Home / Applications / Geofoam Lightweight Civil Fill
Application

Geofoam Lightweight Civil Fill

Soft, compressible or low-bearing ground cannot carry the surcharge of a conventional soil or aggregate embankment without excessive settlement, lateral squeeze or bearing failure — and buried structures (basement roofs, culverts, services, retaining walls) cannot carry the earth pressure a full-weight fill imposes on them. Geofoam replaces that fill mass with engineered EPS block at roughly one to two percent of the weight of compacted soil, so the load applied to the subgrade or the structure is designed down rather than the ground being improved. It sits below the pavement or slab and above the subgrade or structure, entirely inside the civil works envelope — it is a load-management material first, and any thermal benefit is incidental.

Size this assembly Request a spec or quote
What it must achieve

Performance targets

Sustained design stress in the block
At or below the grade's compressive resistance @1% strain (the elastic / creep-control limit)
ASTM D7180 (geotechnical design) / ASTM D6817 (grades)
Never design to the @5% or @10% values — those are in the failure region and creep under permanent load. The per-grade @1% ladder is given in Key figures.
Total and differential settlement
Project-specific — set by the geotechnical engineer / roads authority, not by the material
Project specification, checked to ASTM D7180
The design action is choosing how much soil mass is replaced by EPS. Technopol publishes no settlement figure and none should be quoted.
Flotation / uplift
Buoyant uplift at the design groundwater or flood level must be exceeded by the permanent overburden (slab, pavement, cover soil) with the engineer's factor of safety
ASTM D7180
At 12–30 kg/m3 the blocks float. Uplift, not strength, usually governs where the water table can rise into the fill.
Hydrocarbon / solvent protection
Continuous impermeable geomembrane wherever a fuel, oil or solvent spill is credible (roads, fuel yards, workshops, oil-filled service trenches)
Detailing requirement to ASTM D7180 practice
Petrol, diesel and organic solvents dissolve EPS. This is a requirement, not an optional extra.
Fire performance in the permanent works
No fire-resistance (E/I/R, minutes) rating exists for geofoam — blocks must be permanently covered by slab, pavement or soil and kept clear of flues and hot works
SANS 53501-1 gives reaction-to-fire only; it is NOT a fire-resistance rating
All EPS is combustible (fire-retardant grades are treated, not non-combustible). Exact tested scope of the only current reaction-to-fire report is in Key figures.
Thermal contribution
Incidental only — no R-value or U-value per thickness is published for geofoam
n/a
Where thermal performance is the objective (under-slab insulation, SANS 10400-XA compliance), specify a board product with a declared lambda and thickness, not geofoam.
The geofoam fill build-up, layer by layer
The same build-up, in the order it goes together. Generated from the assembly data this page lists below, so the drawing and the words cannot disagree.
t">
Where it goes

The assembly

Section through the geofoam fill assembly
  1. Pavement, surfacing or floor slab
  2. Base / sub-base course
  3. Load-distribution slab…
  4. Separation and protection layer…
  5. Technopol geofoam EPS blocks — laid dry, no compaction
  6. Levelling / bedding layer on the prepared subgrade
  7. Prepared subgrade and drainage

Layers listed outside → inside. The section is drawn to show the ORDER of the layers and where the Technopol product sits in it; the band widths are not to scale.

What each layer is doing — 7 layers, full detail
  1. Pavement, surfacing or floor slab — The trafficked or loaded surface. Hot-applied bitumen must never be placed directly against the EPS — it goes on the base course above the load-distribution slab.
  2. Base / sub-base course — Conventional granular layerworks, thickness per the pavement design.
  3. Load-distribution slab (typically reinforced concrete) or geogrid-reinforced layer — Spreads wheel and point loads so the sustained stress reaching the block stays at or below its compressive resistance @1% strain.
  4. Separation and protection layer — geomembrane and/or geotextile — Impermeable geomembrane where a hydrocarbon or solvent spill is credible; geotextile to keep fines and bedding sand out of the block joints.
  5. Technopol geofoam EPS blocks — laid dry, no compaction — Staggered courses with cross-joints broken between layers, field-cut to line and level, mechanically inter-connected (barbed connector plates). Grade chosen from the EPS12–EPS30 ladder against the sustained design stress.
  6. Levelling / bedding layer on the prepared subgrade — Thin screeded sand or fine-graded layer. Geofoam is a rigid block — it will not conform to a rutted platform, and unsupported blocks crack.
  7. Prepared subgrade and drainage — Blocks kept above the design groundwater level with positive drainage so water cannot pond in or under the fill and generate uplift.
Which products, and why

The products that do this job

Product

Geofoam Lightweight Fill

The engineered lightweight fill itself — moulded closed-cell EPS block across the EPS12–EPS30 grade ladder, field-cut and placed dry without compaction.

View product →

Product

Technoblock Slab Blocks & Void Formers

Raw large-format EPS block supply from the same moulding line — the stock from which geofoam blocks and bespoke cut shapes are produced. Cut EPS void formers used alongside the fill to form permanent voids, tapers and stepped transitions in the concrete works (slab soffits, abutment ledges) where full-block geofoam is the wrong shape.

View product →

Product

2D Shapes & Sheets

Hot-wire cutting of blocks to bespoke profiles — tapered transition wedges, battered abutment faces, service cut-outs — to a factory cutting schedule.

View product →

The numbers

Performance data

Every test report and certificate behind these figures is held by Technopol and is available on request.

12 figures, full data
PropertyValueStandard
Density (grade span, EPS12–EPS30)12–30 kg/m3ASTM D6817
Compressive resistance @1% strain — the design load limit15–100 kPaASTM D7180
Compressive resistance @1% strain, per grade (EPS12 / 15 / 20 / 24 / 30)15 / 17 / 45 / 70 / 100 kPaASTM D7180
Compressive strength @10% strain — failure-region strength, NOT a design load60–200 kPaASTM D6817
Self-weight relative to compacted soil fill~1–2% (12–30 kg/m3 against ~1 800–2 000 kg/m3 typical compacted fill) ration/a — derived
Thermal conductivity (lambda) @10 degC — incidental; no R/U per thickness published0.033–0.045 W/m.KDatasheet value
Water absorption (long-term immersion)< 4 %Datasheet figure
Typical block size (other sizes cut to order)2550 x 1250 x 960 mmn/a
Reaction to fire — FR (flame-retardant) EPS; tested scope is a 60 mm EPS FRCel 20DV sheet, NOT the buried geofoam block gradesB-s1,d0 classSANS 53501-1 (Euroclass) — reaction to fire, not fire resistance
Fire-resistance rating (E/I/R minutes) for geofoamNone — geofoam carries no fire-resistance rating; all EPS is combustible and must be permanently covered in the works n/aSANS 10177-2
Governing standards — no SANS geofoam standard and no Agrement SA certificate for geofoam existsASTM D6817 (physical properties) / ASTM D7180 (geotechnical design) / ASTM D7557 (sampling) n/aASTM D6817 / D7180 / D7557
Manufacturing quality system (company credential, not a product approval)ISO 9001:2015 — scope includes EPS Blocks and EPS Sheets n/aISO 9001:2015 (EQCSA, SANAS C22)
Size it

EPS Lightweight Fill Design Checker (geofoam)

Enter the pavement/slab build-up, surcharge and groundwater level: the checker returns the sustained stress arriving at the top of the block, the grade whose compressive resistance @1% strain covers it, and the uplift/flotation check. The grade properties in the tool are the datasheet ladder — the project design must be signed off by the geotechnical engineer.

Open the tool → Write the spec clause

On site

Installation

The full installation sequence — 12 steps
  1. Confirm the design before ordering: the sustained stress at the top of the block (after the load-distribution slab spreads it), the grade whose compressive resistance @1% strain exceeds it, and the flotation check against the design groundwater/flood level. Do not select a grade from the @10% strength values.
  2. Prepare and trim the subgrade or structure top to a plane surface and screed a thin bedding layer. Geofoam is rigid — it will not conform to a rutted platform, and unsupported blocks crack.
  3. Provide positive drainage under and around the fill so water cannot pond within it; keep the block base above the design groundwater level wherever possible.
  4. Lay the separation and protection layer: geotextile against the subgrade, plus a continuous impermeable geomembrane wherever a fuel, oil or solvent spill is credible.
  5. Place the blocks dry in staggered courses with cross-joints broken between successive layers. No compaction, no wetting, no plate-vibration on the EPS.
  6. Mechanically inter-connect the courses (barbed connector plates) so construction traffic and hydraulic loading cannot displace the blocks before cover is on.
  7. Field-cut with hot-wire or fine-tooth saw for edges, tapers and service penetrations. Pack gaps with cut EPS — never with soil, which reintroduces the mass the design removed.
  8. Ballast promptly. Placed blocks are light enough to be blown around or floated in a rainstorm — do not leave a course exposed and unrestrained overnight.
  9. Cast or place the load-distribution slab / reinforced layer before any plant, base course or surfacing load is applied. Never run plant directly on bare geofoam.
  10. Keep hot works, bitumen kettles, open flame and flue penetrations away from exposed EPS during construction; hot-applied bitumen goes on the base course above the slab, not on the blocks.
  11. Cover or sheet stockpiled and placed block that will not be buried promptly — EPS degrades under UV.
  12. Keep the finished fill permanently covered by slab, pavement or soil. Geofoam has no fire-resistance rating and is not intended to remain exposed in the permanent works.
The limits

Where not to use this

A material specified for the wrong job fails you, then us.

Where fuel, oil, solvent or hot bitumen can reach the blocks and no impermeable membrane is provided (fuel forecourts, workshops, hydrocarbon-contaminated ground, oil-filled cable trenches)
EPS is dissolved by hydrocarbons and organic solvents. Contact destroys the block and the lost volume appears as sudden local settlement — there is no slow warning.
→ Designed geomembrane encapsulation for the spill case, or a mineral lightweight fill (foamed concrete, expanded clay aggregate) where the exposure cannot be reliably excluded.
Below the design groundwater or flood level, or anywhere the fill can be submerged, without ballast designed for uplift
At 12–30 kg/m3 the blocks float; buoyancy, not strength, governs. A fill that is safe under wheel loads can be lifted bodily by a rising water table. Prolonged immersion also lets EPS take up moisture, adding weight and degrading the (already incidental) thermal value — the same mechanism that makes plain EPS a poor choice in an inverted/protected-membrane roof.
→ Raise the fill above the water table, design permanent overburden ballast, or use a heavier lightweight fill (foamed concrete) below water.
Where the sustained design stress would exceed the grade's compressive resistance @1% strain — including anyone sizing off the @5%/@10% numbers
Beyond about 1% strain EPS creeps under permanent load. The @10% values (60–200 kPa) are failure-region strengths, not working loads; designing to them produces a fill that keeps settling for the life of the structure.
→ Move up the grade ladder (EPS24/EPS30), thicken the load-distribution slab to spread the stress, or use structural lightweight concrete where the load cannot be spread far enough.
As permanently exposed fill, or under a surface that will be left open — no slab, pavement or soil cover
EPS is combustible (fire-retardant grades are treated, not non-combustible), UV-degradable and mechanically soft. Geofoam has NO fire-resistance (E/I/R) rating; the only current reaction-to-fire result on file (B-s1,d0, IT 23-08-00009) was established on a 60 mm FRCel 20DV sheet and is not extended to the buried block grades — and a reaction-to-fire class is not a fire-resistance rating in any case.
→ Design a permanent slab/pavement/soil cover as part of the works, or use a non-combustible mineral fill where cover cannot be guaranteed.
In direct contact with heat — hot-applied bitumen poured onto the blocks, steam or hot-process pipework, boiler and flue penetrations, hot works during construction
EPS softens and melts well below the temperature of hot-applied bitumen and hot service lines; the melted zone becomes a void and the fill loses support locally.
→ Interpose the load-distribution slab and base course before any hot-applied surfacing; sleeve or box hot services in a mineral material (stone wool, concrete).
As the answer to a thermal requirement — claiming geofoam toward a SANS 10400-XA roof/ceiling total R-value (3.7 m2K/W in all zones under XA:2021; Zone 5 humid-coastal retains 2.7 with roof ventilation) or a wall requirement
Geofoam is supplied as a load-bearing fill grade rather than a wall-insulation board, and its lambda is a grade-span datasheet figure — use the cavity or continuous-insulation boards where a wall R-value has to be met. Separately, most masonry walls need nothing added at all — double-skin cavity masonry and plastered single leaf >=140 mm are deemed-to-satisfy under XA (only lightweight / non-qualifying walls need a minimum total R >= 0.35 m2K/W). External walls with a SURFACE DENSITY LIGHTER THAN 270 kg/m2 (light steel frame, timber frame, drywall, sandwich panel) must reach a minimum TOTAL R-value of 2.2 m2K/W in energy zones 1, 2, 6 and 7, and 1.9 m2K/W in zones 3, 4, 5 and 5H (SANS 10400-XA:2021, ch.3). And any walling with metal sheet, metal studs, metal tracks or metal battens fixed to each other SHALL have a thermal break. The 0.35 m2K/W figure applies to MASONRY types not covered by the standard provisions - it is NOT the lightweight-wall bar.
→ Use a board product with a declared lambda and thickness for under-slab or envelope insulation and confirm the requirement in the free SANS 10400-XA compliance checker (../../technical/xa-compliance/).
Where the specification demands an Agrement SA certificate for the fill
Agrement SA 2020/609 covers the LiteCore Building System only, as a non-load-bearing wall. There is no Agrement certificate for geofoam, and another system's product certificate must never be offered as cover for this one.
→ Specify to ASTM D6817 / D7180 / D7557 with a project-specific geotechnical design, plus batch verification of the delivered grade where the client requires it.
Where it has been used

Project references

Technoblock Slab Blocks & Void Formers

156 Wright Road

Commercial

2D Shapes & Sheets

Riverstone Mall, Meyerton

Meyerton · Retail

Geofoam Lightweight Fill

Sun International Times Square

Menlyn, Pretoria · Casino / hotel

Geofoam Lightweight Fill

South African Reserve Bank (SARB)

Institutional / banking

Geofoam Lightweight Fill

Liberty Life Style Centre

Commercial

Geofoam Lightweight Fill

Lesotho Highlands Water Project, Phase II

Lesotho · Civil / water infrastructure

All 54 project references →

Questions

Specifier FAQ

Does geofoam need compaction?
No. It is placed dry as rigid blocks in staggered, mechanically inter-connected courses — no compaction, no moisture conditioning, no layer-by-layer density testing. That is exactly why it is used where a compacted fill would surcharge soft ground or a buried structure.
How do I choose the grade?
Work out the sustained stress arriving at the top of the block once the load-distribution slab has spread it, then pick the grade whose compressive resistance @1% strain exceeds it. The @1% ladder is 15 / 17 / 45 / 70 / 100 kPa for EPS12 / 15 / 20 / 24 / 30. Never size against the @10% strengths (60–200 kPa) — those are failure-region values and designing to them causes long-term creep.
Will it float?
Yes, if you let it. At 12–30 kg/m3 the fill is far lighter than water, so uplift is often the governing check. Keep the base above the design groundwater level, drain the surrounds, and confirm the permanent overburden exceeds the buoyant force at the design flood level with the engineer's factor of safety. The geofoam design checker runs this check alongside the stress check.
Can trucks and plant drive on it?
Not on the bare blocks. Traffic loads must be spread by the load-distribution slab and base course above; plant running on exposed EPS crushes and gouges it. Place the cover before any construction traffic.
What happens if diesel or petrol reaches it?
It dissolves the EPS. Wherever a hydrocarbon or solvent spill is credible a continuous impermeable geomembrane must be designed into the build-up — a requirement, not a precaution. If the exposure cannot be reliably excluded, use a mineral lightweight fill instead.
What is the fire rating?
There is no fire-resistance (E/I/R, minutes) rating for geofoam and none should be quoted. The only current reaction-to-fire result on file is Class B-s1,d0 to SANS 53501-1 (report IT 23-08-00009, Ignis Testing, valid to ~2028), established on a 60 mm FR-grade EPS FRCel 20DV sheet — that is a reaction-to-fire classification, not a fire-resistance rating, and it is not formally extended to the buried geofoam grades. All EPS is combustible (fire-retardant grades are treated, not non-combustible), so the permanent works must keep it covered by slab, pavement or soil and clear of flues and hot works.
Is geofoam Agrement certified?
No. Agrement SA certificate 2020/609 covers the LiteCore Building System only (as a non-load-bearing wall) and does not extend to geofoam or any other Technopol product. Geofoam is specified against ASTM D6817 / D7180 / D7557 with a project-specific geotechnical design. Technopol's ISO 9001:2015 certification (scope includes EPS blocks and sheets) is a manufacturing quality-system credential — not a product performance approval.
Does the fill also insulate the ground below it?
Incidentally. The datasheet lambda span is 0.033–0.045 W/m.K, but no R-value or U-value per thickness is published for geofoam and none may be claimed toward SANS 10400-XA. If insulation is the objective rather than a by-product, specify a board product with a declared lambda and check the requirement in the XA compliance checker (../../technical/xa-compliance/).
How is it cut and detailed on site?
Blocks are field-cut with hot-wire or fine-tooth saws for edges, tapers and service penetrations; complex profiles (battered abutment faces, transition wedges) are better hot-wire cut in the factory to a cutting schedule. Gaps between blocks are packed with cut EPS, never with soil — soil in the joints reintroduces the very mass the design removed.
How long does it last?
Buried, drained, protected from hydrocarbons and loaded within its @1% limit, EPS block fill is chemically stable and does not rot or decompose. The durability risks are all detailing risks: solvent contact, submergence, over-stress creep, UV and heat on exposed block. Every one of them is designed out in the build-up above.

Ready to specify?

Send us the drawings. We will size it, detail it and quote it.

Request a spec or quote

Technical resource

Who should we send this to?

We release technical documentation to named engineers and specifiers so we can support you properly on the project. One entry unlocks everything.

We will email you this document, and we may follow up about it. We will not add you to anything else unless you tick the box. We do not share or sell your details. How we handle your information.