Wedge, Sleeve and Screw Anchors in Concrete: What You Can Decide Before the ETA/ICC-ES Report Arrives

Cracked-concrete approval is granted per product and per size

A cracked-concrete rating is not a property of an anchor family. It is granted product by product and size by size, so a rating you have seen on one diameter of a wedge anchor tells you nothing about the next size up. And nothing about a sleeve or screw anchor from the same catalogue ¹⁹. The assessment route also splits by how the anchor is used. Concrete screw anchors are assessed for single use under EAD 330232, because de-installation and re-installation may damage the screw. Products intended to be loosened and retightened fall under EAD 330011 instead ¹⁹. That distinction matters before you compare anything else: an anchor you plan to back out and re-torque is being assessed against a different document than one you drive once and leave. So the first thing to establish is not which family performs better, but which specific product-and-diameter combination holds the approval for your substrate. Ask for the ETA or ICC-ES report naming the exact diameter, and check the cracked-concrete column in it.

Substrate state decides eligibility before load comparison means anything

If the concrete is cracked or expected to crack, the cracked-concrete qualification is a gate: an anchor without it is out, regardless of how its load figures compare. That is why the substrate state comes before any capacity discussion — it removes options rather than ranking them. Where the sources do offer a comparison, it is directional only. One vendor source places mechanical expansion anchors (wedge, sleeve, drop-in) slightly above a comparable concrete screw anchor on characteristic tension in cracked concrete. And reports concrete screws at 9–16 kN in cracked C20/25 at an effective embedment of 64–85 mm ¹⁹. That is a single supplier's band, not an industry limit, and it is stated for one concrete class and one embedment range. Treat it as an order-of-magnitude signal, not a design value. The reduced cracked-concrete load value you actually design to has to come from the product's own approval document. Family-level comparisons cannot substitute for it, because the approval is issued at product-and-size level ¹⁹.

Setting a preliminary edge distance and spacing for layout

For early layout you need a number, and general fastener design practice gives one: a nominal edge distance of 2D from the hole centreline, a minimum edge distance not less than 1.5D. And a nominal spacing between fasteners of 4D, where D is the fastener diameter ³. A separate guideline agrees on the 2× diameter figure for spacing and edge distance, aimed at preventing cracks ¹⁸. Use that as a starting point, not a design value. The 2D/1.5D/4D figures are general fastener guidance, not concrete-anchor values, and the capacity-reduction curve that applies below the full-value threshold has to be read from the product's approval document. What the sources do not give you is the point at which reduction begins for a specific anchor, or how steeply it falls. One practical consequence: if your layout cannot achieve the nominal figure, you are not choosing between anchors on load tables any more . You are checking whether the product's approval still covers the reduced edge distance you can actually build.

Hole tolerance and drilling method control the achieved capacity

For mechanical expansion anchors, sensitivity to hole tolerance is identified as the governing risk ¹⁹. That makes the drilled hole — not the anchor catalogue — the variable that decides whether you get the tested capacity. The mechanism is straightforward: an expansion anchor develops its hold by pressing against the hole wall, so a hole drilled oversize or with the wrong bit gives the expansion less to bite on. Concrete screw anchors carry their own installation conditions. They require rotary-hammer drilling only, with the bit diameter the approval calls for, and hole cleaning remains a tested variable ¹⁹. Note that the bit is not the nominal screw diameter — each screw size uses its own smaller bit, so a 1/4″ screw takes a 3/16″ bit rather than an 8 mm one ¹⁹. Before you rule an anchor in, confirm you can control the drilling method and bit diameter on site. If the crew cannot guarantee the specified bit or the cleaning step, that is a reason to rule the product out rather than to hope the capacity holds.

Coating follows exposure, and the joint is the system

Exposure maps to coating class in a way that is consistent across the general guidance: zinc-plated steel for indoor and dry service, hot-dip galvanized for outdoor exposed work. And stainless for coastal or chemical exposure ¹³. The thickness gap behind that mapping is large — hot-dip galvanized fasteners carry 43–86 µm of zinc depending on diameter, against up to 25 µm for zinc plating. And the zinc layer protects the steel sacrificially rather than only as a barrier ⁷. Stainless is not automatically the safer choice. In an aluminium housing exposed to salt, a stainless screw can form a more aggressive galvanic pair than zinc-plated steel if the joint is not isolated ⁸. In marine, road-salt, fertilizer, mining and washdown service, metal compatibility alone is rarely enough. The joint needs a compatible base material, protective coating where appropriate, electrical isolation, sealed interfaces and geometry that does not trap moisture ⁸. For a concrete fixing, that means checking the anchor, the base material and the fixture as one assembly. Coating name alone will not tell you whether the joint survives.

Relative material cost ranks the families; absolute price does not

On relative material cost, concrete screw anchors come out lowest among the three families, mechanical expansion anchors (wedge, sleeve, drop-in) are low-to-medium, and chemical anchors are higher ¹⁹. That ranking is useful for early budgeting and for deciding whether a screw anchor is worth pursuing before you spend time on approvals. It is a ranking only. No source in this set gives a cost per anchor, a diameter or length availability list, a lead time, or a volume threshold at which pricing changes. Those have to be quoted against your actual schedule and quantities rather than assumed from the family.

Pre-RFQ checks that push the missing data onto the supplier

The sources establish the decision sequence but not the anchor-specific figures, so each check below is something you obtain from the product's approval document rather than something you can settle from a family comparison.

• Request the ETA or ICC-ES report for the exact product and diameter, and confirm the cracked-concrete qualification in it ¹⁹.
• Confirm whether the product is assessed for single use (EAD 330232) or for loosening and retightening (EAD 330011) ¹⁹.
• Ask for the reduced cracked-concrete load value from that report, not from a family comparison ¹⁹.
• Confirm the approval-listed bit diameter and that rotary-hammer drilling is the specified method ¹⁹.
• Ask what hole cleaning the approval requires and how it will be verified on site ¹⁹.
• Ask for the capacity-reduction curve below the full-value edge distance and spacing threshold ^{3, 18}.
• Confirm the coating class against the exposure, and whether the joint needs isolation from the fixture material ^{13, 8}.

Where the sources disagree

Two open points remain, and both are worth resolving before you commit to a figure or a material.

FAQ

Related pages

• Anchors product page
• Screws product page
• Surface finishes product page
• Cold Heading vs Machining for Fasteners: How to Choose a Route on Strength Class, Coating and Qualification Evidence
• Screw Family Selection by Base Material: Wood, Machine and Self-Tapping Threads, Engagement and Coating