and plan bracing you will not find in a standard sheet. Public interfaces like fans, tunnels and debris protection over footways are almost always design items.

Loads push you into design too. Heavy loading bays, material hoists, long bays used as storage, or load classes that go beyond a standard TG20 arrangement all need proper calculations to BS EN 12811. Ground conditions are another trigger. Scaffolds founded on soft made ground, vaults, cellars or services need checks, spread solutions and sometimes groundwork, not wishful thinking and a couple of extra sole boards cut from old ply.

Odd geometry creates the next set of designs. Buildings with few tie options, curtain walling you must not drill, curved elevations, setbacks and step-ins, or mixing in system scaffolds and beams with tube-and-fitting. The Work at Height Regulations 2005 require suitable equipment and stability. CDM 2015 expects designs that reduce risks. A bespoke scaffold design is how you show the scaffold is strong enough, tied properly and buildable without exposing the team to daft risks.

Paperwork, handovers and the inspection rhythm

Paperwork is not the job, but it proves the job was done right. For TG20 scaffolds, keep your compliance sheet or layout, tie test records if used, and RAMS that match what got built. For designed scaffolds, carry the drawing, the calculations or design statement, any temporary works permits the principal contractor requires, and any special sequence or equipment requirements. When the scaffold is ready, a competent person should do a handover inspection and issue a handover certificate.

Inspections are not negotiable. Under the Work at Height Regulations 2005, scaffolds must be inspected before first use, after events likely to have affected stability such as high winds or vehicle strikes, and at intervals not exceeding seven days. Record those inspections in a scaffold register with the date, the person’s name, the structure inspected and any defects put right. I have rejected many RAMS because the inspection regime was one vague line at the end.

While tags are handy to show status at the access point, the legal record is the inspection report under the Work at Height Regulations 2005. If a lift is incomplete, make it obvious with brick guards, barriers or remove access ladders. If a bay is red tagged for a fault, do not let anyone strong-arm you into removing the tag before the defect is repaired. A tidy register and photographs of key tie locations save arguments later when trades start cutting things out.

What inspectors actually look for on site

You can tell a lot from the base. No proper sole boards on soft ground, standards sinking into asphalt, or base plates perched on edges of old paving flags will get you off on the wrong foot. I look for ledgers level and braced, transoms seated and secured, guardrails at the right height, toe boards that stop tools rolling, and access that does not force a climb on the outside. A green tag does not cancel a bad first impression.

Tie patterns are the next giveaway. Missing ties where the compliance said they should be, or ties bodged into rotten brickwork. Inside boards added without the right transoms or returns that break bracing lines. Loading bays made wider on site than the drawing shows, because someone fancied an extra pallet. I look up and see flapping debris netting turning the scaffold into a sail, with no change in the tie arrangement. That is a classic non-compliant setup.

Public interface is the final test. Where the scaffold touches a footway or a live site with other trades below, I expect toe boards, brick guards where there is risk of small items falling, fans or boarded fans where a route must be kept open, and signs and barriers that look like they are meant to be there. All of that sits under the Work at Height Regulations 2005 duty to prevent people being struck by falling objects and to keep the place safe for others.

RAMS that line up with TG20, SG4 and the law

A good scaffolding RAMS reads like the job, not like a cut-and-paste. It should identify the scaffold type and say whether it follows TG20 or a bespoke design. It should set the tie method, the loading arrangements, access and egress, and how you will manage interfaces like shopfronts or live roads. The method should reflect SG4 for erection, alteration and dismantling, and it should include controls for common site risks like overhead power, underground services at bases and public protection.

Under the Work at Height Regulations 2005, you also need a workable rescue plan where fall protection is used. Do not write “call 999” and think that will fly. Decide how you will get a suspended person down, who will do it, what kit is needed and where it will be kept. CDM 2015 expects cooperation and coordination, so your RAMS must align with the principal contractor’s traffic plan, permit system and temporary works procedures if they apply.

Finally, keep RAMS live. If the client asks for sheeting halfway through because the stone cutting is upsetting the neighbours, stop and revisit the design and tie pattern. If you uncover a cellar during base set out, do not carry on and hope. Update the risk assessment, speak to the designer or the principal contractor, and document the change. Inspectors want to see that the paper matches the tubes, not a pile of printouts that smelt faintly of cut cement board a month ago.

Questions we get asked

Is TG20 a legal requirement?

No. TG20 is NASC guidance, not law. The law is the Work at Height Regulations 2005 and CDM 2015. Most inspectors will accept TG20-compliant scaffolds as meeting the legal duties, because TG20 reflects current good practice for tube-and-fitting. If you choose another method, you must prove it is at least as safe.

When do I need a scaffold design instead of TG20?

You need a designer when your scaffold falls outside TG20 standard configurations. Common triggers are sheeting or netting, cantilevered lifts, truss-outs, long bridges, unusual ground, heavy loading bays or limited tie options. A bespoke design shows stability and strength to BS EN 12811 and helps you meet the Work at Height Regulations 2005.

How often do scaffolds need inspecting in the UK?

Under the Work at Height Regulations 2005, inspect before first use, after any event likely to have affected stability and at least every seven days. Record inspections in a scaffold register with details of who inspected, when, what was checked and any defects corrected. A tag at the ladder is not a legal record on its own.

Do I always need to wear a harness on scaffold?

No. The preferred approach is to prevent the fall in the first place using collective protection as set out in SG4 and the Work at Height Regulations 2005. Harnesses are used where collective measures cannot fully protect the person. If harness use is part of the method, you must specify anchor points and have a viable rescue plan.

Can I mix system scaffold with tube-and-fitting under TG20?

Mixing systems often takes you outside TG20’s standard configurations. Some small combinations may be fine, but many need a bespoke design to show the loads transfer correctly. If in doubt, ask a competent scaffold designer and document the arrangement so you remain within the Work at Height Regulations 2005.

The short version

UK scaffolding regulations come from the Work at Height Regulations 2005 and CDM 2015. TG20 and SG4 are NASC guidance that most inspectors treat as the benchmark for tube-and-fitting scaffolds and for preventing falls during scaffold operations. Use TG20 when the scaffold fits standard configurations. Bring in a scaffold designer when it does not.

Keep RAMS aligned with TG20 or the design, follow SG4 for methods, and stick to the inspection rhythm set by the Work at Height Regulations 2005. When weather, sheeting, geometry or loading changes, stop and revisit the design and the method. The tubes should match the paper, not the other way round.