Can you glue carpark insulation to the soffit instead of fixing it?

We use adhesive on every job, but alongside the anchors rather than instead of them. On polyester it is a contact adhesive laminated to the slab so the panel pulls up flat; on Kingspan Kooltherm it is a construction adhesive that does not attack the phenolic core, in large dollops. Adhesive-only fixing is the narrow case: GreenStuf ASL permits it in certain applications, Mammoth only where steel in the concrete stops a penetration, and the two rigid boards publish no adhesive method at all.

How many anchors does each carpark soffit system need?

Eleven per 2400 by 1200 panel for GreenStuf ASL and Kingspan Kooltherm K10. Eleven to twelve for Mammoth. Five to six for GreenStuf Phenolic Foam Board. GreenStuf ASL sets maximum 600mm centres, 100 to 200mm from the panel edge. Kingspan asks for 50 to 150mm from the edge and a minimum 35mm head diameter. The schedules are not interchangeable.

Can you fix into a post-tensioned slab?

Yes, and it is routine work for us. The tendons are the constraint, not the concrete, so we scan and mark first and set the panel layout around what we find. Shot-firing blind is the thing to avoid, because a strand struck under load fails along its length. WorkSafe requires advice from the designer on fastener placement in post-tensioned structures, and a shot-fired anchor embeds 24 to 29mm at a depth you cannot adjust, so where cover is tight a drilled pin is the answer. Tell us at quote stage if any level is post-tensioned. It changes the method and the rate.

Does using a different fixing method void the insulation warranty?

Generally yes. All four make the warranty conditional on installation to the manufacturer's instructions, so a non-compliant install means the warranty never engages rather than being weakened. Kingspan is the most explicit: clause 12 of their April 2026 warranty statement rules out liability where the installation requirements have not been met.

How soon after the pour can you fix insulation to a slab?

Seven days is the working answer. Hilti's guidance is not to fire anchors into concrete poured on site until it has cured 7 days unless testing proves it will hold, and to base holding capacity on the strength on the day rather than the 28 day figure. A slab at ten days might be at 20 to 25 MPa where the drawing says 40, which is inside the window for some fasteners and under the floor for others. So we ask when the pour went down before we commit to a start date.

Insulation anchors fixed through soffit panels to a concrete carpark slab

Carpark Soffit Fixings & Adhesives

Fixed to the manufacturer's schedule.

So the warranty you paid for holds.

Every schedule compared
Post-tensioned slabs
Green concrete
Supply and install

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Carpark soffit fixings and adhesives, supplied and installed to every manufacturer's published schedule. Anchors, adhesive and tape priced into one rate, on concrete slabs, post-tensioned slabs and slabs already full of services.

Auckland based, nationwide

We go where you need us, so you get the same crew wherever the next project is.

Programme focused

We work backwards from your schedule and resource the job accordingly.

QA & PS3 supplied

A QA package and completion documentation at handover, under a 5 year workmanship guarantee.

SiteWise Green 2026/27

Prequalified through Site Safe, so we clear main contractor onboarding before we quote.

The fixing is the part nobody prices

A carpark soffit package gets priced on the panel, and the panel is the easy part. What decides whether the job goes well is the fixing: how many, into what, and whether the slab you have is the slab the drawings promised.

Get it wrong and it does not show up on handover day. It shows up in a year, when a bay has dropped, the level is live and the scaffold is long gone. Every manufacturer ties its warranty to the fixing schedule, so a short-fixed soffit is not a weakened warranty. There is no warranty.

We have fixed every one of these systems, on green slabs, post-tensioned slabs and slabs full of services. Here is what each manufacturer asks for.

How many fixings does carpark soffit insulation need?

Each manufacturer publishes only their own schedule, and side by side they do not agree. A pattern that is right on one product is wrong on the next, which is why we confirm it against the specified product before we price.

Published fixing schedules for the four carpark soffit systems on the New Zealand market
	GreenStuf ASL	Mammoth Carpark Panel	Kingspan Kooltherm K10 G2	GreenStuf Phenolic
Board size	2400 × 1200mm, 2.88m²	2400 × 1200mm, 2.88m²	2400 × 1200mm, 2.88m²	1000 × 1200mm, 1.20m²
Fixings per board	11	11–12	Minimum 11 (3.81/m²)	5–6
Maximum centres	600mm	Not stated	Set by the 11-fixing pattern	600mm across, 400mm along
Distance from panel edge	Min 100mm, max 200mm	Not stated	50mm to 150mm	Minimum 50mm
Minimum head diameter	Not stated	Smaller heads need higher frequency	35mm	Not stated
Fastener length or embedment	Fastener length equal to panel thickness	Not stated	Minimum 40mm penetration into the concrete	Minimum 25mm embedment for masonry screws
Named fastener	Hilti	Hilti X-IE6 / Ramset Insulfast GT3	Consult the fastener supplier	Insulation pins, shot-fired nails or masonry screws
Adhesive	Permitted, conditional	Only where penetration is impossible	Not a published method	Not mentioned

Read the fixing count against the board size, not on its own. GreenStuf Phenolic comes as a 1000 × 1200 board rather than a full 2400 × 1200, so its 5 to 6 fixings cover 1.20m² where everyone else's 11 cover 2.88m². By our arithmetic that is the densest schedule in the table, not the lightest.

Two products on one building is where this bites. Run a single schedule across both and one of them is outside its own instructions. We price each system to its own schedule and tell you if the specification has them mixed.

Source documents: GreenStuf ASL install instructions (Autex), Mammoth Carpark Panel safety and installation guidelines (InZone), Kingspan Kooltherm K10 G2 Masterspec section 4711KS (Comfortech), Kingspan Kooltherm K10 G2W installation guide (Comfortech), GreenStuf Phenolic Foam Board install instructions (Autex).

Can you glue-fix a carpark soffit?

Two questions get asked as one here. Adhesive instead of anchors is a narrow case and most manufacturers do not permit it. Adhesive alongside the anchors is standard, and it is how we install.

On a polyester liner we run a contact adhesive and laminate the panel to the slab. It grabs instantly and pulls the panel flat and tight to the concrete, with no sag and nothing moving while the crew is still on the lift. The anchors then go in to the manufacturer's schedule, and they are what carries the panel long term.

On Kingspan Kooltherm we swap to a concrete-grade construction adhesive that does not attack the phenolic core, applied in large dollops rather than laminated. Then the anchors, then every joint and cut edge taped. Kingspan warn that adhesives containing methyl ethyl ketone attack the core, which rules out one of the two contact adhesives most common on a New Zealand site, and getting that wrong shows up as a board gone soft behind the facing.

So you are not choosing between glue and fixings. You get both, and the fixing schedule is still the manufacturer's.

Adhesive on its own, with no anchors, is the narrow case. Straight from each install document:

GreenStuf ASL: Permitted in certain applications, with the adhesive and the substrate verified first.
Mammoth Carpark Panel: Only where structural steel in the concrete makes penetration impossible. Where it applies, two adhesives are required: full contact adhesive coverage, plus construction adhesive dobs carrying the long-term bond.
Kingspan Kooltherm K10 G2: No published adhesive method. Mechanical fixing or a proprietary grid.
GreenStuf Phenolic Foam Board: Adhesive is not mentioned in the install instructions.

What actually moves the price on your slab

Four things, and none of them is the panel.

1. What is already hanging there: A clear span runs at several times the rate of a level packed with sprinkler pipe, cable tray and lighting fixed hard to the soffit. The single biggest driver, and why we ask for the services drawings at quote stage.
2. The slab itself: Strength, age, and whether it is post-tensioned. Each of those changes which fastener is permitted and how many go in per square metre.
3. Panel thickness and product: Fastener length is set by the panel it passes through and the count is set by the manufacturer, so an R3.0 panel is a different fastener and a different rate from an R1.7.
4. Access: Scissor lift, mobile scaffold, or working around live traffic in stages. Machine time is programme time on a large deck.

Every job is different, so every quote states its inclusions and exclusions in full. We would rather have that conversation up front than in a variation later.

What our rate covers

We price the supply and install of the specified system as one line: material supply, consumables including adhesive, fixings and tapes as required, and labour. Every job is different, so every quote sets out its inclusions and exclusions in full. We fix to the manufacturer's published schedule, so the warranty you were sold is the warranty you end up with, and the QA records to prove it come with the handover.

Get your soffit priced

Tell us the specified system and the slab. Drawings can follow, and any conflict between the specification and the manufacturer fixing schedule comes back with the quote.

Fast turnarounds, within 24–48 hours
Fixing schedule confirmed against the specified product
Conflicts raised before you commit, not at PS3

Your project details are kept confidential.

Fixings: common questions

Can you glue carpark insulation to the soffit instead of fixing it?: We use adhesive on every job, but alongside the anchors rather than instead of them. On polyester it is a contact adhesive laminated to the slab so the panel pulls up flat; on Kingspan Kooltherm it is a construction adhesive that does not attack the phenolic core, in large dollops. Adhesive-only fixing is the narrow case: GreenStuf ASL permits it in certain applications, Mammoth only where steel in the concrete stops a penetration, and the two rigid boards publish no adhesive method at all.
How many anchors does each carpark soffit system need?: Eleven per 2400 by 1200 panel for GreenStuf ASL and Kingspan Kooltherm K10. Eleven to twelve for Mammoth. Five to six for GreenStuf Phenolic Foam Board. GreenStuf ASL sets maximum 600mm centres, 100 to 200mm from the panel edge. Kingspan asks for 50 to 150mm from the edge and a minimum 35mm head diameter. The schedules are not interchangeable.
Can you fix into a post-tensioned slab?: Yes, and it is routine work for us. The tendons are the constraint, not the concrete, so we scan and mark first and set the panel layout around what we find. Shot-firing blind is the thing to avoid, because a strand struck under load fails along its length. WorkSafe requires advice from the designer on fastener placement in post-tensioned structures, and a shot-fired anchor embeds 24 to 29mm at a depth you cannot adjust, so where cover is tight a drilled pin is the answer. Tell us at quote stage if any level is post-tensioned. It changes the method and the rate.
Does using a different fixing method void the insulation warranty?: Generally yes. All four make the warranty conditional on installation to the manufacturer's instructions, so a non-compliant install means the warranty never engages rather than being weakened. Kingspan is the most explicit: clause 12 of their April 2026 warranty statement rules out liability where the installation requirements have not been met.
How soon after the pour can you fix insulation to a slab?: Seven days is the working answer. Hilti's guidance is not to fire anchors into concrete poured on site until it has cured 7 days unless testing proves it will hold, and to base holding capacity on the strength on the day rather than the 28 day figure. A slab at ten days might be at 20 to 25 MPa where the drawing says 40, which is inside the window for some fasteners and under the floor for others. So we ask when the pour went down before we commit to a start date.

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Sources and external links(14)

Every figure on this page traces to one of the documents below. Where a manufacturer publishes conflicting versions, that is stated in the text rather than resolved silently.

Last updated 22 August 2026