- SAND / CEMENT MIXTURE
In the making of blocks for building, it very important to consider the number of blocks to be molded per cement bag, if you are using hollow blocks that call for higher concentration of cement to the sand. Why it is better you mold the blocks yourself if to be sure of the quality of what you are putting on the ground, some molders in Nigeria can 6inch block 30pcs per a bag of cement while some for-profit purpose can mold 45peices per a bag of cement believe me these two blocks can never be of the quality both in strength and durability.
The worst that could happen to a builder is; if the blocks are purchased from block industries and their mixture ratio is unknown, as well as their method of compression, especially if it is not good enough, you may end up building a structure that could collapse at any moment, hence if you are a builder and wants to use blocks from block industries it is very important to know the block industry supplying the block, their location and guarantee of quality, but the best is to visit the industry to see their cement and sand mixing ratio, their method of molding either with a machine or manual method.
IN Nigeria most block industries can produce a very good block with the required cement and sand ratio according to your request and money while some builders that want to save money would be seeking the ones with less price from these block industries at the end they end up having a counterfeit that is only highly compressed by the molding machine.
2 SOIL TEXTURE
The soil test of the ground you want to build a house is very important for the sustainability and integrity of the house. There many methods of checking for the soil texture but most engineers use this simple method of bringing a small sample of the sand squeezing it in their palm forming a ball or round shape of that sand with the addition of little or no water then placing it inside a bow having a clean water inside it to cover the round shaped soil in it, the period it takes for the sand to dissolve inside the water will be timed with a stopwatch to obtain the texture of that particular soil.
This text is very crucial before erecting any structure on that soil because if the soil dissolved quickly in the water it means it a sandy soil or contains more properties of sand soil which mean more attention is to be placed on erecting the foundation using many support techniques, but in the case of the sand taking a very long time to dissolve it means it is a muddy sand which is very good in erecting a structure, such sand only need a good digging for the foundation.
It is always good as an engineer to know the soil texture you are building on especially if the building will upstairs like a duplex, multiple stairs building.
- POSITIONING OF BUILDING
Every land has the four cardinal points located on it which are the south, north, east and west, an engineer should use appropriate wind detecting device to access the wind movement on the site location, know the wind direction as well as speed in the morning, afternoon and night, if there will be enough chance you can even take the data for the four annual seasons, i.e.; autumn, summer, spring, & winter.
Though the effects of the wind on the building are not so visible, but a very tall building positioned against the wind direction, the foundation will act in form of silent vibration each time the wind is very high, thus the weakening of the foundation, this is why the wind must be put into consideration. The only way to reduce the effects of the wind is to position the building in a way that would not stand against the incoming wind or streamline the position of the house at the direction the wind force is very high. Also enough strength must be given to foundation of the building.
- POOR QUALITY OF CONCRETE
A standard concrete has to be the standard ratio for the method of forming a concrete for pillars and decks of buildings. Note; there is a big difference between mixture for block making and that of concrete, Concrete is what we use in forming the pillars, foundations, and the decks of the building (for tall buildings.)
The standard concrete ratio is 1 Cement bag (50kg): 2 Sand: 3 gravel, what this simply means is that your concrete is supposed to have more gravel in percentage than sand, but for economic reasons most builders violet this standard due to the fact that gravel is more costly than sand, or for other reasons.
Most builders use 1 bag of cement: to 6-8 buckets (20litres size buckets) of sharp sand, then to 10-12 buckets (20litres size buckets) of gravel (limestone, or ironstone).
They are properly mixed and added enough water to obtain a good mixture. Please note; too much water can destroy the strength of the concrete as some portions of cement which act as binder would flow away after pouring the concrete leaving only sand and gravel, hence it is advisable to watch the water you are adding and stop once you observe the concrete to be mixable with a shovel or concrete mixing machine. Meanwhile, poor water condition or insufficient water in the concrete can make it very difficult to mix, and causes porosity in the pillars after pouring, also can cause the concrete to be non-uniform after the mixing.
It is necessary you use a vibrator or poker while pouring a concrete to ensure the whole content goes inside to form the pillars, foundation, etc. leaving no room for porosity after the drying of the concrete, besides the avoidance of porosity these machines enhance the surface finish of the concrete. It IS necessary to ensure the gravels size are reduced very well to ensure lack of porosity in the concrete and good surface finish.
Having obtained a good concrete mixing method it is important to put into consideration of the facts that method and size of the rods in which the concrete is to be poured speak volume about the integrity of the pillars, decks, etc. Hence it is very necessary that a good iron or steel rod binding method be used and ensuring the size of the rod is according to the capacity of the load the pillar, decking, foundation, etc., would carry when subjected to use for forever, this is why proper considerations and calculations must be given to this section.
- ABANDONING BUILDINGS UNDER CONSTRUCTION FOR A VERY LONGTIME.
Most buildings are abandoned after reaching a particular stage due to the shortage of finance or for some other reasons. But whatever the reason may be a building is not good to be left half way, the blocks that are laid to form the walls of the uncompleted building will be exposed to the continues rainfalls during the raining season, the hot sun during the dry season and other harsh weather conditions which will assist in the weakening of the strength of the walls thereby forming a long transverse crack on the wall.
The cracks a5rre not the only problem developed by an abandoned building, the cases of the top block layers being washed off as a result of continuous rainfall and the movement of reptiles like a lizard at it surfaces also contribute to the washing off.
A building left for a very long time uncompleted tends to lose its hold on the blocks forming the walls of the building hence a particular block of any wall can easily fall at any serious vibration of the wall, this is very common the case of an uncompleted building that the roofing components is not yet fixed.
Most Nigerian builders do not put these factors into place hence they encourage the client to proceed with the guarantee that the long-term abandoning of the structure has not affected it strength, and this advice sounds good in the ear of most clients as it serves to save more money for the building projects.
If you want to build a good house or structure please ensure you complete it to plastering level within five years interval because of anything more than that the integrity of that structure cannot be guaranteed.
- EROSION AND FLOODS
One of the problem in most Nigeria environment is the seasonal rise in water level which most times causes flooding of the environments, houses, and farmlands, etc. this usually occur from July to November of every year; though not every part of the country in involve but the one that occurred in the year 2012 was so much that houses, roads, and other structures were covered with flood for months in almost different locations of 20 states out of the 36 states in the country, it was noted that immediately after the flood disappeared most of the Nigeria road became unmovable, the current of moving water that followed the flood was able to carry many household properties to big rivers where they are lost forever, while most building roofs was completely removed by the flood, the same force that followed the moving caused the wall of most building to collapse while some got cracked immediately after the flood.
This is why flood contributes to one of the reasons why most Nigeria building collapse as most builders do not put this factor into consideration when the building projects is ongoing, while those that put it into consideration will have their structures standing very strong even after the flood has occurred for many years.
Another contributor is the rainfall; during the serious rainfall season that usually comes with mighty wind, the structures are subjected to serious threats by the erosion that follows the rainfall thereby causing washing away of most of the soil and creating a big environmental deformation and uneven soil surface.
- DEEP ROOTED TREES
It is a common thing in a typical Africa environment to have trees around the building to act either as a shield for resting outside the house or to become a source of supply for fruits like ; mangoes trees, cashew trees, avocado pear trees, orange and coconut trees, etc., while all these are good and healthy it is important to note that when the roots of these trees has grown so deep and wide, and if they are very close to any part of the building they exert a great force on that part of the building, hence causing either crack or weakening of the part of that building. If such trees are left further to grow very wide in size the cracks created on the ground could extend to the height of the building, and that will be another source of building collapse.
If a building is located very close to where earth breaking and heavy duty equipment or machine is operated such as the factory, railway, and construction industries, etc. the building foundation will be subjected to constant vibration which then weakens the foundation over a period of time.
The effect of vibration in the collapse of buildings is not an instant action, it is a long time damage to building foundations that gradually surface after a long period of time.
Just like any other structure when a building is accidentally stroke by any heavy object like trees, masks, etc. maybe they fall as a result of the wind or other causes. Many factors give rise to accidental collapse building in Nigeria but the most common of them is that of falling objects like trees, etc. and this is the reason why most Nigeria builders and engineers consider the surrounding of any land before putting building in it, and many engineers do not encourage having deep root trees within the compound, except at a very far distance from the building.
- ECONOMIC REASON
The important of the economy in building project cannot be overlooked, but that should not be placed above the safety and the durability of the house. Most builders economize to the detriment of the owner of the by using substandard and low priced materials which end up putting the house in an unsafe situation which exposes it to collapse easily by any of the factors that cause building collapse, this is the major cause of most building collapse in Nigeria.