Floor usage	Distributed load (kN/m²)	Concentrated load (kN)
Type 1: self contained dwellings	1.5	1.4
Type 2: Apartment houses, boarding houses, hotels, residential clubs, block of flats .
Boiler rooms, motor rooms, fan rooms and the like.	7.5	4.5
Communial kitchens, laundries	3	4.5
Dinning, lounges, billiard rooms	2	2.7
Toilet rooms	2
Bedroom, dormitories	1.5	1.8
Corridors, stairs, landings, foor bridges, balconies	3	4.5
Type 3: Hotels & Motels
Boiler rooms, motor rooms, fan rooms and the like. Including weight of machinery	7.5	4.5
Assembly areas without fixed sitting, dancehall bars	5	3.6
Assembly areas with fixed sitting	4
Corridors, stairs, hallways, landings, footbridges etc	4	4.5
Kitchens, laundries	3	4.5
Dinning, lounges, billiard rooms	2	2.7
Bedrooms	2	1.8
Toilet rooms	2
Balconies	4

In this article, the following questions will be answered.

• What is concrete?
• What is reinforced concrete?
• Strength of concrete.
• Concrete mix ratio for reinforced concrete.
• Types of Steel used for reinforced concrete.
•  letter codes for reinforcement steel.
• Code of practice.
• Structural layout.
• Prior mathematical knowledge.

What is concrete?

Concrete is produced by the mixture of cement, sand, graded stones and water. It hardens to a solid mass in 28 days.

What is reinforced concrete?

Reinforced concrete is simply concrete structure that has been strengthened with steel.

Strength of concrete ( for reinforced concrete)

The strength  is  concrete that  is the accepted standard for reinforced concrete is 24 kN/mm²

Concrete mix ratio for reinforced concrete 

The standard mix ratio for reinforced concrete is 1:2:4. That is, 1 part of cement to 2 parts of fine aggregates (sand) to 4 parts of coarse aggregates ( graded stones/gravel/granite)

Types of steel used for reinforced concrete.

1. Mild steel: have strength (fy) of  250 N/mm²
2. High yield steel: have strength (fy) of 460 N/mm² 

High yield steel is more economical and is mostly used for reinforced concrete design.

Letter codes for reinforcement steel

R for mild steel

Y for high yield steel  (type 1 bars)

T for high yield steel (type 2 bars)

Square twisted high yield bars are type 1 while ribbed bars are type 2.

Code of practice

There are many codes of practice for reinforced concrete however the code used in this article is BS 8110.

BS 8110 is the former British code used for reinforced concrete design.

Every country or region has their own design code or uses adopted code from other countries or regions.

Structural layout

Structural layout is the drawing derived from architectural drawing. It shows  the arrangement of reinforced concrete structural elements such as slabs ,beams and columns and how these elements support the building structure. Structural layout must is done in such a way that it is;

1.Sensible

2.the structural elements are economically arranged.

3. It does not distract or change the original design of the architect except where absolutely necessary and that is after consultation with the architect. 

Prior mathematical knowledge 

You should have learnt how to calculate shear forces and moments of framed structures.

Asphalt
Roofing 19mm thick	42 Kg/m²
Damp-Proofing 19mm thick	41 Kg/m²
Road & Footpath 19mm thick	44 Kg/m²
Bitumen Roofing Felt
Mineral Surface Bitumen	3.5 Kg/m²
Blockwork
Solid 25mm thick stone aggregate	55 Kg/m²
Areated 25mm thick stone aggregate	15 Kg/m²
Board
Blockboard 25mm thick	12.5 Kg/m²
Brickwork
Solid clay 25mm thick	55 Kg/m²
Solid concrete 25mm thick	59 Kg/m²
Cast stone	2250 Kg/m³
Concrete	2400 Kg/m³
Flagstones
Concrete 50mm thick	120 Kg/m²
Glass fibre
25mm thick slab	2 – 5 Kg/m²
Gypsum panels and partitions
Building panels 75mm thick	44 Kg/m²
Lead
Sheet 2.5mm thick	30 Kg/m²
Linoleum
3 mm thick	6 Kg/m²
Plaster
Gypsum. 13mm thick	22 Kg/m²
Plastic sheeting corrugated	4.5 Kg/m²
Plywood ( per mm thick)	0.7 Kg/m²
Reinforced concrete	2400 Kg/m²
Rendering
Cement : sand (1:3) 13 mm thick	30 Kg/m²
Screeding
Cement : sand (1:3) 13 mm thick	30 Kg/m²
Slate tiles
(Depending upon thickness & source)	(24 – 78) Kg/m³
Steel
Solid mild steel	7850 Kg/m³
Corrugated roofing sheets per mm thick	10 Kg/m²
Tarmacadam (25 mm thick)	60 Kg/m²
Terrazzo (25 mm thick)	54 Kg/m²
Tiling / roof
Clay	70 Kg/m²
Timber
Softwood	590 Kg/m³
Hardwood	1250 Kg/m³
Water	1000 Kg/m³
Wood wool
Slabs 25mm thick	15 Kg/m²

Unit Mass of Building Materials