BuildingContractorSecrets.com

Basic measurements and conversions of feet and inches to metric and plots of land

emma — Wed, 07 Dec 2011 00:50:51 +0000

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 450m²plot

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

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

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The Differences Between the Qs estimate and others

emma — Thu, 22 Sep 2011 14:12:01 +0000

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.

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When to use Iron rods in the oversite/german floor concrete of a bungallow.

emma — Mon, 22 Aug 2011 00:28:48 +0000

Mr. Emma

Please find attached a quotation for foundation sent to me by a contractor. i have excavated the land and some part you will see that its water logged. a lake is behind my land at igbogbo ikorodu.

Another contactor said i do not need iron rod for foundation since its a bungalow?

Please advise.

Regards,

Chris

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.

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How to calculate the numbers of bags of cement in the foundation of a simple bungallow from a building plan.

emma — Sun, 03 Jul 2011 22:51:41 +0000

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.

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Decorating and Installing wallpapers

emma — Sat, 14 May 2011 23:42:17 +0000

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.

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Post tags: alternative to paints, decorative, interior, wall paper

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How and what to do when preparing for your decking/suspended floorslab

emma — Sun, 05 Dec 2010 23:52:57 +0000

For a building that must have more than one floor, you need to factor in the technicalities involved when putting in place the concrete slab. For most of the poorly done projects, decking or suspended slab contributes majorly to the cause. Knowing what to do is more important than been present 24 hours on site to achieve nothing.

These are the basic steps to follow…Get your architect or engineers to calculate the number of planks and other wooden materials you need for the decking, the number of reinforcements or iron rods, the volume of sharpsand, granite and numbers of bags of cement required.After getting these calculations right,call your electrician and plumber to site for the estimates so that they can place their pipes before the concrete is formed. They may need to break some blockwalls even cut iron rods in extreme cases for the pipes to fit in.After getting the materials to site,invite the carpenter to start placing planks for beams that will transfer loads from the concrete decking to the foundation through the columns/pillars in the building.But before you give the carpenter go ahead, make sure you call a builder to site to give the right level for the decking if not, you will have very uneven decking especially when the soil is weak and buildings settles very fast on it.

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.

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How to technically reduce the cost of buying a House

emma — Sun, 14 Nov 2010 23:03:30 +0000

Getting places to build especially in urban area is increasingly difficult, hence most opt for the outskirt. But if you must build in an area that is completely built up, you will have to buy a house which you must demolish to build your own or renovate.There are basic tactics you can use on the seller to price down the cost, but you have to make sure you don’t get him or her offended.

(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.

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Post tags: buy, house, house cost, sell house

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Who should handle or supervise your project? Architect,builder civil or structural engineer

emma — Mon, 25 Oct 2010 23:14:35 +0000

There is always a confusion in choosing who to handle or supervise a project especially for a newbie property developer.

Questions have been raised severally on who should handle individual projects, however building types will determine who you should use as an arrowhead onsite.

The larger your project, the more the numbers of professionals and technical people you are expected to have on your building site.

For smaller projects like 2 bedroom bungallow any of these professionals are okay for it, there is no need to have more than one professional on site for small projects.

A young architect, builder or structural/civil engineeer can on their own supervise any bungallow with little or no supervision. But when it is a storey building especially a multistorey building or duplex, then you need the input of the architect not only as the designer but also on site as the overall

supervisory officer, in some cases they may supervise on secondary role basis.

The builder is trained to execute every line of command represented on sheets of paper by the other building professionals, therefore a builder is more at home on a building site more than any other professionals, because that is his major occupation. He can enter the roughest parts of site and see to it that job is done properly and he likes to be physically involves most time.

An architect has very strong ability to detect an error, he is trained to be a perrennial critic, he sees the building as his baby and ready to protect the baby jealously, the pride of an architect is to see his design come out well executed and beautiful.

Now take the architect as the mother of the child (the building), the builder as the nanny. The nanny does all the dirty works, work hardest and may be closer to the baby than the mother. But the mother happens to be the one that conceived and bore the child, so she is more protective of

the child, she has a vision of how the baby should look like in the process of growing, she monitors her and anything shot of her expectations will not be welcomed. she may have to shout at the nanny when the baby is not well fed or taken care of.

The architect surely did the work of conceiving and drawing plan of the building, but he may not neccessarily have much physical impact but technical in actual construction, but he knows exactly how the building should look like and what he wants, so he won’t settle for less.

The structural engineers job concerns the stability of the building, so we may take the structural or civil engineer as the peadiatric doctor that monitors the health of the baby and prescribed drugs to sustain his or her life. This is also the function of a structural engineer to the building. Architects likes to fantasize and come up with out of the world designs, it takes the engineer to look at the design and relate with the architect about the structural disposition of the building, if its possible to build with the technology and expertise available or not.

An Engineer makes sure the building is healthy by prescribing the right reinforcements/iron rods to stabilise the building and stop it from eventual collapse.

From the illustrations above it is important to have at least two of the major three building professionals mentioned above on your site especially when your building is a storey building or more complex structure, afterall two heads are better than one.

The structural engineer and the architect could take a supervisory role whereby they come to site to make sure their designs are followed strictly and give them opportunities to pass down further instructions and incase of adjustments or redesign, they will be in best position to know what to do.

Whatever case, one of them should be on site preferrably a builder.

For higher storeys and more complex structures, the architect,the building engineer/builder, the structural/civil engineer, the electrical engineer and the mechanical engineer are suppose to be on site. (the mechanical engineer deals with the plumbing works).

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Post tags: architect, builder, civil engineer, developer, plan, structural eengineer, supervise

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Preparing for plastering and how to avoid plaster cracks

emma — Fri, 24 Sep 2010 22:55:34 +0000

Plastering is the most important part of the finishing job in a building project, whatever error

made during plastering may be difficult to correct,because after it, is just to paint and fix

other accessories.

Plastering takes a lot of cement and is important the mix ratio quality is not reduced because

of the consequences.

Care should be taken right from the type of sand you ordered, bricklayers prefer the sticky ones

because they bond easily without applying too much power to splash the mortar on walls (though

this does not automatically means is the best to use.)

The sand must be clean, should not have dirts, and any sand with dirts should be sieved.

As said adequate numbers of cement with standard cement and sand ratio should be maintained.

Is also important you get good hands to do the jobs for you.

Plaster cracks leading to an opening a door.

To get a good plastering job, tell the masons to apply guage. Guage is just a term used by

masons/bricklayers which is using a thin material especially wood with rope to mark out how the

plastering will spread round the surface of wall of the building to achieve perfectly vertical

walls. Blockworks are usually not done to perfection especially when the bricklayers are not

very good, often time, the blocks will not stand perfectly vertical, therefore some areas will

require more mortar filling to others to compensate for the bad areas, so guaging is what you do

to achieve a perfect plain. In doing this some areas will require more mortars than the others.

Plastering is usually applied between 15mm to 25mm, but some areas may require more mortar, in

such cases, apply cement and sand, leave to dry till the next day before you apply the finished

coating for a smooth surface. Leave the area you filled till the next day and allow to dry

before you apply the final coat on it.

I prefer a mixture ratio of 1:5-1:6 for cement, sand mix.

Causes of plaster cracks

Plaster cracks as a result of electrical works

(1) Deep filling not allowed to dry properly-Don’t give plastering project to your

masons/bricklayers on per day payment because when you pay for the job done per day, a mason

must finish up the portion giving to him before the day runs out, so he will fill and won’t wait

for it to get dried before applying the final coat. The plaster filling requires minimum of 6

hours to get dried, but a mason that is expected to be paid on daily basis will not have the

luxury to leave such portion till the next day so that he can take home his pay, hence the

plaster will be applied before the filling get dried, this will inevitably cause cracks. The

plaster filling will shrink and contract in the process of drying, this will cause it to leave

strips of cracks inside which will allow air to fill the space and inevitably will also affect the plaster

finish on top.

(2)Bad plaster sand-The sand is supposed to be fine with no impurities and should be able to bond

well with the cement.

(3)Shortage of cement-When the cement is not adequate, the plaster will not bond well and will

results in cracks.

(4)Pipe holes left by plumbers and electrician-The pipe holes where pipes are placed in should

not be covered immediatelywith plaster, because of the space, the holes are better not left to

the plumbers and electrician but there should be a mason/bricklayer on site that will be

responsible for filling back the holes. First fill the gaping holes with broken blocks, then

apply plaster, leave to dry till next day or more before final coating to finish.

(5)Poor workmanship-Get a good bricklayer/mason for this project.

(6)Dirts and impurities in plaster sand will also affect the outcome of your plastering.

When you notice a minor crack, apply cement slurry by that I mean mix pure cement with water,

then use brush to run the cement along the lines of the plaster.

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How to calculate numbers of blocks from a building plan.

emma — Thu, 09 Sep 2010 01:56:19 +0000

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Most asked question from a would be house owner is always how many blocks do I need to get my building completed. Hence this topic is written with illustrations to make it easy for you to do

the calculations yourself from the plan your architect gave you.

The plan above is for a 2 bedroom bungallow, so we are going to start from the basics having in

mind these factors-

i)The lenght of a block is 0.45m or 450mm or 18″

ii)The width of thickness varies -150mm or 6″ and 225mm or 9″ which are most common.

ii)Taking for a general or average purpose, the blocks laid from foundation to dpc(german or

oversite concrete) is 4 coaches/levels. From dpc to the base of window another 4 coaches,from

base of window to top of window another 5 coaches, then from top of window to base of roof

another 3 coaches, neglecting the lintel or concrete on top of window.

Now with these parameters let calculate the plan above which has a wall of 150mm or 6″ all

through.

Add the length and breadth of the blockwall for external and internal

Therefore (A)9,400mm +9,600mm(B)+9400(C)+9600(D)=38,000mm or 38m

Now add the internal walls too

(Follow the grid lines and check the corresponding dimensions on plan remember 150mm is the

block width)

(Grid 7)150+3600+150+150+3600+150=7,800mm or 7.8m

(Grid 6)1350+150+2250+150+825+675+150=5,550mm or 5.55m

(Grid 1b)800+2400+1300+900+100=5,500mm or 5.5m

(Grid 2)2600+900+100+150+100+900+500+150=5,400mm or 5.4m

(Grid 3)1800+150+650+900+250+900+1450=6,100mm or 6.1m

(Grid 3b-Kitchen)900+50+1200+50+150=2,350 or 2.35m

(Grid 7b toilet)1800 or 1.8m

Total internal walls=34,500mm or 34.5m

Therefore Total walls=38,000mm +34,500mm=72,500mm or 72.5m

Now for the first 4 coaches to dpc level the wall will run right through, i.e the spaces for

doors or windows are not left out (n/b- blocks are used in relatively strong and stable soil not

waterlogged area that requires concrete instead).

Divide the sum by 450mm to know the numbers needed for one level/layer/coach of blocks

72,500/450=161 blocks

From dpc level to roof lets take the numbers of coaches to be 4+5+3=12 coaches

then multiply the numbers of blocks for each coach above by 12

161 x 12=1932 blocks

Don’t forget we have windows and doors spaces which we need to remove,for each window of 1200mm

take numbers of the block to be 14 (i.e 1200/230=5.2 and 1200/450=2.6 ,5.3 x2.6=14 approx

Now count the numbers of 1200mm windows and multiply by 14

Total numbers of 1200mm windows as counted on plan is 12 (note 2400mm window was taken as two of

1200mm window)

i.e 11 x 14 =154 blocks + 7 blocks for 600mm window for toilet. Total=161 blocks

Now calculate for doors,Numbers of blocks for a door of 900mm is 18.

height of a door(2100/225=9)+width of a door (900mm/450mm=2). so 9 x2 =18 blocks for each door.

Multiply 18 by numbers of doors=18 x8=144 blocks

Add 144+161=305 blocks,then remove from total blocks of 644 (for dpc) + 1932

Total numbers of blocks reqd=2,271 blocks

For a quick calculation, having the entire length to be 72,500mm. Take for a bungallow total

lenght from foundation to roof to be 1,200mm +3000mm=4200mm

Then calculate the surface area which is 72,500 x 4200 and convert to meters

72.5m x 4.2m=304.5m2

Remove surface areas of windows and doors

For window, height is 1.2m and total is 11

i.e 1.2m x 1.2m x 11=15.84m2 +0.6 x0.6(toilet window)=16.2m2

For doors, height is 2.1m while width is 0.9m

i.e 0.9 x 2.1 x 8(nos of doors)=15.12

Total area for doors and windows=16.2m2 +15.12m2=31.32m2

Remove 31.32m2 from 304.5m2=273.18m2

Now divide this by surface area of a block which is 0.225 x 0.45=0.10125

The blocks reqd caculated by this method is 273.18m2/0.10125=2,698 blocks

Note a difference of about 400 blocks from the two calculations. Of course you can’t get exactly

the numbers you need but the first method is close to it. And calculations are not 100% true

because of these factors

1-The mortar space was not considered

2-Blocks that will be wasted due to breakages e.t.c

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Post tags: 2 bedroom bungalow, blocks, bricks, calculate numbers of blocks, dpc, estimate

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