Knauf Combi-Cut is a glass wool ceiling roll that arrives pre-perforated down its length. That means you separate it into the right width for your joist spacing by hand, with no tape measure and no knife. It sounds like a small thing. On a hot afternoon in a roof space, it is not.
This is the roll that keeps the job moving. Here is what makes it worth loading onto the trailer, whether you fit ceilings for a living, or you are doing your own home over a weekend. It also sits comfortably alongside the rest of the Summit ceiling and insulation range Swartland supplies.
Installation that keeps moving
The work goes quickest when the material does its share. Knauf Combi-Cut is a lightweight quilt, so it is easy to lift, carry and position. Because it splits along ready-made perforations, most of the fiddly cutting is gone before you even start. Less cutting means less loose fibre, less mess to sweep up, and less time spent crouched in the heat. From the roll coming off the vehicle to sitting snug between the joists, there are fewer steps in between.
What “Combi-Cut” actually means
Combi-Cut rolls are supplied partially perforated down their length. You pull the roll apart along the perforations to match your joist or truss centres, without measuring and without tools.
- For joists at 750mm centres, use one 800mm width or two 400mm widths.
- For joists at 600mm centres, split to suit that spacing the same way.
- Need a full-width top-up layer over the joists? Leave the roll unsplit and lay it at its full 1200mm width.
So one product covers the two spacings you meet most often in South African roofs, plus the top-up layer, without a single on-site width cut.
Why installers and DIYers choose it
1. Split to your spacing, no measuring
The factory perforations do the measuring for you. The roll drops neatly between the joists, so you don’t have to stop to mark widths or trim edges every few metres.
2. More cover per roll, fewer trips into the roof
Knauf Combi-Cut is compression packed, which fits more insulation into every pack. That saves space on the vehicle and in storage, and it means fewer rolls to haul up into the roof for the same ceiling. Fewer trips up the ladder, less handling, more ceilings done in a day.
3. Kinder to handle
Knauf glass wool is made with ECOSE Technology, a bio-based binder Knauf first introduced in 2008. It uses plant-based materials instead of the phenol and formaldehyde found in older binders, with no added formaldehyde and no artificial dyes or bleaches. That natural brown colour is the binder, not a coating. On site, it shows up in the way the roll feels to work with:
- Low itch
- Low dust as you lay it
- No strong chemical smell
It is also certified for indoor air quality (Eurofins Indoor Air Comfort Gold) and listed as Red List Free by Declare, which matters on a green-rated build, or if you simply want a healthier product sitting over your head.
4. It still performs where it counts
Easy to fit does not mean soft on performance:
- Non-combustible, with the top A1 Euroclass reaction-to-fire classification. It carries a SANS 53501-1 fire certificate and supports SANS 10400-T compliance, and the certificate is available on request.
- Made from up to 80% recycled glass.
- Rot-proof and non-hygroscopic, so it will not sustain vermin or encourage fungi, mould or bacteria.
If you are insulating more than the ceiling, Combi-Cut pairs well with Summit XPS boards, trap doors and cornices for cavity walls, under-floor applications and neat ceiling access, giving you one consistent insulation approach across the whole build.
Picking the right R-value
Combi-Cut ceiling rolls come in four R-value options, so you can match the roll to the spec:
- R1.25 (50mm)
- R1.85 (75mm)
- R2.5 (100mm)
- R3.38 (135mm)
The R-value tells you how well the roll resists heat flow. The higher the number, the more it slows heat moving through the ceiling, which keeps the space cooler through a summer afternoon and holds warmth in on a cold night. South Africa’s building energy rules (SANS 10400-XA) set minimum R-values for roof assemblies, and the figure you need depends on your climate zone, so check the spec or your local requirement before you order. Not sure which one fits? Contact our team and we can help you work it out.
Quick answers
Can I fit Knauf Combi-Cut without cutting it?
For width, usually yes. You separate it along the perforations to match your joist spacing by hand. You may still trim the odd end to length, but the lengthways width cuts are done for you.
What joist or truss spacing does it suit?
600mm and 750mm centres, the two most common in local roofs. At 750mm you use one 800mm strip or two 400mm strips.
Does glass wool still itch the way it used to?
Far less than the old stuff. The ECOSE binder means lower dust and lower itch, though it is still sensible to wear gloves, a dust mask and long sleeves in a roof space.
Is it safe in a fire?
Yes. It is non-combustible with an A1 Euroclass classification, the best reaction-to-fire rating there is, and it is backed by a SANS 53501-1 certificate.
Can a DIYer fit it?
Yes. It is light, it splits by hand and it needs no special tools, which makes it one of the more forgiving insulation jobs to take on yourself.
Get a quote
Need ceiling insulation that goes in quick and clean? Knauf Combi-Cut keeps the job simple from the first roll to the last. Request a quote on the widths and R-values your project needs, and we will sort you out with the right rolls for the ceiling. While you are planning, browse the full Swartland product ranges to see what else can lift the comfort and energy performance of the build.