MCS-I Concrete Screw Hanger

What an MCS-I concrete screw hanger is

The Mungo MCS concrete screw is screwed into a predrilled hole and its special thread cuts an internal thread into the concrete as it goes in, so it holds by mechanical interlock rather than expansion. The MCS-I is the version with an internal thread and a hexagon drive: instead of a head that clamps a fixture, it has a threaded body that takes threaded rod. Hobson gives the internal thread as M8 to M10, so it takes M8 or M10 threaded rod for suspending services.

Ours are size 6 (6mm nominal drill diameter, 7.5mm thread outside diameter per the ETA), zinc plated carbon steel, in two lengths. Hobson's descriptions give them as 6 x 35 and 6 x 55, which match the two nominal embedment depths, 35mm and 55mm, that ETA-16/0319 gives for size 6.

Which European Technical Assessment covers it

• •ETA-16/0319 (Mungo concrete screw MCS, MCSr and MCShr, sizes 5 and 6) lists the MCS-I with internal thread and hexagon drive (example MCS-I 6x55 IM M8/10) as one of its anchor versions. It is assessed only for multiple use for non-structural applications (ETAG 001 Part 6), for anchorages in prestressed hollow core slabs, and for anchorages with fire resistance requirements (not in hollow core slabs). Hobson's declaration of performance for sizes 5 and 6 refers to it.
• •Multiple use for non-structural applications means the service hangs from several anchors acting together, so if one anchor slips or fails, its load passes to the neighbouring anchors (Hobson's article on options in ETAG certifications). The ETA does not cover a service hung from a single MCS-I; the designer sets the number of fixing points.
• •ETA-16/0296 (Option 1, sizes 6 to 14) also shows the MCS-I configuration among its screw types, at size 6 embedments of 40 and 55mm. Its values for size 6 differ from ETA-16/0319, so an anchor design works to one ETA in full, not a mix of the two.
• •Both ETAs cover reinforced or unreinforced normal weight concrete of strength class C20/25 to C50/60, cracked and uncracked, and say anchorages are designed under the responsibility of an engineer experienced in anchorages and concrete work, with installation by appropriately qualified people under the supervision of the person responsible for technical matters on site.
• •Drilling: for size 6, both ETAs allow hammer drilled holes only (ETA-16/0296 also allows hollow drilling, but only for sizes 8 to 14).
• •Zinc plated MCS screws may only be used in dry internal conditions under the ETA.

MCS-I sizes and installation values

Both hangers are size 6 with an M8 to M10 internal thread; the length sets the embedment and everything that follows from it. Select a row to open that hanger in the selector.

Edge distance, spacing and member thickness

The minimums in the table are the closest an MCS-I may go to an edge or to another anchor, and the thinnest concrete it may go into. They are not distances at which it keeps its full capacity. ETA-16/0319 also gives the distances below which the concrete capacity starts to reduce: for concrete cone failure, an edge distance of 1.5 times and a spacing of 3 times the effective anchorage depth (27mm for the 35mm embedment, 44mm for the 55mm), and for splitting, an edge distance of 60mm and spacing of 120mm (35mm embedment) or 80mm and 160mm (55mm embedment). Closer than those, the engineer's design reduces the load per anchor.

In prestressed hollow core slabs (C30/37 to C50/60, size 6 only), ETA-16/0319 sets a minimum edge distance, anchor spacing and distance between anchor groups of 100mm each, keeps each anchor at least 50mm from the prestressing steel, and only covers slabs with a core distance of at least 100mm, a prestressing steel spacing of at least 100mm and a core width no more than 4.2 times the web thickness. It ties the characteristic resistance to the bottom flange thickness (1kN at 25mm or more, 2kN at 30mm, 3kN at 35mm, installation safety factor 1.2): these are characteristic values for the engineer's design, not safe loads. Its fire values do not apply in hollow core slabs.

Loads: why we do not quote a working load

The ETAs give characteristic values for an engineer's design (design method A), not working loads, and the two ETAs give different concrete pull-out values for size 6 at 55mm embedment. A characteristic value is not a safe load: it has partial safety factors applied in the design, and edge distance, spacing, member thickness, cracked or uncracked concrete and concrete strength all change it. So we do not publish a single load for these hangers, and the load per hanger, the spacing and the layout are for the services designer or engineer working to the complete ETA. The ETA covers multiple use only: the service hangs from several anchors so that if one slips or fails its load passes to its neighbours, not from a single MCS-I.

For fire design, ETA-16/0319 declares reaction to fire class A1 and gives characteristic steel resistances for fire resistance classes R30 to R120, with concrete failure modes calculated to EOTA TR 020 or CEN/TS 1992-4. Ask us and we will send the ETA and Hobson's declarations of performance for your engineer.

Zinc plated: dry internal conditions only

These are zinc plated. Hobson's finish comparison puts zinc plating at about 5 microns with low corrosion resistance, recommended for indoor and non-corrosive environments, and the ETA allows the zinc plated MCS only in dry internal conditions. ETA-16/0319 reserves external atmospheric exposure and permanently damp internal conditions for its A4 and HCR stainless screws, which are not in this range. For a carpark soffit open to the weather, a coastal site or anywhere damp, ask us for a fixing suited to that exposure.

How to install an MCS-I concrete screw hanger

1. Mark the positions from the services design, keeping to the minimum edge distance, spacing and member thickness in the table.
2. Hammer drill a 6mm hole to at least 40mm deep (35mm embedment) or 60mm deep (55mm embedment). Hammer drilling only.
3. Clean the dust out of the hole with a hand pump or blower.
4. Drive the MCS-I in with an impact screwdriver (maximum nominal impact torque 150Nm) or set it with a torque wrench to no more than 10Nm, until it reaches its full embedment and seats against the concrete. Ask us for the socket that suits the hexagon drive.
5. Check it: once set, it must not be possible to turn it any further, and the head must be undamaged (ETA). If it keeps turning, it has not gripped the concrete; do not hang anything from it.
6. Screw the M8 or M10 threaded rod into the internal thread and hang the service.

Concrete screw hangers in Adelaide

Allmat supplies MCS-I concrete screw hangers, XBolt PRO hangers, threaded rod and hole cleaning gear to electricians, plumbers, fire services and HVAC installers and builders across Adelaide and South Australia. Add the hangers to a quote with the rod and we will price the lot.

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