BuildingContractorSecrets.com

Question:

Oga, I have done casting and filling with laterite, do I need to use hardcore again or bricks before german floor. Is thought is just ramming the laterite.

Hardcore application in the building process is also as important as any of the key stages . Hardcore is reffered to as some measures of large aggregates of stones used as part of the foundation in a construction project. To simple put is bigger aggregates of what you call granites on site. Though some uses broken blocks /bricks, these are however not recommended because of their strenght, people only use them to save cement during casting of oversite/german concrete which is not advisable.

Hardcore is applied after you have filled the internal part of your foundation with laterite or sharpsand as the case may be, rammed and ready to apply iron rods/wire mesh and concrete. In the usage of hardcore, the textbook application is as shown in the image 1 below, there is a space entirely left for the hardcore as specified by the professional before the space for the concrete, this is standard or you call it textbook application, but getting the accurate thickness during construction for portion of concrete  is not always common because of crude method of construction, level of skill of the builder and the settlement pattern due to nature of soil. So what most people do onsite is as shown in image 2-the hardcore takes a portion of the concrete space so you only needs to fill the remaining parts with concrete.(Is not what is recommended but is what most do)

IMPORTANCE

(1)Hardcore strengthens or solidifies the base which the german concrete will sit on, thereby helps in resisting pressure of dead and live loads on the ground floor.

(2}It gives good base for building

(3)Is also part of foundation

(4)In the image 2 type of application, it helps to save cost of construction, the volume occupied by the hardcore if it were to be concrete it would have cost more.

(5)Is a gap between the german floor /oversite concrete and the earth so it helps to reduce movement of water up to the ground floor

(6)The air in between the hardcore if there is any will also help to reduce movement of water.

(7)In case of image 2, it reduces the time of casting because you are using lesser volume of concrete to when you are casting the entire mass.

Everybody desires a cost effective and affordable Borehole in his house, office, community , etc. However, have you ever wondered why the cost of borehole varies. In some areas, it costs as high as N500, 000, N1,000, 000 and even more, while some pay as low as N250, 000, N180, 000 and even N120, 000. I am here to give you a breakdown account for this. However, this does not rule out the fact that non professionals can issue a low quite to attract clients and deliver substandard work.
The cost of borehole is influenced by so many factors such as:

1. The Geology of the Environment:
The specific parameter to look out for here is the nature of formation in the sub surface and depth of water table. In the Niger Delta terrain where the depth of water table is as low as 150feet to 250feet, and even 80 feet, the cost of borehole varies between N120, 000 to N250, 000, but to get an accurate quote a proper geological survey is necessary or preliminary investigation is paramount to identifying the exact position of the water table.

2. Number of Casing: A casing is a lining given to a borehole to avoid collapse of the hole, interference of formation on the transmitted water, and more so, to prevent contamination with the aquifer. In an area where the water table is between 80ft to 250ft, you may require 8 to 25 number of casing, which unit cost is about N6, 000. So the more the casing, the more the cost of casing, which overall influence the overall cost of the borehole. For abore hole with water table depth of ove 1000feet, you can expect to pay more for the casing and more so bore hole construction.

3. Type of Drilling Equipment: There are 2 major equipment used for drilling equipment are the manual rig and the motorized rig depending on the parameters of interest. The tripod is used for the manual drilling and does not go beyond 250ft, and as such when you are drilling and does not go beyond this depth, you need the motorized rig. The cost of using a Tripod is N30, 000 for daily use, while for a motorized rig, you need N500, 000 for a daily use. This will overall impact on the cost of Borehole Construction. More so drilling a borehole in a basement terrain, clay or more difficult environment, we recommend a motorized rig. This rig is also required in terrain where water table is as high as 1000ft and more.

4. Type of Submersible Pump: There are types of submersible pumps used for borehole construction, depending on the expected pump rate for the borehole. This pump rate of this system is determined by the horsepower of each submersible pump. A submersible pump with a horsepower of 1.5 cost between N16, 000 and N20, 000 and will not add much to the cost of the borehole construction, but a pump of 9.0 and above horsepower, which cost N85, 000 and above, it will considerably add to the cost of borehole construction. We recommend a pump of 1.5 to horsepower for domestic use, and 9.0 horsepower submersible pump for a commercial pump.

5. Other factors include Water Analysis and Treatment, etc.
For more information on construction of borehole for domestic and commercial use, or to get an accurate quote for your next borehole construction, contact us on sales@platiniumglobalventures.com, or visit our website at

www.platiniumglobalventures.com. You can call us on 08095228397

I am obliged to write on oversite concrete based on comments and numbers of questions on it. For the question above the subscriber should be able to connect to the importance of oversite/german concrete after going through this article.

(1)It helps in preventing water from the soil from percolating to the surface thereby avoiding grow of algae around the building walls and on the floor. These buildings that suffers this most are in the waterlogged area however it doesn’t exempt buildings also in more stable areas.

(2)Oversite concrete helps to sustain the weight of live and dead loads (human,materials and the weight of the building itself) in the building in otherwords it contributes immensely to the structural elements of the building.

(3)It also helps in case of vibration. When there are engines in the house or outside that causes a lot of vibration it helps to spread the effects equally around the building to the bearest minimum.

(4)Oversite concrete also helps the foundation in sustaining the weight of the house, prevents cracks on blockwalls because of transmission of forces applied on it spreading round the entire span of building eqaually.

(5)It also gives good base for floor finishes like tiles,terrazzo,wood etc

(6)It prevents growth of plants inside the house from the soil.

(7)Also prevents termites,worm and other insects from the ground from gaining easy access from the earth.

Internationally accepted standard measurement is in meters, millimeters etc hence most drawings from present day architects are in millimeters. However many are used to measuring in feet and inches, therefore is important for you to convert a measurement done in S.I unit to feet and inches for a proper mental visualization of the space measurement.

Remember your primary school conversion

10 millimeter=1 centimeter

10 centimeter=1 decimeter

100 centimeter=1 meter

1000 millimeters=1 meter

1000 meters=1 kilometer

At spot approximately, one inch is taken as 25mm, hence to convert inches it will go in this format

1”=(25 x 1)=25mm

2”=(25 x 2)=50mm

3”=(25 x 3)=75mm

4”=(25 x 4)=100mm   e.t.c

So for a 6” block or thickness of concrete we are only saying (6” x 25)=150mm

Converting this to meters, remember  1000millimeter (mm) is 1 meter(m), therefore divide 150mm by 1000mm=0.15m. The same formula applies to others.

For feet we use approximately 3.3 feet to 1 meter, hence we usually goes in this order

1 meter=3.3 feet

2 meter=(2 x 3.3)=6.6 feet

3 meter=(3 x 3.3)=9.9 feet

4 meter=(4 x 3.3)=13.2 feet

5 meter=(5 x 3.3)=16.5 feet

6 meter=(6x 3.3)=19.8 feet    etc

These are close approximates to help in easily converting measurements from your drawing since most are familiar with inches and feet.

For areas of land you are to buy in Lagos is commonly 18 meters by 36meters or 60 feet by 120 feet though it may varies in some areas and for most of other states is 15 meters by 30 meters i.e 50 feet by 100 feet. So the area of a plot in Lagos is approximately 648m² i.e (18m x 36m) and for most of other states is 450m² i.e (15m x 30m)

Now to calculate areas of land,

An acre of land is approximately 4,047m²

An hectare is 100m by 100m piece of land which is equals to 10,000m²

An hectare of land is about 2.47 acres

An acre is approximately 0.405 hectare

Remember one plot is 648 m²

therefore to know how many plots in an acre is

4,047 m²/648 m²=6.245 plots. Approx 6 plots

However for the numbers of plots in an acre for a plot of 450 m²

is 4,047 m²/450 m²=8.9933 plots. Approx 9 plots

For the numbers of plots in an hectare therefore is

10,000 m²/648 m²=15.432 plots Approx 15 plots

Or simply put 6 x 2.47 acres =14.82 Approx 15 plots

And for a 450m² plot

10,000m²/450m² =22.22 plots. Approx 22 plots

Or simply put 9 x 2.47 acres=22.23 plots. Approx 22 plots

As usual I am prompted to write this article because of the fear of seeing a qs estimates concerning your building and for the disregard of the services of a quantity surveyor in Nigeria.

Advantages of QS estimate over others

1)A qs estimate gives you close to exact quantity though in area or volume of materials to be used, though the cost attached to the units may be high.

2)It helps to control and monitor the progress of work on your project.

3)No estimate can be as comprehensive as a qs estimate

4)Additional costs if there are any can be minimal

5)The estimate accommodates intangible costs/unexpected costs which can be as high as 10% of total cost of project.

6)It helps in control and gives room for you to question your contractor  based on what is stated on black and white when you suspect any foul play.

7)Specifications, quality and type of materials to use is clearly stated out unlike others.

The problem we have in this part of the world is lack of patience to find the substance in any information if  it didn’t conform with our expectations before throwing the entire information out.

A Qs estimates saves you money to any estimates you get from other building professionals like builder,architect,structural engr etc

These are the differences-

When a builder/architect/engr/contractor wants to give you an estimate, he will state the material to use quite alright and apportion the respective prices,  however none of these professionals will state anything about the quality of the material, but a qs will state the type, the maker, the country of production, the quality etc of the material you as the contractor is supposed to use, so there is no mistaking regarding the quality of the material to use and as you know a qs will always quote for the standard quality to use. For example as an architect I can quote for an estimate where I will state that I need to use twenty doors for a particular building at the rate of N45,000 per piece, now the issue is that I can have a door of N15,000 from China installed for you yet I can take you to a shop where you have doors sold for N45,000 and in same Lagos I can also take you to a place where a door is sold for N200,000, now imagine you knows nothing about the price of a door or you have no idea about building construction and you are far away abroad with a lot of cash to throw around. If I quote for a N200,000 door and you paid for it and you requested I take you to where they get such doors I will gladly do but the fact remains that since it wasn’t stated on my estimates where and the quality to buy, I may simply go for a N45,000 door. Now imagine what you’ve lost because there was no qs estimate to guide you.

Running away from qs estimate is foolishness, yes I agree it may discourage a prospective landlord but it can also help you to plan and sort for cheaper materials to substitute whatever is written on the estimate. For the above sample , if the qs had quoted for a N200,000 door and I quote for N45,000 door you won’t expect my estimate to be higher to the qs, now I can make money and work on your weakness because you are just after the lowest quote, I can raise the numbers or quantity of the material higher (for other unquantifiable materials) but of lower quality and simply pocket the money for the difference, since  you are looking for the cheap estimate but I can easily shortchanged you far worst than the guy that wants to buy a N200,000 door, of course you’ll always get what you paid for, you won’t expect the two doors to have same lifespan, would you?

Another one, if I am quoting for iron rod, I will only state the iron rods with the cost obviously the cost will be of the imported one which can be up to N30,000 difference per tonne to the local. However if the local can do the job and I am interested in making money I will simply buy the local despite that I quoted for the imported especially when you know nothing about this. But with a qs estimate it is hard because the yield strength of the iron rods will be stated which will affect the type and the price.

A qs estimate actually saves you cost because the quantity of materials difference can easily be questioned by you if the actual on site is becoming outrageously higher to what is on paper.

Omoonile, preliminaries and other estimates that will affect greatly the cost of your project will most likely be overlooked by any other professional.

The estimates generated by other professionals has a lot of ways usually related to their calling, for instance an architect estimate will contain more of finishes in the house, the frame of the building and others may be based on experience, a structural engineer  will most likely get only the iron rods or reinforcements accurate others will be more on experience. The builder will also concentrate on the frame of the building and costs of labour while others will also be based on experience.

For God’s sake a qs studied for 4-5 years the business of estimation in higher institution, he must have an edge over others.

Use the qs estimate get advice from him to help reduce the cost and he will know the best way to go about it.

The recent flooding around has brought new challenges and raised questions on wether to use iron rods to support the german floor of a bungallow, especially in a seemingly solid soil or not.
Going by what I saw inspecting a 4 bedroom bungalow close to the Ipaja canal in Lagos state has reinforced my belief for a careful analysis of any buildings prone to flood in future.
In this case on a particular Sunday when there was much rain, the water overflew it’s banks and entered people’s houses. For the house in question it was originally raised high which was constructed by me for over 5 years now and there has never been any issue of concern until this prolonged rain and blocked drains that led to unusual flood . The soil itself is sandy and fairly okay stability wise, other buildings are also standing around but to save money as most will do which is very wrong, we raise d the blocks straight from foundation up to the roof without breaking it with german/oversite concrete at the foundation/dpc level, we only pour some volume of concrete after the building have been roofed without any iron rods or wire mesh to really sustain the compressive force of the concrete.
Now a problem was discovered after the flood incidence, there were visible cracks along the walls both laterally and vertically, suggesting that the walls might cave in anytime, there was also serious movements of the ground floor concrete depressing further down and leaving a thin line between the walls and the concrete at the edges of each room round. These happened because the concrete were poured separately on each room just to sustain the weight of the occupiers and we didn’t put into cognizance the pressure a flood in the near future may cause. Ordinarily a German floor with wire mesh/reinforcements or iron rods casted together at the dpc (foundation) level will have given us a well formed monolithic mass of concrete that will have served as a protection against water penetrating directly from the ground to the house.
The water that surrounded the building went to its foundation ,soften the sands underground, and when the water dried the next day the soil under the building was further compressed by the wetness, hence there was movement of the concrete in the rooms which made them to go down and thereby separating blocks from the concrete.
This problem could have been avoided if the German floor was done and the concrete was made to pass on top and round the entire stretch of the building block, however without reinforcements on the concrete with the situation at hand despite that is a bungalow , we would still have had the same experience.
So I recommend for a waterlogged area, or for a site very close to the water or prone to future flooding, it is better to go the extra mile and reinforce the oversite or german concrete with iron rods so that if there is a movement under the buildingthe foundation and the german concrete will be able to sustain the building.
However if you have encountered this problem already, don’t fret yourself, get a professional to suggest the best way the building can be reinforced and also protected against flooding.

A prospective client first question is an estimate to know the numbers of blocks and number of bags of cement required  to complete his building project.

But for this article I will write on calculating the numbers of bags of cement for a simple project of 2 bedroom bungalow. Using the plan shown below.

For this plan the total wall both internal and external is 72.5m all (check for the calculations http://buildingcontractorsecrets.com/2010/09/how-to-calculate-numbers-of-blocks-from-a-building-plan/ )

Taking the thickness of block as 150mm or 6” the foundation base is taken as 150mm(or 0.15m x 3)=450mm or 0.45m or 18”.

Now for any concrete you want to calculate, first find out the volume.

For the foundation of the plan above

450mm(breadth) x 72.5m (entire length) x 150mm(foundation base thickness)=4.894m3

Now the volume of a bag of cement is given as 0.035m3 but lets use 0.03m3 to cater for shortages.

There are two major mixture ratio for concrete 1:2:4 or 1:3:6, there are others, but we are going to base our calculations on these two. 1:2:4 means one portion of cement is mixed with an equivalent volume or ratio of two of same portion of volume of cement in sharpsand and four of same portion of volume of cement in granite. That is, if I have a cement of 1m3, then I will need to mix it with 2m3 of sharpsand and 4m3 of granite stones. However one bag of cement is calculated to be approximately two headpans of sand or granite, therefore for one bag of cement in ratio 1:2:4, you will add four headpans of sharpsand, and eight headpans of granite, this is the standard , though experience has shown that materials properties varies, hence there is always little variations in quantities used on site.

Now, for the plan above, the numbers of bags of cement needed in the concrete is simply calculated by dividing the total volume of cement in concrete by a volume of one bag which is taken as 0.03.

For total volume of cement in ratio 1:2:4, add the numbers together,1+2+4=7

Divide the volume of concrete by 7 to get the volume of cement in concrete.

i.e 4.894/7=0.7m3 for volume of cement.

Remember  volume of one bag of cement is 0.03, then divide 0.7m3 by 0.03

=23 bags of cement

Also if the ratio is in 1:3:6, simply add 1+3+6=10

Divide volume of concrete by 10 to get the required volume of cement in concrete

i.e 4.894/10=0.4894 for volume of cement

Don’t forget we are taking the volume of one bag of cement as 0.03,

Then divide 0.4894m3 by 0.03m3

=16 bags of cement (this is most applicable on good and fairly stable soil.

I have been involved lately in projects that requires decorating with wallpaper. As simple as the job may look , installing it perfectly requires great care and professional handling.

Many corporate organizations in Nigeria now uses wallpapers to improve the ambience and promote their products. Recently  Mrbiggs restaurant and some banks are using wallpapers for their interior  decorations.

Advantages of Wallpapers

(1)You don’t need to paint your wall with expensive paints, just apply a primer under before pasting your paper.

(2)You can easily remove it and place another.

(3)It is dry and easy to handle especially when you understand the techniques.

(4)For a public building is a source of advertisement to your customers, you can write things, and send messages with your graphics on the paper.

(5)Drawings on plain wall seems not acceptable but with paperwall people have grown to like it.

To install, get your paper either printed or bought somewhere.

Clean your wall, this is important if you must get a good finish.

Remove every hanging nails, fill every holes with putty or cement and fix any other damage on your walls.

Now sandpaper to remove any rough patches before applying a coat of paint which is termed primer. It will help the wallpaper glue to the wall. The type of paint you use will depends on the type of glue to buy for the work, you can ask a professional for an idea on this based on the paint you used or ask the wallpaper  vendor for a clue.

Applying the wallpaper is where most people get it wrong, just like any other  projects it requires adequate planning on and off the wall before execution.

You must have measured the room horizontally round with a stretch of measuring tape with the  height  it will cover to get the surface area of paper you need.

Get a plywood to spread the wallpaper on it before pasting on wall.

Notice the areas you have to join the wallpapers on the wall, this is where you have to use technical knowhow , make the papers overlap slightly right on the floor when you are mapping them  out. At the intersection , cut the overlap portions at the middle so that the blade will follow same line of paper ontop and the one under, when you remove the pieces slide the two papers and let them join at the points the blade passed, you’ll discover a perfect fix at that junction and if its carefully laid an outsider will not detect  where the papers are joined together . Infact a well finished wallpaper job may confused an outsider to be a painting or drawings on the wall.

Wear a latex glove or rubber to keep the glue off your hands, also get a roller, clean up the surface of the plywood, apply glue on the wallpaper which has been properly cut, then paste on wall, you can adjust before the glue dries up. Place the next one after  (remember to overlap adjoining paper on the ground and cut at the middle, remove the pieces to be left with perfect fitting edges)

Cut any extra sheets carefully with blade and do not cut the papers at any junctions of the wall but at centers of plane surface, just allow the paper to continuously wrap round at the 90 degrees edges.

Use a smoothing tool or a clean roller and roll from the middle of your paper out to the edges to push out any air that would make bubbles.

After installations, clean up the wallpaper with a wet sponge to get rid of any glue that remains behind and also to press down any lumps,bumps and bubbles out of the wallpaper.

HOW TO TAKE LEVEL

The builder is expected to carry his levelling instrument to site with an assistance along with
him to do the job. A reference point is taken in the building and is marked out, then measure
the height you wish to achieve from that point up. Now transfer the level or point to the four
corners of the building, when this is established, the carpenter will only need to throw one
line from one place to the other and he can begin to place the planks along the line. Some artesans will tell you that they can use plumb to get this level, this is not true, the best method is to use the levelling instrument. Measuring same distance directly from the ground floor to the top and doing same all over the building especially when its not a precast
structure, shows technical deficiency on the part of your builder, because most floor slabs are
not on same plane out of errors due to settling,lack of technical knowhow and carelessness from
the casters of the ground floor slab.

After the level is determined by the builder, next is for the carpenter to get ‘water level’ he will use this to transfer the level round the building. Water levelling instrument is an ordinary hollow transparent cylindrical rubber pipe that is filled with water and is easy to turn around the walls of the building. Remember water finds its level, the level of water at the end of the pipe in one place will be the same level at the other end of the pipe, so is easy for you
to transfer and determine the level round the building.  After placing the planks supported by bamboo or iron rods under with other wooden materials like 2″ x 3″ wood, the iron bender is called to start fixing the iron rods on top.He must have prepared ‘concrete biscuit’ which is used to raise the iron rods to avoid contact with the wood, if not, by the time the plank is removed some parts of the iron rods will be exposed to air or moisture which will cause rusting and ultimately decay.The iron rods for the floor slab is run along, and the electrician is also expected to fix his pipes and sockets, likewise the plumber will also do some work if need be before you call the casters in to cast the concrete for you.

WHEN AND HOW TO CAST CONCRETE

Be prepared to rent a concrete mixer and labour for the casting especially when the area of
concrete is much. Mostly the concrete is in ratio 1:2:3 or 1:2:4 i.e one bag of cement to four headpans of sand,
and eight headpans of granite.Except for peculiar sites this ratio is ideal.

Inform the caster to bring a vibrating machine along, this is used when casting so that the concrete will settle properly and  there will be less holes in the concrete.If you can get granites of smaller sizes like half inch to do the beams, it will  be good for compactibility. The concrete will form well with finer smaller stones aggregates.As the concrete is been poured, follow the casters behind closely with vibrating machine and work on the concrete. make sure the beams are well vibrated at the joints especially because of the clusters of iron rods if not the concrete will not cover the beam properly.

Get a good mason that will spread the concrete round evenly with range and plumb for best result.Next day pour water on the concrete and blockwork can start on top that same day. By 21 days or three weeks the bamboo or cylindrical iron pipes support under can be removed, it must have fully set. Remove any cantilevered side after 4 weeks or a month.

(1)Find out about the most recent previous sale of the house information-Knowing the year the building was sold and if it had been passed from one buyer to the other and the cost will go along way to determine how much you will pay considering the number of years, when it is overpriced you can use the previous cost to beat down the price.

(2) Purchasing abilities of people at the time-Due to global eonomic meltdown, few people are actually buying houses, hence there are lots of buildings in the market without buyers,when you have such situations just as it is at the time of writing this article, then the cost must go down and you can use the lull in the real estate market to your advantage by also pricing lower.

(3)Check if the right taxes are paid on the house where applicable, if you notice default then you can also put this forward during negotiations.

(4)Relative costs-Check the cost of other buildings in same neighbourhoo, this will give you an idea when the property you are about to price is overpriced.

(5)How accessible is the building to other parts of town

(6)Can you enjoy good basic infrastructures.

(7) Get a valuation report or an appraisal from the real estate agent

(8)Check when last the building was renovated, you can also use this to negotiate.

(9)The rate of population growth is also important in negotiation. It can affect the pricing negatively or positively, so take advantage of it.

(10) Is the area prone to flood, may be the house is at the lowest part in that area

(11)How good is the road leading to the building?

(12)Factor in other basic infrastructures not in place

(13)Check if the building is in an unplanned or unorganized neighbourhood.

(14)Take a contractor to the site let him give you an estimate of the cost of repairs on the house, use that to negotiate the price of the house by removing the cost of repairs

(15)Check for NEPA/PHCN, water and other outstanding bills that were owed by previous occupier. Though small and almost insignificant but it helps in the psychological war of reducing the price.

(16)What economic value does having a building in such area have? Is the place going to develop very fast from your accessment, does it have the potential for revenue generation in the nearest future. The economic value of a house will either reduce or increase its price too.

(17)Is the area an exclusive neighbourhood? or is a rowdy place with area boys or social miscreants everywhere.

(18)Finally call a building professional to the building for assesment and to give you the best advice on the house.