Badgers14:


Is there a limit to using this precast slab?

Like can one use it in multi storey buildings like say 3 to 4 storey?

I have seen this trend in east African buildings but they are usually one storey building.

Yes, it can be used for multi storey floors.

It's a matter of structural design, the frame is designed to resist the lateral loads while the slabs can be rib slab and this type of block can be used.

nedu666:
Indians plenty for Nigeria, more will come make money, employ indians as head with big pay and Nigerians as tail with slave wage. At the end, they will repatriate their money to Swiss Banks

Most of the time, over 70% of the money remains in the country!

DaddyFreeze2020:


I hope he knows the Hausas who make up the majority of the Nigerian Army rank and file will not willingly fight Niger Republic. They will sabotage his efforts.

The Hausas don't make up the majority of the rank and file, more like the minority group from the middle belt.

Stop projecting your phobia for the Hausa-Fulani people over everyone.

CodeTemplar:
Lol... N200/kwhr rate loading. By the time they do those their wuruwuru PPP and inflate cost, Lagosians will be lucky to get N200/unit.

If you are conversant with how power sector work you will not be saying this rubbish.

Power will be deregulated and gov't will stop fixing the price for it to work.

When you run your generator and you buy your fuel to do so, how much do you think you spend to do 1kw/hr? Way more than N300....

Here, Polystyrene was used as the concrete fascia and we have some light in it. It looks good trust me.

More on our Surulere Project

Truthisunique2:
Makinde want us to believe Yoruba should support Yoruba candidate irrespective of difference

But they believe north shouldn't support their own son too

makinde is 50/50 on his return as governor, trading assurance with Tinubu is a win for him

He is on the same camp as wike the basketmouth who is pro Tinubu

Do the maths

Yes, northern votes is very enough to makr Atiku president, he is the only one that can do averagely below average in the south to balance all he needs from north

North is not a tribe. Atiku belongs to a minority tribe from a state outside the northwest. An ethnic card wouldn't get him elected.

Religious sentiment is stronger than ethnic consideration in the north. I would say, Atiku is not going to get the sentiment of the majority of the people in the north �.

You guys can continue to fool yourself out of the hate you have for Bola Ahmed Tinubu but it wouldn't stop his emergence.

b2212:
looks similar to the clay decking pot technique.

It's the same principle, except that this one has its rib precast.

Here is one rib slab that I constructed in the Surulere area last year. We saved some money by adopting the method.

Gigaset:
This method are common in most African countries I don't know why we don't use this method here in Nigeria,in Kenya they use this method is called Beam & Blocks think of how much someone can save on formwork,steel bars, bamboos etc using this method

This is precast rib slab construction. I'm planning to start providing this service in Nigeria

It has lots of advantages like, it being cheaper, it's faster and it's as sound as the rigid slab normally adopted in Nigeria.

Also, you can achieve the required strength for the rib beams because they can be properly cured.

One major disadvantage is that its joints need to be properly designed especially for areas prone to seismic activities.

I hope you guys will patronize my smart_slab solution �

KolaShangOne:
What do you think of this strip and pad + slab beam raft foundation..

Load bearing differs on the same plot..

Cc @abdulwastecx @aforxzy @timtol @primequay

And others.. pls feel free to critique.

Oga kola, I'll like to see more pictures and details before I can commend appropriately. Things like;
1. How many floors you are trying to build
2. Bearing capacity of the soil. Amongst other things.

Generally, this combination is good for soils with a tendency for serious differential settlement.

But note, this combination is strip, pad footings, and ground beams. But it looks solid sha Oga.

joedguy:
Pls my oga,can sand gravel be used for casting foundation and lintel. Thanks for ur response

Do you have a picture of the same gravel?

What is the size of the building that you want to work on?

Aventures:
Hello everyone, Las las @ Akinola88 Vs Rotech77 (or we say 88vs77) has been partially solved so to say and this thread can return to learning status.

Can we kindly share lessons learnt from this event ranging from moral, technicality and finance

Lesson learnt by me

1. Lowest qoute is not always the best atimes. Client should engage cost expert such as QS, project manager for cost analysis to determine the best qoute that will help in smooth project delivery

2. Engineers/contractors should not be greedy by intentionally luring client to give you Job by qouting low, with the intention of coming back to plead for more fund or delivering poor structure.

3. A third eye as Quality control and Assurance can be engaged to avoid stories that touch after some few years of delivery, note that houses are built to last for at least 70 years, even at 70yrs the house can still live longer far beyond with minimal retrofitting.

4. Liking or falling for beautiful pictures is not enough for contractors selection, get references from both online and offline of your choice contractor, physical visit to ongoing and past projects as well is a plus. Choose wisely.

5. Tiling parapet wall of a flat roof is not the best solution, rathe cladding with aluminum flat sheet is the best. Tilers or masons don't know how to walk on roof so obviously they would do damage to the roof, meanwhile the cement and aluminum sheet don't bond, it is a matter of one season leakages is inevitable.

Kindly add yours and @77 and @88 can as well share their personal lesson learnt.

Thank you all.

All these are excellent points coming from years of Engineering and construction experience.

1. I would say, surely that QS should do the take-off and allow the contractors to put the rate. A mechanism can be put in place to verify that the items are delivered based on the specifications. For example, Concrete grade can be verified by cube tests, block strengths, steel strength,
etc can be very by material testing.

2. I think there is no way to solve this problem of contractor greed. Also, I've observed that people-trained engineers are more aware of the actions of cutting corners and not really building according to building codes. I'm not saying this because I'm an engineer or biased towards the civil/structural engineering profession. Also, I'll advise that when you can't hire a civil/structural engineer to build your structural frames/Carcass for any building over a bungalow you should hire them as a consultant.

3. Quality control is one of the most important parts of construction. For example, the difference between M15 and M25 can be a lack of monitoring and poor quality control. too much water in like half a bucket can weaken concrete by more than 50%. A lack of vibration may render it very weak that which will allow the rebar to corrode etc. I would put that durability is as important as the strength of the concrete. Quality control requires that you have an expert on-site to make sure that materials meet specifications and that construction is done based on guidelines.

KolaShangOne:


Oga Abdul, your 1,2.5,3.5 gives you M25 grade concrete.. That's 1 cement to 5 sand to 7 aggregates.. Do you use additives? Or could it be the 42.5R cement? Or the size of the aggregates?

I know it's 1.1.2. that's guaranteed to give M25..

I use 1,3,4.5 for my bungalows.. I get up to 18 -20N/mm² after 28days..

The magic here is grading, limiting the water-to-cement ratio to 0.5, proper curing and proper vibration.

If these variables can be controlled properly I think, 1:3.5:4.5 can easily be achieved.

I've been using this mix design for some time now and whenever I carry out a test on the cured concrete I always get over 25N/mm2
I think I will have time soon to discussed and shared some of my findings soon.

Finishing the external plastering

Akerewe:


Good day engineer, pls if am not wrong ur 1:2:5:3:5 means, 1 bucket of water, 1bag of cement, 10 headpans of sharp sand, 6 headpans of soft sand, 10 headpans of Granite
Pls correct me if am wrong!
Also how many litres of water is ur 1 bucket equivalent?

I think 1 bucket is 25liters.

It's one bucket of water to one bag of cement.
Let me use this simple calculation to buttress the point.
assuming that you want to use a Water/cement ratio of 0.5. Hence for 50kg of cement, you will need 25kg of water.
Since the density of water is 1000kg/m3, and mass = density x volume.
since one bucket is 25litres = 25/1000 m3
mass = 25/1000 x 1000 = 25kg.
hence 25litres of water is 25kg.

Also to the final question that you asked,
1:2.5:3.5 mean
for every bag of cement ( which is 2 head-pan (flat)
5 head-pan of sand ( flat the surface, don't hip it)
7 head-pan of gravel (flat the surface don't hip it)

The building is now coming out so nicely. The plastering is taking shape. Let me quickly throw in some technicality here.

For this plastering the ration for the mix is 1:5 (that is one part of cement to eight part plaster and two part sharp sand)

There are some chiselling and filling that we need to do because the walls are not both horizontally and vertically straight.
We are up for the task, remember we are not the contractor responsible for the carcass. It's expected.

We are building some ducts too. My experience with plumbing in Nigeria is to always create a duct for all your planning, especially for a commercial buildings like this one

We need to get the gable and plastering done too!

The roofing

Lintel, columns, head beams, and gable work

Scope of work;
1. Complete the blockwork
2. Lintels, columns, and head beams.
3. Construction of 6 different ducts for the plumbing work
4. Roofing work
6. Fibre cement board plastering.
7. External plastering.

Duration of work 1 month.

We are roofing, addressing some of the structural works, and external plastering to this house at Elebu Ibadan.

Ibadan, Ilu oluyole, here we are.

Slimszy:
Hi guys, I am currently facing an issue of water damp in my building. It's so frustrating.

I have broken the plaster about 2 feet above the ground in the interior, and it has risen to the upper part within 2 months, causing the screeded wall to peel off. I am completely tired of maintaining and maintaining a new house.

I need your advice please.

Dampness is a big problem with most Nigerian homes.

The primary case of dampness in buildings is capillary action. This is a phenomenon where water around the wall areas rises through the wall through this action.

The primary way to prevent this is to institute a dampness program during construction. If the site has a high water table, properly drain the foundation, use moisture barriers on all walls, and create a damp-proof membrane on the ground floor before the oversite concretes and provide a french drain to take accumulated rainwater from the building perimeters.

For this case, you will need to constantly remove water from the building perimeter using a french drain. Then peel the plastering up to around a meter high from the foot of the building, and replaster this portion of the building with a cement-riched plaster (1:4, one bag of cement with 6 parts plaster sand and 2 parts sand) also add a water sealant cement to the mix. If you can also paint the external wall with water sealant paint it will also help

olukaygold:

I hope you know the meaning of 1:2:4??
If this is true, You're a Big Man Woman ooo

But 1:2:4 will not even give you the minimum required strength for most reinforced concrete applications.

If most reinforced concrete work. I use 1:2.5:3.5 which will give characteristics of concrete compressive strength of 25N/mm2 after 28days.

Also, the water-to-cement ratio is so important. W/C of 0.5 which will translate into 1 bucket for one bag mix should be the way to go.

For example, if Mr. A uses a mix of 1:1.5:3 with too much water, 1.5buckets, and Mr. B uses a mix of 1:2.5:3.5 mixed with 1 bucket, the strength achieved by Mr. B will be better than that of Mr. A with all things equal.

In summary, quality control is as important as the volume of cement used in concrete production. Also, I experiment with mixes and carry out tests from time to time.

famouscargo4u:


It was population explosion that changed the whole thing. Lagos' population was less than 4 million then

Lagos was around 1.5m in 1960; even in 1980, Lagos had less than 4m people.

LoveNbeloved:
So can we do Christian-Christian ticket?

Awolowo run on Christian-Christian candidate. Infact, it was a Southern - southern candidate and he came close to wining in 1979.

Azikwe run on Christian -Christian candidate too in 1979

A cantilever on both sides of the beam which is called an over-hanged beam can be made to be beneficial to the beam and to reduce the moment induce on the column. This is done by having an over-hanged of 1.2m on both sides to achieve an optimal design.
Also, we have also decided to use a rib slab here to reduce the slab dead load and save some cost due to the high cost of cement.

Let me take a moment to talk about the rib slab used for this project
A clay block of 400 long, 250mm wide and 200mm deep was use
With a topping depth of 50mm
The width of the rib beam is 125mm
height of rib beam is 250mm

We completed the ground floor pretty quickly and we move into the ground floor formwork.
Here we'll show you guys some of the 1.2m cantilever we introduced on the ground floor to add more floor area to the building

As you guys can see from the last picture. After the casting of the ground floor columns, we build up the blocks. More pictures from the ground floor blocks

We'll be casting the ground floor columns before the laying of blocks. These ground floor columns are 300mm x 230mm and reinforced with 4Y16mm with 10mm rings spaced @ 200mm. The building frame was arranged in such a way that the maximum distance between any two columns was limited to 3.8m. This was done to reduce the concentrated load's transferred to the foundation and the reinforcement of columns and beams

Raft foundation transfer loads to the soil below through the help of the slab. Hence the slabs are designed as an inverted floor slab ( that is, instead of the load acting downward, the soil pressure will exert an upward force on the raft-slab

This particular raft-slab is 200mm thick, reinforced with the span reinforcement on top @ 200mm centre to centre with 12mm and the support reinforcement placed at the bottom, in areas where the beams are located, reinforced with 12mm @ 250mm centre to centre