Insulation Fixing

What insulation fixings do

An insulation fixing (insulation plug) has a wide plate on its head that holds insulation board against the wall behind it. The MDD-CE and MDD-S fixings are nailed-in plastic anchors: the sleeve goes through the board into a hole drilled in the wall, and a nail driven down the sleeve expands it in the hole. The metal insulation nails, the MDI plug and the loose discs are other types, listed below. Insulation fixings are used for external insulation with render, often called ETICS or EIFS, such as polystyrene (EPS) render board on concrete and masonry walls.

The approvals for the MDD-CE and MDD-S fixings say what they are for: only as multiple fixings for bonded external insulation with render, in concrete and masonry, and only to carry wind suction. They must not carry the dead load (weight) of the insulation system: that is carried by the adhesive bond of the system to the wall. Design of the fixings is done to the European guideline ETAG 014 by an engineer experienced in anchorages, from the loads, the base material, the insulation thickness and the tolerances.

Insulation fixing types we carry

Hobson's documents give approval data for MDD-CE and MDD-S only, and those approvals as Hobson links them were printed valid to 2017 (MDD-CE) and 2018 (MDD-S), so we use them for installation data only, not as a current approval. For the other types, Hobson lists the name, material and plate size, so use them where the insulation system maker's fixing schedule names them. Select a row to open that type, then pick the length.

MDD-CE and MDD-S drill size, embedment, edge distance and spacing

From the two European technical approvals Hobson links for these fixings. MDD-CE: 10mm drill (cutting diameter no more than 10.45mm); for base materials in use categories A, B and C (concrete, solid and hollow masonry) drill at least 35mm deep for at least 25mm effective embedment, for category D (lightweight aggregate concrete) at least 50mm for 40mm, and for category E (autoclaved aerated concrete) at least 70mm for 60mm. MDD-S: 8mm drill (cutting diameter no more than 8.45mm), hole deeper than 35mm, effective embedment at least 25mm; its approval covers categories A, B and C only, which include lightweight concrete solid and hollow blocks and solid bricks (masonry units; see the drilling method below). Concrete must be at least C12/15, and masonry must match the brick or block types, densities and strengths listed in the approval.

Both approvals give the same minimums: 100mm spacing between fixings, 100mm from an edge, and a wall (base material) at least 100mm thick. The effective embedment is measured in the wall itself: Mungo's fastening dictionary notes that layers such as plaster, flagstones and insulating materials do not count towards the setting depth.

Drilling method matters. The MDD-S approval allows only rotary drilling (no hammer) in vertically perforated clay brick and lightweight concrete solid or hollow blocks, unless job site tests show hammer or impact drilling is acceptable. The MDD-CE approval allows rotary-impact drilling in concrete and in clay and calcium silicate brick, and rotary drilling in the other masonry it lists. For concrete or masonry of the approved categories that the approval gives no value for, such as other bricks or blocks, the characteristic resistance is found by at least 15 pull-out tests on site, carried out or supervised as the approval sets out. Job site tests do not extend the approvals to other wall materials such as timber or sheet.

Install at 0°C or above. For MDD-S the approval also limits exposure of the plate to sunlight to 6 weeks before it is covered by render, and asks for the fixings to be stored in their light-proof packaging, not extremely dried or frozen.

Hobson links the approvals as issued: ETA-12/0298 for MDD-CE (issued 28 June 2012, valid to 22 May 2017 as printed) and ETA-13/0727 for MDD-S (issued 20 June 2013, valid to 18 April 2018 as printed). Both are past their printed validity, so we give their installation data only and do not present either fixing as currently approved. Where a job needs a current approval, the designer or the insulation system maker specifies the fixing.

What length insulation fixing do I need?

The approvals give the rule: the fixing length must be at least the insulation thickness, plus any adhesive, levelling layer or old render between the board and the wall, plus the effective embedment in the wall. So the thickest insulation a fixing can hold is its length, less the embedment, less that layer. The table works out the length less the embedment for each length we carry; take the adhesive or levelling layer off that figure. Example from the MDD-S approval: a 135mm fixing with a 10mm layer and 25mm embedment holds up to 100mm of insulation.

How MDD-CE and MDD-S fixings go in

1. Check the wall is a base material the approval covers and that the fixing pattern and number come from the design or the insulation system maker.
2. Drill through the board into the wall with the right drill size, depth and drilling method (rotary only where the approval says so), keeping 100mm from edges and between fixings.
3. Push the fixing through the board until the plate sits on the board.
4. Drive the nail in to expand the sleeve in the hole.
5. Install at 0°C or above, and render over MDD-S plates within 6 weeks of sunlight exposure.

Plastic, zinc plated or stainless

The MDD-CE, MDS, MIP and MIS fixings are all plastic. The metal insulation nails come zinc plated (MIDS, MIDS-K) or 304 stainless (MIDSR, A2). Mungo's fastening dictionary says zinc plated steel anchors are for indoor use, not wet rooms, and that external use, wet rooms, high humidity and sites close to the sea need A4 (316) stainless. So use MIDS and MIDS-K indoors only, and do not use the 304 MIDSR nails on exposed, humid or coastal walls either: there, use the fixing the insulation system maker specifies and ask us about a 316 option.

Wind and fire

Wind: the MDD-CE and MDD-S approvals are for wind suction loads only, as multiple fixings, designed by an engineer; their characteristic values depend on the base material and are in the approvals. Hobson gives no wind data for the other types on this page.

Fire: the documents Hobson links for these fixings give no fire rating or reaction to fire classification for them. The fire performance of an external insulation and render system is a matter for the system maker, the designer and the building certifier, so do not treat any fixing on this page as fire rated.

Insulation fixings in Adelaide

Allmat supplies insulation fixings, insulation nails, discs and masonry drill bits to renderers, cladding installers and builders across Adelaide and South Australia. Add the fixings to a quote with your drill bits and other fixings, and we will price the lot.

Questions