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Roof slab (lenter) calculator
Work out the concrete, cement bags, sand, crush and steel for a roof slab, the shuttering under it, and what it all costs at September 2026 rates, in total and per sq ft. For homeowners budgeting a roof and site engineers ordering for one.
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Calculator
Work out your lenter
Give the slab's size and thickness and any beams under it. The answer is the concrete, cement, sand, crush and steel to buy, the shuttering, and the cost at September 2026 rates.
Your lenter
- Concrete
- 439.2 cft416.7 in the slab and 22.5 in the beams
- Steel
- 1,100 kg1.1 tons, 1.1 kg a sq ft of slab, beams included
- Cement
- 79 bags50 kg bags, 1:2:4 (M15)
- Shuttering
- 1,060 sq ftThe underside, and 60 sq ft of beam sides
Materials to buy
- Cement50 kg bags, 2% over for waste
- 79 bags
- Sand2.03 trolleys of 100 cft, 5% over
- 202.9 cft
- Crush4.06 trolleys of 100 cft, 5% over
- 405.8 cft
- Steel1.1 tons
- 1,100 kg
- WaterTo mix, at 0.5 of the cement's weight; more for curing
- 1,932 litres
Cost at September 2026 rates
- Cement79 bags at Rs 1,600
- Rs 126,400
- Sand202.9 cft at Rs 80 a cft
- Rs 16,232
- Crush405.79 cft at Rs 188 a cft
- Rs 76,289
- Steel1,100 kg at Rs 262 a kg
- Rs 288,200
- Shuttering1,060 sq ft at Rs 55 a sq ft
- Rs 58,300
- Labour1,000 sq ft of slab at Rs 55 a sq ft
- Rs 55,000
- Cost
- Rs 620,421
Quantities and cost for budgeting, at Lahore rates as of September 2026. The thickness, the beams and the bars come from the structural engineer's drawings. Leaves out conduits laid in the slab, binding wire, the polythene sheet, waterproofing and the parapet.
Reference
Materials for 1,000 sq ft of slab
Concrete, cement, sand and crush to buy for a plain slab at each usual thickness, waste included.
| Thickness | Concrete (cft) | Cement (bags) | Sand (cft) | Crush (cft) |
|---|---|---|---|---|
| 4.5 in | 375 | 68 | 173.3 | 346.5 |
| 5 in | 416.7 | 75 | 192.5 | 385 |
| 6 in | 500 | 90 | 231 | 462 |
| Thickness | Concrete (cft) | Cement (bags) | Sand (cft) | Crush (cft) |
|---|---|---|---|---|
| 4.5 in | 375 | 86 | 165.4 | 330.8 |
| 5 in | 416.7 | 96 | 183.8 | 367.5 |
| 6 in | 500 | 115 | 220.5 | 441 |
Beams below the slab add their own concrete. Sand and crush come in 100 cft trolleys.
Reference
Steel in a sq ft of slab, by bar layout
What common slab layouts weigh, before the extra bars over supports and the beams.
| Bars | kg a sq ft | 1,000 sq ft with 5% laps (kg) |
|---|---|---|
| 3 sutar every 6 in, both ways | 0.68 | 716 |
| 4 sutar every 9 in, 3 sutar every 9 in | 0.63 | 663 |
| 4 sutar every 6 in, 3 sutar every 9 in | 0.83 | 875 |
| 4 sutar every 6 in, both ways | 1.21 | 1,273 |
A whole lenter, with its cranks, extra bars and beams, usually comes to 0.9 to 1.3 kg a sq ft. Two layers of mesh weigh twice one.
How it is worked out
From slab size to materials and cost
The concrete is the slab's area times its thickness, plus the part of each beam that hangs below it: the rest of the beam is inside the slab and already counted. A 40 x 25 ft roof at 5 in holds 416.7 cft, and two 15 ft beams 9 in wide and 12 in below it add 22.5 cft.
Wet concrete shrinks as it is mixed and packed, so the dry cement, sand and crush that make it come to 1.54 times its volume. That is split by the mix, 1 part cement to 2 of sand and 4 of crush for 1:2:4, and a 50 kg bag of cement is 1.25 cft. The cement to buy is 2% more, rounded up to whole bags, and the sand and crush 5% more, the same rules as the Material Planner in Smart Construction.
Steel comes from the drawing. Before there is one, a house lenter takes 0.9 to 1.3 kg a sq ft of slab with its beams, and 1.1 kg is typical in 2026 estimates. With the drawing, count the bars: main bars across the short span at their spacing, distribution bars along the long side, each weighed by its size, plus 5% for laps and bends and 3% for waste. Beam bars are on the beams' own bar bending schedule.
Shuttering is measured under the whole slab, the way contractors price it, plus the two sides of every beam below it. A beam's bottom takes the place of the slab's underside above it, so it adds nothing more.
The cost uses Lahore rates checked in September 2026: cement at Rs 1,600 a bag, sand at Rs 80 and crush at Rs 188 a cft, steel at Rs 262 a kg, shuttering at Rs 55 a sq ft, and Rs 55 a sq ft of slab for fixing the steel and pouring. Change any of them to your own. Conduits laid in the slab, binding wire, the polythene sheet and the waterproofing on top are left out.
The slab's thickness, its beams and its bars are for the structural engineer to set, from the spans, the loads and the building code. The calculator works out quantities and cost from them; it does not design a slab or check one.
On site
Terms you will hear
- Lenter
- The reinforced concrete roof slab of a house, also written lanter or linter, and the same slab over each floor of a house with more than one storey.
- Shuttering
- The formwork the slab is poured on: steel sheets or ply on props, hired by the sq ft and struck once the concrete has gained its strength.
- Main and distribution bars
- Main bars run across the short span and carry the load; distribution bars run the other way on top of them, hold them in place and spread the load.
- Crank
- A main bar bent up near a support, so it runs along the bottom in the middle of the span and along the top over the wall or beam.
- Cover
- The concrete between the bars and the surface, about 3/4 in under a slab, which keeps the steel from rusting and fire from reaching it.
- Crush
- The crushed stone in concrete, also called bajri, sold by the cft and the 100 cft trolley like sand.
Questions
Roof slab questions
Still have a question?
Ask our team during Pakistan business hours, in English or Urdu.
+92 333 2466662Chat on WhatsAppWhat does a lenter cost per sq ft in 2026?
About Rs 620 a sq ft for a 5 in roof slab with two beams, materials, shuttering and labour together, at Lahore rates as of September 2026. Contractors quoted Rs 550 to Rs 750 a sq ft in 2026, depending on the city, the thickness and the steel. Steel is the biggest part, about 46% of the cost.
How much steel is used in a roof slab per sq ft?
A house lenter takes about 0.9 to 1.3 kg a sq ft of slab, beams included, and 1.1 kg is typical: about 1,100 kg, 1.1 tons, for a 1,000 sq ft roof. The slab's own mesh is lighter: one layer of 4 sutar bars every 6 in with 3 sutar bars every 9 in is 0.83 kg a sq ft before laps. The bar layout on the structural drawing gives the real figure.
How many bags of cement does a 1,000 sq ft lenter need?
75 bags for a 5 in slab in 1:2:4, with 192.5 cft of sand and 385 cft of crush, waste included. A 6 in slab takes 90 bags, 231 cft of sand and 462 cft of crush. Beams below the slab add to these.
How thick should a roof slab be?
Most house roofs in Pakistan are 5 or 6 in thick, and 4.5 in is used over small rooms and verandas. The thickness depends on the span and the load, so it comes from the structural engineer: a wider room needs a thicker slab or a beam under it.
Which mix is used for a lenter, 1:2:4 or 1:1.5:3?
1:2:4 is the usual mix for a house roof. 1:1.5:3 is stronger and takes about 28% more cement: 96 bags for 1,000 sq ft at 5 in against 75. Use the mix on the drawing.
How is shuttering for a lenter measured and priced?
By the sq ft: the underside of the slab and the sides of the beams below it. Steel shuttering cost about Rs 55 a sq ft in Lahore in September 2026, hire and fixing together: the hire alone runs Rs 15 to 25 a sq ft for 30 days and the fixing Rs 25 to 40.
What does the lenter cost leave out?
It covers the concrete materials, the steel, the shuttering and the labour to fix the steel and pour. Electrical conduits laid in the slab, binding wire, the polythene sheet under the concrete, waterproofing and the parapet are extra, as is the engineer's fee.
Plan the materials for the whole house
Smart Construction plans every part of a building from the foundations to the roof, prices it at the rates you actually pay and follows the buying on site.
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