TryBuildCalcPlinth Filling Calculator for House House plinth fill, PCC bed, and DPM estimator
Calculate compacted soil fill, PCC bed, and DPM quantity for a house plinth.
🕒 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 120.00 m² (1,292 sqft) plinth footprint filled 200 mm deep with soil / select fill, you need approximately 50.72 tonnes of fill material and 9.450 m³ (333.7 cft) of PCC bed concrete.
Compacted Fill
Material: Soil / Select Fill
Compacted volume: 24.000 m³ (847.6 cft)
Loose volume (before wastage): 27.600 m³ (974.7 cft)
Loose volume (with wastage): 28.980 m³ (1,023.4 cft)
Material to order: 50.72 tonnes
PCC Bed (1:4:8)
Thickness: 75 mm
Total concrete: 9.450 m³ (333.72 cft)
Cement: 32.3 bags
Sand: 4.478 m³ (158.1 cft)
Aggregate: 8.956 m³ (316.3 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
Looking for the verification checklist, reference tables, or tips and mistakes?See the complete Plinth Filling Calculator.
House plinth filling estimate
This page is set up for a typical residential plinth: a 12 m x 10 m footprint (120 m²) filled with the default soil fill at a 200 mm compacted depth. That works out to 24 m³ of compacted fill, which needs 28.98 m³ of loose material once the 15% compaction and 5% wastage allowances are applied — roughly 50.7 tonnes to order from your supplier.
On top of that fill, the default 75 mm PCC bed at a lean 1:4:8 mix needs 9.45 m³ of wet concrete (with 5% wastage) — about 32.3 cement bags — plus sand and coarse aggregate split by the mix ratio. DPM isn't included by default on this page; switch it on if your project specifies a membrane before the floor slab.
- Default footprint: 12 m x 10 m (120 m²).
- Fill: 200 mm soil, 15% compaction, 5% wastage → 50.7 tonnes.
- PCC bed: 75 mm, 1:4:8 mix, 5% wastage → 9.45 m³ (32.3 bags).
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 | 12 m × 10 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 | 12 m × 10 m | 120.000 m² |
| Total area | 120.00 × 1 | 120.000 m² (1,291.67 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 | 120.00 m² × 200mm | 24.000 m³ |
| Loose volume | 24.000 m³ × 1.15 | 27.600 m³ |
| Loose volume (with wastage) | 27.600 m³ × 1.05 | 28.980 m³ (1,023.4 cft) |
| Order quantity | 28.980 m³ × 1750 kg/m³ ÷ 1000 | 50.72 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 | 120.00 m² × 75mm | 9.000 m³ |
| With 5% wastage | 9.000 × 1.05 | 9.450 m³ (333.7 cft, 32.3 bags) |
Step 5 — Cost & Contingency
| Calculation | Substitution | Result |
|---|---|---|
| Enable cost estimation above to see fill, PCC, and DPM cost | — | |
Therefore, this 120.0 m² plinth needs approximately 50.72 tonnes of fill material, 9.450 m³ of PCC bed concrete.
This page keeps things focused on the calculation above. For the full construction guide — verification checklist, reference tables, usage steps, tips, common mistakes, and limitations.See the complete Plinth Filling Calculator.