How to Tie a Scaffold to a Building: Anchors, Eye Bolts and Spacing
A scaffold tie is the connection between the scaffold and the building, and its job is to stop the structure moving either away from the wall or into it. Once a scaffold goes above roughly three times its base width, or once you sheet it, ties are no longer something you add if there's time. They are what holds the thing up.
Two decisions sit inside every tie, and they get muddled constantly. One is what goes into the wall. The other is what clamps onto the tube. Getting the second right is easy. Getting the first right is where scaffolds fail.
The question we field most often about anchor tubes isn't about strength at all. It's which length to order, from someone standing in front of a wall with 90 mm of insulation on it, wondering why the 300 mm tube they bought doesn't reach anything solid. So that's where this starts.
What a tie is actually resisting
Wind doesn't only push a scaffold against a building. It pulls. A gust that hits the face of the building sheers up and around it and drags at the scaffold on the way past, and a sheeted scaffold catches that load the way a sail does. Ties have to work in tension and in compression, which is why a length of rope, a ratchet strap or a bit of banding is not a tie. Those only pull.
There's a second job that gets less attention. Ties shorten the effective length of the standards, which stops them buckling sideways under vertical load. A properly tied scaffold is carrying weight better, not just standing still better.
When ties stop being optional
Free-standing scaffolds live inside the 3:1 ratio, and we've written about what the 3-to-1 rule for scaffolding covers and where it stops applying. The short version: past that ratio the base can no longer do the work on its own, and the building has to take some of it.
Sheeting and netting change the sums earlier than people expect. A bare tube-and-fitting scaffold is mostly holes, and wind goes through it. Wrap it in debris netting and you've built a partial sail; wrap it in solid tarpaulin and you've built a full one. The tie pattern for a sheeted scaffold isn't the bare pattern with a couple more thrown in. It's a different design, and that design comes from whoever is responsible for the scaffold, not from a blog.
The four ways a tie grips
| Tie type | How it holds | Drilling? | Where it works |
|---|---|---|---|
| Through tie | A tube passes through an opening and is boxed against the inside face with a second tube. | No | Window and door openings. The opening has to stay unglazed while the scaffold is up. |
| Box tie | Tubes frame completely around a column, pier or return so the tie can't slide off. | No | Columns and piers with access on all four sides. Strong, and no holes in anyone's brickwork. |
| Anchor tie | A ring or eye bolt fixed into the structure takes a hooked tube back to the scaffold. | Yes | Blank walls with nothing to box or pass through. The most common tie on a domestic job, and the one that needs testing. |
| Reveal tie | A tube is jacked across a reveal with a screw pin and holds by friction alone. | No | Openings, as a supplement. Friction fixings loosen, so they're limited to a proportion of the total and checked often. |
Through ties and box ties are mechanical. Nothing relies on the strength of a hole. If the building gives you a column or an unglazed window, use it: no pull test is as convincing as a tube that physically cannot come out.
The hardware, part by part
An anchor tie is three items, and each one is chosen for a different reason.
The eye bolt and its plug. Our scaffolding eye bolts run from 90 mm up to 500 mm, galvanised, starting around € 2.16, and they pair with a Ø14 × 70 mm nylon wall plug sold in boxes of 100. Length is not a strength choice, it's a geometry one. Measure what sits between the outside face and the structural masonry: render, insulation, cavity closer, whatever is there. Add that to the embedment depth the plug needs, and the eye still has to stand proud far enough for a hook to seat properly. A 90 mm bolt into a wall with 90 mm of external wall insulation on it is anchored to polystyrene.
The anchor tube. The wall tie anchor tube with hook comes in 300, 400, 500, 600, 800 and 1000 mm, hot dip galvanised, € 6.66 to € 14.50. The length you want is the distance from the wall face to the inside standard plus enough tube past it for the coupler to grip properly. Too short and you end up couplering right at the tube end, which is exactly where a coupler's grip is worst. Too long and you've got a spear sticking into the working platform at shin height.
The coupler. The tie tube gets fixed to the scaffold with a load-bearing right angle coupler, from € 4.92 in our scaffolding couplers range. Not a single coupler, not a putlog coupler. Those are designed to hold a transom in place, they aren't classified for load, and a tie is the last place in the structure to find that out. Two couplers per tie is usual practice, taking the tube to both the inside standard and a ledger.
The numbers a designer works to
Tie capacity is where honest suppliers go quiet. It's worth explaining why, rather than inventing a figure.
The UK scaffolding federation's TG20 guidance sorts ties into three duty classes by working load in pure tension: light duty at 3.5 kN, standard duty at 6.1 kN and heavy duty at 12.2 kN. Its companion document on anchorage systems, TG4, sets the proof test at 1.25 times the working load, so a standard duty tie is tested to 7.6 kN. Across Europe the performance requirements sit in EN 12811-1, and a compliant scaffold design will state the class and pattern it assumes. Those are the figures a scaffold designer builds a pattern from.
What we will not do is print a kilonewton rating next to an eye bolt. The capacity of a drilled anchor is a property of the anchor, the plug and the material it's fixed into, taken together. The same bolt in dense engineering brick and in 1890s lime-mortared soft red brick are two completely different fixings, and only one of them is going to hold 6.1 kN. Anyone quoting you a fixed load for a wall they've never seen is selling, not advising.
Testing, which is the step that gets skipped
Drilled anchors get tested twice in principle. A preliminary test on sacrificial anchors in the actual wall tells you what that substrate will give, before the pattern is fixed. Then a proportion of the installed anchors get proof tested with a calibrated pull tester to the figure the design calls for, and the results get written down against positions.
Three things go wrong in practice. Testing gets done on the good wall and assumed for the bad one, when it's the soft patch of blockwork round the back that matters. Records get kept loose, and then nobody can say which anchors on a six-week job were ever tested. And anchors get proof tested to a number someone remembered rather than the number the design specified, which is worse than no test at all, because now there's a certificate saying it's fine.
On a commercial job none of this is optional. On a domestic one that nobody will ever inspect, it's still the difference between a scaffold that holds through a February gale and one that doesn't.
Pattern, spacing and the temptation to move one
The tie pattern comes out of the design, or the TG20 compliance sheet for the configuration you've built. It isn't a rule of thumb, and the spacing that was right on the last job is evidence of nothing about this one. What's worth knowing as a buyer is how many ties a pattern eats, because that's what you're ordering: they recur at intervals up the scaffold and along it, corners and returns need their own, and the top lift is not a place to be economical.
The habit worth breaking is moving a tie to get something past. A tie comes out, the delivery goes in, the tie goes back "later". Later is how scaffolds end up standing through a weekend of wind with a hole in the pattern. If a tie genuinely has to come out, something replaces it before it does, and that swap belongs to whoever is responsible for the scaffold.
Common questions
Can I tie into external wall insulation?
Not into the insulation, no. The anchor has to reach and embed into the structure behind it. That's the whole reason we stock eye bolts up to 500 mm. Measure the build-up before you order, and remember the sleeve through the insulation needs to keep the bolt from crushing it.
Can eye bolts and plugs be reused?
The bolt often can, if it isn't bent or corroded and the thread is clean. The hole usually can't: it has already moved under load, and a fresh plug in an old hole is not a fresh fixing. Drill new, and never re-use a position that failed a test.
How many reveal ties can I use?
Fewer than you'd like. They hold by friction, friction relaxes as the building moves and dries, and the standards treat them as a limited supplement rather than a primary tie. If your pattern is mostly reveal ties, the pattern is the problem.
Does galvanising matter on tie hardware?
More than on most fittings. Ties sit against a damp wall for the whole life of the scaffold, often in the splash zone, and they're the last components you want thinning. Our anchor tubes are hot dip galvanised for that reason. Electroplated zinc on a permanently wet component is a false economy.
What to order
Per tie position on a solid wall: one eye bolt sized to the wall build-up, one nylon plug, one anchor tube long enough to reach past the inside standard, two right angle couplers. If the wall has anything on its face, order the bolts a size longer than you think. A bolt 40 mm too long is an annoyance; one 40 mm too short is scrap.
Everything here ships from our warehouse in Eindhoven across Europe, and if you're working out quantities for a full lift, the scaffolding material range has the couplers, base jacks, netting and boards in one place. Tell us the wall build-up and the bay dimensions when you order and we'll tell you which eye bolt length actually fits.
