TryBuildCalcPlinth Filling / Floor Base Calculator (Soil/Sand Fill, PCC Bed & DPM)
Calculate compacted soil/sand fill, PCC bed, and DPM quantity for a plinth or floor base.
🕒 Last updated: July 30, 2026
Plinth Footprint
ℹ️Internal footprint length to be filled, from the foundation/plinth drawing.
ℹ️Internal footprint width to be filled.
ℹ️Set to more than 1 if several identical rooms/blocks share this same footprint and fill depth.
Fill Layer
ℹ️Height from formation level to the underside of the PCC bed; commonly 150-450 mm for residential plinths.
ℹ️Extra loose volume needed over the compacted volume — pre-filled per material, adjust if your supplier's data differs.
PCC Bed
ℹ️Commonly 50-100 mm for a residential floor base.
DPM (Damp-Proof Membrane)
Cost
For a 80.00 m² (861 sqft) plinth footprint filled 200 mm deep with soil / select fill, you need approximately 33.81 tonnes of fill material and 6.300 m³ (222.5 cft) of PCC bed concrete.
Compacted Fill
Material: Soil / Select Fill
Compacted volume: 16.000 m³ (565.0 cft)
Loose volume (before wastage): 18.400 m³ (649.8 cft)
Loose volume (with wastage): 19.320 m³ (682.3 cft)
Material to order: 33.81 tonnes
PCC Bed (1:4:8)
Thickness: 75 mm
Total concrete: 6.300 m³ (222.48 cft)
Cement: 21.5 bags
Sand: 2.985 m³ (105.4 cft)
Aggregate: 5.970 m³ (210.8 cft)
DPM (Damp-Proof Membrane)
DPM not included in this estimate.
Assumptions Used
Fill: loose volume = compacted volume × (1 + compaction%), then wastage on top | PCC: dry volume factor 1.54, wastage applied to cement/sand/aggregate together | DPM: rolls = ceil(area × (1 + wastage%) ÷ (roll area × (1 − overlap%))) | Flooring/screed/tiling above the DPM is outside this calculator's scope — see Limitations.
Approximate results for planning only. Verify with a professional.
Unsure where the DPM should sit relative to the PCC bed? Plinth Filling Guide →
Plinth Filling Cross-Section
What Is a Plinth Filling / Floor Base Calculator?
Plinth filling is the earthwork that raises the ground level inside a building's foundation walls up to the underside of the floor slab — the gap left over once footings and the plinth beam are cast. This calculator estimates everything needed to fill and prepare that base in one pass: compacted fill (soil, murram, sand, or hardcore/crushed aggregate), a PCC (plain cement concrete) bed on top of the fill, and a DPM (damp-proof membrane) laid over the PCC bed before the floor slab is poured.
It's built as a companion to this site's Backfill, PCC, and Waterproofing calculators — use this one when you want the fill-to-DPM sequence combined into a single result, instead of running three separate calculators and adding the numbers up by hand.
What makes this calculator different:
Most tools online estimate a sub-base, a PCC bed, or a DPM in isolation. This calculator combines all three layers of a real plinth-filling sequence into one estimate, using the same compaction, dry-volume, and sheet-coverage math as this site's dedicated Backfill, PCC, and Waterproofing calculators.
Applicable standards / regional terms:
- India: plinth filling with soil/murram, IS 1200 (method of measurement) conventions for earthwork and PCC.
- UK: the equivalent build-up is described as hardcore/sub-base plus DPM under Building Regulations Approved Document C, with DPM commonly specified to BS 8102.
- US: granular fill under a slab-on-grade, with vapor retarders specified per ASTM E1745 and compaction per ASTM D1557 (Modified Proctor).
How Is Plinth Filling Calculated?
The calculation happens in three parts — compacted fill, PCC bed, and DPM — then an optional cost estimate on top.
Step 1 — Footprint Area
Area = Length × Width
Total Area = Area × Number of Identical Sections
If sections differ in size: Total Area = Sum of (Length × Width × Count) for every section
The footprint is the internal area to be filled, taken from the foundation/plinth drawing. Number of Identical Sections multiplies the whole result for repeated rooms/blocks of the same size; for rooms of different sizes, switch on "Multiple Different-Sized Sections" and the calculator sums every row's area into one combined total automatically.
Step 2 — Compacted Fill
Compacted Volume = Total Area × Fill Depth
Loose Volume = Compacted Volume × (1 + Compaction %)
Loose Volume (with wastage) = Loose Volume × (1 + Wastage %)
Order Quantity (tonnes) = Loose Volume (with wastage) × Material Density ÷ 1000
Delivered fill material is loose and has more air voids than it will once compacted in place, so the compaction percentage inflates the compacted (finished) volume into the loose volume you actually need to order; wastage is then applied on top of that loose volume, and the resulting figure converts directly to a tonnage using the material's density — the same convention this site's Backfill and Aggregate Coverage calculators use. For "Custom Fill Material", the density you enter is used directly in this step instead of a preset figure.
Step 3 — PCC Bed
Wet Volume = Total Footprint Area × PCC Thickness
Dry Volume = Wet Volume × 1.54
Cement / Sand / Aggregate = Dry Volume split by mix ratio parts
Wastage % applied to cement bags, sand, and aggregate together
This uses the same footprint area as Step 1 (so it stays correct whether you're using a single footprint or several differently-sized sections) and the same PCC formula as this site's dedicated PCC Calculator — a thin, lean-mix concrete bed that gives a firm, level surface for the DPM and floor slab above, not a structural element in its own right.
Step 4 — DPM (Damp-Proof Membrane)
Final Area = Total Area × (1 + Wastage %)
Roll Coverage = Roll Length × Roll Width × (1 − Overlap %)
Rolls Needed = ROUND UP(Final Area ÷ Roll Coverage)
Wastage accounts for the edge upturn and offcuts, while the overlap percentage accounts for the minimum lap required at every joint between adjoining sheets so ground moisture can't find a path through.
Step 5 — Add Contingency (Optional)
Base Cost = Fill Cost + PCC Cost + DPM Cost
Contingency Amount = Base Cost × (Contingency % ÷ 100)
Total Cost = Base Cost + Contingency Amount
Contingency is an optional buffer on top of the combined base cost to cover unexpected variance — supplier rate changes, delivery charges, or material substitution. It defaults to 0%; a commonly used range is 5-15%.
Worked Example
This example walks through your current inputs above, using the same steps as the Formula section. Each table shows the calculation, the values substituted in, and the result it produces.
Input Values Used
| Input | Value | Why it is used |
|---|---|---|
| Plinth footprint | 10 m × 8 m, 1 section(s) | Sets the area every layer's volume is built on |
| Fill material / depth | Soil / Select Fill, 200 mm | Sets fill density and compacted volume |
| Compaction / wastage | 15% compaction, 5% wastage | Converts compacted volume into the loose quantity to order |
| PCC bed | 75 mm, 1:4:8, 5% wastage | Sets PCC wet volume and cement/sand/aggregate split |
Step 1 — Footprint Area
The footprint area is the base every layer above is built on — fill volume, PCC volume, and DPM area all scale directly from it.
| Calculation | Substitution | Result |
|---|---|---|
| Area | 10 m × 8 m | 80.000 m² |
| Total area | 80.00 × 1 | 80.000 m² (861.11 sqft) |
Step 2 — Compacted Fill
The compacted volume is what the finished, settled fill will occupy. Compaction inflates that into the loose volume, wastage inflates it once more into the loose volume actually ordered, and that final volume converts directly into a tonnage using the material's density — the same figure the cost step below uses.
| Calculation | Substitution | Result |
|---|---|---|
| Compacted volume | 80.00 m² × 200mm | 16.000 m³ |
| Loose volume | 16.000 m³ × 1.15 | 18.400 m³ |
| Loose volume (with wastage) | 18.400 m³ × 1.05 | 19.320 m³ (682.3 cft) |
| Order quantity | 19.320 m³ × 1750 kg/m³ ÷ 1000 | 33.81 tonnes |
Step 3 — PCC Bed
The PCC bed volume comes from the same total footprint area as Step 1, not the fill's compacted volume — it's a separate, thin layer cast on top of the finished fill.
| Calculation | Substitution | Result |
|---|---|---|
| Wet volume | 80.00 m² × 75mm | 6.000 m³ |
| With 5% wastage | 6.000 × 1.05 | 6.300 m³ (222.5 cft, 21.5 bags) |
Step 5 — Cost & Contingency
| Calculation | Substitution | Result |
|---|---|---|
| Enable cost estimation above to see fill, PCC, and DPM cost | — | |
Therefore, this 80.0 m² plinth needs approximately 33.81 tonnes of fill material, 6.300 m³ of PCC bed concrete.
Essential Checklist+−
Complete these critical checks before approving the work or proceeding to the next construction stage.
✓Footprint & Formation Verification+-
- Plinth footprint length and width used match the architectural/foundation drawing, not assumed round numbers.
- Formation level (base of fill) is cleared of organic matter, debris, and standing water before fill placement begins.
- Foundation trenches and plinth beam are fully cured and backfilled at the sides before internal plinth filling starts, so the fill has lateral support.
✓Fill Material & Compaction+-
- Fill material matches what's specified/available on site (soil, murram, sand, or hardcore), not just whichever default was left selected.
- Fill is placed and compacted in thin layers (commonly 150-250 mm loose per lift), not dumped and compacted in one thick layer.
- Fill material is free of large debris, construction waste, or oversized boulders that would leave voids under the PCC bed.
✓PCC Bed+-
- PCC mix ratio and thickness match the project specification.
- PCC is placed only after the fill below has been tested/confirmed as adequately compacted, not poured on a freshly dumped, unconsolidated layer.
✓DPM Installation+-
- DPM gauge/thickness meets the project specification (commonly 300 micron / 1200 gauge minimum).
- Sheets are lapped by at least the specified minimum (commonly 150mm) at every joint, and joints are sealed.
- DPM turns up at the perimeter walls to link with the wall damp-proof course, not left flat and stopping short at the wall face.
✓Final Check+-
- No settlement, soft spots, or hollow sound is detected when walking the compacted fill surface before the PCC bed is poured over it.
- Fill rate unit (per m³ vs per tonne) and PCC rate unit (per m³ vs per cft) match what the supplier actually quoted — mixing units silently changes the cost estimate.
Full QC Checklist+−
Verification checklist for plinth filling — covering footprint/formation, fill material and compaction, PCC bed, DPM installation, and final check. Use the Essential Checklist for critical checks; expand to Full QC Checklist for complete quality assurance.
✓Footprint & Formation Verification+-
- Plinth footprint length and width used match the architectural/foundation drawing, not assumed round numbers.
- Formation level (base of fill) is cleared of organic matter, debris, and standing water before fill placement begins.
- Fill depth used matches the actual difference between formation level and the underside of the planned PCC bed.
- Foundation trenches and plinth beam are fully cured and backfilled at the sides before internal plinth filling starts, so the fill has lateral support.
- Termite/soil poison treatment is applied to the formation level before fill placement, where specified, since it can't be added once fill covers it.
✓Fill Material & Compaction+-
- Fill material matches what's specified/available on site (soil, murram, sand, or hardcore), not just whichever default was left selected.
- Fill is placed and compacted in thin layers (commonly 150-250 mm loose per lift), not dumped and compacted in one thick layer.
- Each layer is compacted to a firm, non-yielding surface (tested by walking over it or with a plate compactor pass) before the next layer is placed.
- Fill is watered to near-optimum moisture content before compaction, since both bone-dry and waterlogged fill compact poorly.
- Fill material is free of large debris, construction waste, or oversized boulders that would leave voids under the PCC bed.
- Compaction near the plinth beam and column stubs is done with hand tampers, not heavy plate compactors, to avoid damaging or displacing them.
✓PCC Bed+-
- PCC mix ratio and thickness match the project specification.
- PCC surface is level and reasonably smooth, since the DPM needs to lie on it without sharp projections that could puncture it.
- PCC is placed only after the fill below has been tested/confirmed as adequately compacted, not poured on a freshly dumped, unconsolidated layer.
- PCC bed is cured for the applicable minimum period before the DPM and floor slab load is placed on it.
✓DPM Installation+-
- DPM gauge/thickness meets the project specification (commonly 300 micron / 1200 gauge minimum).
- Sheets are lapped by at least the specified minimum (commonly 150mm) at every joint, and joints are sealed.
- DPM is free of tears or punctures before the floor slab/screed is poured over it.
- DPM turns up at the perimeter walls to link with the wall damp-proof course, not left flat and stopping short at the wall face.
- DPM is protected from damage by reinforcement fixing, foot traffic, or material stacking between installation and the floor slab pour.
✓Final Check+-
- Finished floor level (after slab/screed/flooring) lines up correctly with the plinth beam, door thresholds, and external ground level.
- Total fill, PCC, and DPM material used is reconciled against this calculator's estimate before closing out the item in records.
- No settlement, soft spots, or hollow sound is detected when walking the compacted fill surface before the PCC bed is poured over it.
- Site is photographed at each stage (compacted fill, PCC bed, DPM laid) before it's covered by the next layer, for future reference.
- Fill rate unit (per m³ vs per tonne) and PCC rate unit (per m³ vs per cft) match what the supplier actually quoted — mixing units silently changes the cost estimate.
- Contingency percentage (if used) reflects how well the fill, PCC, and DPM rates are actually known — not left at a default 0% for a genuinely unconfirmed quotation.
Reference Tables
Typical fill lift thickness by compaction method
| Region / Convention | Loose Lift Thickness | Notes |
|---|---|---|
| Hand rammer (India/general) | 150-250 mm | Ramming with 7-10 kg rammers |
| Mechanical plate compactor | up to 300 mm | Higher compaction energy per pass |
| UK hardcore practice | ~75 mm per lift | Compact each lift before adding the next |
| US structural fill (ASTM D1557) | up to 300 mm (12 in) | Compacted to ~95% relative compaction |
Fill material default density & compaction
| Material | Density | Default Compaction Allowance |
|---|---|---|
| Soil / Select Fill | 1750 kg/m³ | 15% |
| Murram / Laterite Fill | 1750 kg/m³ | 15% |
| Sand Fill | 1600 kg/m³ | 10% |
| Hardcore / Crushed Aggregate (MOT Type 1 / GSB) | 1900 kg/m³ | 20% |
PCC bed thickness by common use
| Use | Commonly Cited Thickness | Typical Mix |
|---|---|---|
| Residential floor base | 50-75 mm | 1:4:8 or 1:5:10 |
| Footing/foundation blinding | 75-100 mm | 1:3:6 or 1:4:8 |
| Industrial/heavier floor base | 100-150 mm | 1:3:6 or richer |
DPM gauge/thickness by region
| Region / Standard | Minimum Spec |
|---|---|
| UK (BS 8102, domestic ground floors) | 300 micron (1200 gauge) polythene |
| US (ASTM E1745) | Class A/B/C vapor retarder rating, selected by moisture risk |
| India (common site practice) | 250-300 micron (1000-1200 gauge) polythene |
These are commonly referenced conventions, not a universal standard — always confirm fill depth, PCC mix, and DPM specification against your project's applicable building code before finalizing.
Usage Guide
- Use during early estimation to plan fill material, PCC, and DPM procurement for a plinth or floor base before work begins.
- Enter the actual formation-to-underside-of-PCC depth from the site levels, not a rounded assumption.
- Use "Multiple Different-Sized Sections" for a building where rooms share the same fill depth and PCC spec but have different footprints; run the calculator again separately only if fill depth itself genuinely varies by room.
- Cross-check the fill depth against the plinth beam and door threshold levels so the finished floor lines up correctly.
- Download the checklist PDF alongside the estimate for a site-ready verification record.
Practical Plinth Filling Tips
- Clear organic matter, debris, and standing water from the formation level before placing any fill — a soft or wet base will settle unevenly later.
- Place and compact fill in thin layers rather than one thick dump — compaction effort can't reach uniform density much beyond about 250-300 mm per pass.
- Water each layer lightly before compacting if the material is very dry — proper moisture content noticeably improves compaction, especially for soil/murram.
- Keep the PCC bed surface smooth and free of sharp projections before laying the DPM — a puncture defeats the whole point of the membrane.
- Lap DPM sheets by at least the specified minimum at every joint and seal them, and carry the membrane up the surrounding walls rather than stopping it flush at floor level.
Common Mistakes
- Dumping the full fill depth in one layer instead of compacting it in thin lifts, leaving the base soft and prone to later settlement.
- Ordering the compacted (finished) volume of fill material instead of the loose volume, running short on site.
- Laying the DPM directly over compacted fill instead of over a smooth PCC bed, risking punctures from sharp stones.
- Skipping the lap/overlap at DPM joints, leaving a path for ground moisture to reach the floor above.
- Treating the PCC bed as structural and skipping proper reinforcement checks on the actual floor slab above it, which does carry load.
Limitations
- Estimates material quantity for compacted fill, a PCC bed, and DPM only — does not include the floor slab/screed or any flooring finish above the DPM; use this site's Floor Screed or Tile calculators for those.
- Does not perform a geotechnical assessment — doesn't check whether fill is an appropriate solution for your site's actual soil bearing capacity or water table.
- Uses a single compaction percentage for the whole fill depth rather than modeling each compaction lift individually.
- Fill material density/compaction presets are commonly cited defaults, not a substitute for your supplier's actual test data.
- In "Multiple Different-Sized Sections" mode, only the footprint (length × width × count) varies by row — fill depth, fill material, PCC thickness/mix, and DPM settings are shared across every section. If fill depth genuinely differs by room, run the calculator separately for that room instead.
- Cost excludes labour, transport, and wastage/offcuts beyond the calculated quantities.
Related Construction Calculators
You may also find these calculators useful for foundation and floor base work:
- Backfill Calculator
Estimate backfill, compaction, truckloads, and cost.
- PCC Calculator
Estimate cement, sand, and aggregate for any plain cement concrete bed.
- Waterproofing Calculator
Roof, bathroom, basement, and membrane waterproofing beyond DPM.
- Floor Screed Calculator
Estimate cement and sand for the floor screed above the DPM.
- Concrete Footing Calculator
Estimate concrete for the footings this plinth sits on.
- Aggregate Coverage Calculator
General sub-base and aggregate coverage for other site works.