Imposed Loads for Residential Buildings

Floor usageDistributed load (kN/)Concentrated load (kN)
Type 1: self contained dwellings 1.51.4
Type 2: Apartment houses, boarding houses, hotels, residential clubs, block of flats .
Boiler rooms, motor rooms, fan rooms and the like.7.54.5
Communial kitchens, laundries34.5
Dinning, lounges, billiard rooms22.7
Toilet rooms2
Bedroom, dormitories 1.51.8
Corridors, stairs, landings, foor bridges, balconies 34.5
Type 3: Hotels & Motels
Boiler rooms, motor rooms, fan rooms and the like. Including weight of machinery7.54.5
Assembly areas without fixed sitting, dancehall bars 53.6
Assembly areas with fixed sitting4
Corridors, stairs, hallways, landings, footbridges etc44.5
Kitchens, laundries 34.5
Dinning, lounges, billiard rooms22.7
Bedrooms21.8
Toilet rooms2
Balconies4

Brief Introduction to Reinforced Concrete Design

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.

Unit Mass of Building Materials based on BS 648

Asphalt
Roofing 19mm thick42 Kg/m²
Damp-Proofing 19mm thick41 Kg/m²
Road & Footpath 19mm thick44 Kg/m²
Bitumen Roofing Felt
Mineral Surface Bitumen 3.5 Kg/m²
Blockwork
Solid 25mm thick stone aggregate55 Kg/m²
Areated 25mm thick stone aggregate 15 Kg/m²
Board
Blockboard 25mm thick12.5 Kg/m²
Brickwork
Solid clay 25mm thick55 Kg/m²
Solid concrete 25mm thick59 Kg/m²
Cast stone 2250 Kg/m³
Concrete2400 Kg/m³
Flagstones
Concrete 50mm thick120 Kg/m²
Glass fibre
25mm thick slab2 – 5 Kg/m²
Gypsum panels and partitions
Building panels 75mm thick44 Kg/m²
Lead
Sheet 2.5mm thick30 Kg/m²
Linoleum
3 mm thick 6 Kg/m²
Plaster
Gypsum. 13mm thick22 Kg/m²
Plastic sheeting corrugated4.5 Kg/m²
Plywood ( per mm thick)0.7 Kg/m²
Reinforced concrete2400 Kg/m²
Rendering
Cement : sand (1:3) 13 mm thick30 Kg/m²
Screeding
Cement : sand (1:3) 13 mm thick30 Kg/m²
Slate tiles
(Depending upon thickness & source)(24 – 78) Kg/m³
Steel
Solid mild steel 7850 Kg/m³
Corrugated roofing sheets per mm thick10 Kg/m²
Tarmacadam (25 mm thick)60 Kg/m²
Terrazzo (25 mm thick)54 Kg/m²
Tiling / roof
Clay70 Kg/m²
Timber
Softwood590 Kg/m³
Hardwood1250 Kg/m³
Water1000 Kg/m³
Wood wool
Slabs 25mm thick15 Kg/m²

Unit Mass of Building Materials

Typical Imposed Loads for Residential Buildings

Typical live loads of different types of buildings. Handy information for civil or structural engineers.

Self contained dwelling units;   1.5 kN per meter squared.

For public buildings where there is a tendency for many people to be in the building at once. For example;boarding houses, lodging houses, guest houses, hostels, residential clubs and communal areas in blocks of flats Boiler rooms, motor rooms, fan rooms and the like including the weight of machinery;  7.5kN per meter squared.

Communal kitchens, laundries;  3.0kN per meter squared.

Dining rooms, lounges, billiard room ; 2.0kN per meter squared.

Toilet Rooms; 2.0kN per meter squared.

Bedroom, Dormitories; 1.5kN per meter squared.

Corridors, hallways, stairs, landings, footbridges; 3.0kN per meter squared.

 Hotels and motels Boiler rooms, motor rooms, fan rooms and the like, including the weight of machinery ;  7.5kN per meter squared.

Assembly areas without fixed seating, dance halls, Bar; 5kN per meter squared.

Assembly areas with fixed seating;4kN per meter squared..

Corridors, hallways, stairs, landings, footbridges, etc; 4kN per meter squared..

Kitchen Laundries; 3kN per meter squared.

Dining rooms, lounges, billiard room; 2kN per meter squared.

Bedrooms., Toilet rooms ; 2kN per meter squared.

Strength of Common Building Materials

Building materials

Here are strength of some common building materials based on BS 648. This is useful information for civil/structural engineers

Asphalt 

Roofing 2 layers; 19 mm thick,  42 kg per meter square.

Damp-proofing; 19 mm thick, 41 kg per meter square.

Roads and footpaths; 19 mm thick 44 kg per meter square.

Bitumen roofing felts 

Mineral surfaced bitumen;     3.5 kg per meter square.

Blockwork 

Solid per 25 mm thick stone aggregate ;  55 kg per meter square.

Aerated per 25 mm thick;        15 kg per meter square.

Board

Blockboard per 25 mm thick;   12.5 kg per meter square.

Brickwork 

Clay, solid per 25 mm thick;     55 kg per meter square

Medium density Concrete, solid per 25 mm thick;   59 kg per meter square.

Cast stone;  2250 kg per meter cubic.

Concrete 

Natural aggregates;   2400 kg per meter cubic.

Lightweight aggregates (structural); 1760 + 240/ −160 kg per meter cubic.

Flagstones 

Concrete 50 mm thick;   120 kg meter square.

Glass fibre 

Slab, per 25 mm thick; 2.0–5.0 kg meter square.

Gypsum panels and partitions 

Building panels 75 mm thick;    44 kg meter square.

Lead 

Sheet, 2.5 mm thick;    30 kg per meter square.

Linoleum 

3 mm thick; 6 kg per meter square.

Plaster

Two coats gypsum; 13 mm thick;    22 kg per meter square.

Plastics sheeting (corrugated);   4.5 kg per meter square.

Plywood

per mm thick;    0.7 kg meter square.

Reinforced concrete;     2400 kg meter cubic.

Rendering 

Cement: sand (1:3), 13 mm thick;   30 kg per meter square.

Screeding 

Cement: sand (1:3), 13 mm thick; 30 kg per meter square.

Slate tiles 

(depending upon thickness and source);  24–78 kg per meter cubic .

Steel 

Solid (mild); 7850 kg per meter cubic.

 Corrugated roofing sheets; 10 kg per meter square per mm thick.

Tarmacadam ;

25 mm thick 60 kg per meter square.

Terrazzo; 

 25 mm thick 54 kg per meter square.

Tiling, roof 

Clay; 70 kg per meter square.

Timber 

Softwood;  590 kg per meter cubic .

Hardwood; 1250 kg per cubic meter.

Water; 1000 kg per meter cubic.

Woodwool

 Slabs; 25 mm thick 15 kg per meter square.

Note: to convert to Newtons per millimeter square; Multiply the amount in kg by 10 and then divide by 1000

Road Construction Within Housing Estate

estate road

Road construction  within a housing estate is necessary to provide standard access road and driveways into private dwellings. This type of road construction  is on a small scale. The construction of these types of roads will be discussed under three aspects;

  1. Setting out
  2. Earthworks 
  3. Pavement construction.

Setting out

Setting out means the establishment of center, width, existing level and formation level of the road. This activity is usually carried out after top soil removal. The layout can include straight lengths, turning bays and intersection curves. Drainage positions must  be adequately set out as well.

Road center  points, widths and levels can be set out using traditional methods with the aid of levelling instrument/ theodolite/ total station, ranging rods,levelling staff, measuring tapes, pegs, markers and so on.

Earthworks

 After proper setting out has been done. Existing  and formation levels, determined and marked out, earthworks can begin. Earthworks involve the movement of earth to and from sections of the road in such a way that the formation levels/ design levels of the road is achieved. This process is also carried out for the road’s drainage as well.

Pavement construction 

The earthworks prepare the subgrade. Once drainage and other buried services have been installed, pavement construction can commence. There are two types of pavements; flexible and rigid pavements.

Flexible pavements consist of materials that are applied in layers over the subgrade. Rigid pavement consist of concrete slab resting on to of a prepared subgrade the construction of flexible pavement should consists of the following layers.

Section of a typical flexible pavement

A sub base layer of about 100mm thick on the subgrade. The sub base can consist of crushed stone or dry lean mix concrete followed by a surfacing layer of asphalt which can be around 60mm thick.