FIBRE X Screed fibre
Alkali-resistant fibreglass reinforcement fibre for screeds and mortars
Alkali-resistant glass fibre that controls shrinkage cracking through the full depth of a screed.
FIBRE X sizes and key figures
Dry fibre you add at batching to cementitious screeds, mortars, renders and toppings. It is not structural reinforcement and never replaces steel where an engineer specifies it.
- Standard dose
- 1 kg / tonneof dry mix; 20 g per 20 kg bag · TDS p3
- Enhanced dose
- 1.5–2.0 kg/tof dry mix; 30–40 g per 20 kg SCREED X bag · TDS p4
- Per m³
- ≈ 2 kgof screed mix at the standard dose · TDS p3
- Pack
- 1 kgdry, sealed packaging · TDS p3
- Dry blend
- 60 sbefore water, then mix 30–60 s longer · TDS p4
- Apply at
- 5–35°Chost mix temperature range · TDS p3
- Density
- ≈ 2.6 g/cm³typicalfibre density · TDS p3
- Shelf life
- 36 monthsdry, sealed packaging · TDS p3
- Effect on timing
- No changedrying, curing and traffic times follow the host mix · TDS p3
From the FORSPEC data sheet, TDS-FIBREX · Revision 1 · 25 August 2026. Times are at 25°C and 50% relative humidity unless the data sheet says otherwise. Typical = FORSPEC’s own typical value, not a laboratory-certified one.
Where FIBRE X is used
Use it for
- FORSPEC SCREED X and FORCEM SCREED BINDER screeds
- Bonded, unbonded and floating screeds
- Screeds over underfloor heating and over FORSPEC membranes
- Roofing screeds and falls screeds
- Screed repair mortars, renders and concrete toppings
- Reduced-thickness screeds in the enhanced mix, with written approval
Know before you start
- Not structural reinforcement: never replaces steel where an engineer specifies it
- Does not replace movement, control or expansion joints
- Does not allow thinner screeds alone: needs ACTFLEX 300 and written FORSPEC approval
- Do not add to a wet mix or exceed the enhanced dose
Its FORSPEC systems
How to apply FIBRE X
- 01
Measure
Weigh the dose: 1 kg per tonne of dry mix (20 g per 20 kg), or 1.5–2.0 kg per tonne for enhanced crack control. Use a scale or pre-weighed sachet, not by eye.
- 02
Charge
Add sand, binder and aggregates to the mixer, then the FIBRE X. Add it dry. Fibre added to a wet mix balls up and clumps.
- 03
Dry blend
Dry blend for about 60 seconds so the fibre spreads evenly before any water goes in.
- 04
Add water
Add water and any approved additives gradually. Mix until uniform, 30–60 seconds longer than a normal mix.
- 05
Check
Take a sample of the wet mix and confirm the fibres are evenly spread with no clumps or balls. If clumped, mix longer and review the batching order.
- 06
Place
Place and compact as normal. Keep every movement, control and expansion joint through the screed at full depth.
A short guide from the data sheet. Read the full FIBRE X TDS before you start.
Drawings for the systems it goes in
FORSPEC standard details as PDF and DXF. Each sheet is a generic detail: the specification names the products.
FIBRE X questions
How much FIBRE X do I add?
Standard crack control is 1 kg per tonne of dry mix, or 20 g per 20 kg bag. Enhanced is 1.5 to 2.0 kg per tonne, or 30 to 40 g per 20 kg SCREED X bag. About 2 kg per m³ of screed at the standard dose.
Does FIBRE X replace steel mesh?
No. It is not structural reinforcement and must never be substituted for engineered reinforcement. It controls plastic shrinkage cracking as the mix gains strength.
When do I add FIBRE X to the mix?
Dry, before any water. Add it with the sand and binder, dry blend for about 60 seconds, then add water. Adding it to a wet mix causes balling and uneven dispersion.
Can FIBRE X let me make a thinner screed?
Not on its own. Reduced-thickness screeds need the full enhanced mix, with ACTFLEX 300, the enhanced dose and written FORSPEC approval. Verbal approval is not enough.
Does it change drying or traffic times?
No. Drying, curing, foot traffic and covering times are set by the host mix. See the FORSPEC SCREED X or FORCEM SCREED BINDER TDS.
Does FIBRE X replace movement joints?
No. All movement, control and expansion joints must still be provided in full, and existing joints must be carried through the screed.
Used with FIBRE X
FIBRE X data sheet
Always work from the current data sheet. Every FORSPEC TDS and SDS →
Specify it. Or buy it.
Send the drawings or photos and FORSPEC comes back with the system, the details and the quantities. Or find a FORSPEC stockist for FIBRE X.