Buying of Building Materials for Home Improvement Projects
There has been an increase in the number of DIY outlets in recent years and the competition between them is fierce. DIY enthusiasts are now able to buy materials at levels that were previously only available to trade customers.
Most of these stores will deliver materials to your home or you can hire one of their vans on an hourly basis. Although ordering most materials is fairly straightforward, there are some items that require a little more thought.
Concrete is an example. Unless you go to a ready mix concrete firm, you cannot buy a cubic metre of concrete, only the ingredients. Details of how much to order are given under the heading of Concrete work.
Another factor that must be considered when ordering is making an allowance for waste because it would be unusual if you were able to place the exact amount of material that you had ordered.
Excavation Building Materials
Excavated material bulks after it has been dug out, i.e. it occupies a greater volume after excavation than it did in the ground. It would be a mistake to order a skip sized six cubic metres if the pre-excavated volume of earth was also six cubic metres.
The following figures represent the average amount of bulking that takes places for various types of earth.
Sand and gravel 10-15%
Hard materials, rock 40-50%
Mixing Ratios for Concrete
Although most people's perception of concrete is that of a basic building product, it is highly complex and research is constantly being undertaken to find out more about this versatile material. In domestic building work the two most commonly-used mixes are 1:2:4 and 1:3:6.
The numbers refer to the proportion by volume of cement, sand and aggregate used in the mixes. 1:2:4 mix is usually placed in paths, floors and walls whilst 1:3:6 is predominately used in foundations. These ingredients are usually sold by weight and the following table gives the amount of material needed to mix one cubic metre of concrete.
1:2:4 mix 1:3:6 mix
Cement 240kg 170kg
Sand 520kg 550kg
Aggregate 950kg 1,000kg
Take a simple example. You intend to lay a foundation to a garden wall and the dimensions are 9000 mm long by 300mm wide and 150mm deep. Multiplying these figures produces avolume of 0.41 cubic metres. The foundation would be 1:3:6 mix so you would need to order the following quantities of material to complete the work. Note that these figures include a 5% allowance for waste.
170kg x 0.41m3 + 5% = 73kg
550kg x 0.41m3 + 5% = 237kg
1,000kg x 0.41m3 + 5% = 430kg
It is unlikely that you will be able to buy the exact quantities you need but the above figures should help to reduce any unnecessary waste. Sand is sometimes sold by volume instead of weight so you may need to adjust the above figures accordingly - there are 1,600kg in a cubic metre of sand.
Ready Mixed Concrete
For larger jobs, such as laying a concrete drive, it is probably better to have the concrete delivered ready mixed. This a very competitive market so shop round for quotations. Concrete is usually delivered in four, five or six cubic metre loads and you will pay extra per cubic metre for delivering ‘air' - this is the term used in the industry for part loads. Some firms specialise in small orders and they usually advertise their services in Yellow Pages. It is worth preparing some part of your garden, such an uncompleted path or a base for a shed, to receive any concrete left over.
Brickwork Building Material
The thickness of brick walling is usually described as half brick thick (102.5mm) or one brick thick (215mm thick). There are many different ways of arranging laid bricks, called the bond, but in most domestic building situations a stretcher bond is the most common. here are 62 bricks per square metre in a half brick wall and 124 in a one brick wall. These figures include a 5% allowance for waste. The question of ordering materials for mortar is a little more complicated but the following figures should help.
Brickwork is usually laid in cement or gauged mortar. Cement mortar is normally used in foundation walls for extra strength and consists of one part of cement to three parts of sand (1:3). Gauged mortar is used in most other work and is made up of one part of cement, one part of lime and six parts of sand (1:1:6).
Here are the dry weights of materials per cubic metre of mixed material.
Cement mortar Gauged mortar
Cement 440kg 230kg
Lime - 120kg N/A
Sand 1,820kg 1,920kg
The average quantity of mortar needed in the construction of one square metre of a half brick thick wall is 0.03m3 and 0.06m3 for a one brick thick wall. If you are only building a small amount of brickwork, it may be better to buy the mortar already dry mixed but it is much cheaper to mix it yourself.
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