here are some of our ongoing construction work at different locations within Nigeria

Project #1.
four units of one-bedrooms, two-bedrooms and two units of three-bedroom flats on a single two suspended floors building.
client:
contractors/consultant: weBuild (abdulwastecx)
Location: surulere
type of foundation: raft

after a detailed soil analysis was carried out, the geotechnical engineer recommended a raft foundation for the building.

The raft was 1.2m deep with a raft slab of 250mm deep.

The building is on a site of a demolished building.

We have to excavate to 500mm, blind for 100mm before setting up a beam of 1200mm.

Why do we need to excavate?
Excavation is required to prevent the building from overturning due to wind uplift. Since the building needs to be anchored into the ground .
For this project, we'll be using 3Y16 top and bottom and 4Y12 both side of the beam.

The 4y12 is provided on both side to prevent cracking in other to meet up with the rules of detailing in accordance to BS codes.

Before I forget, the filling and compaction took us almost three weeks. Simply because we have to compact in layers of 150mm to achieve adequate compaction.

The question is why is compaction so important for this type of foundation ( raft slab built on fill)?
It's important because the fill will receive and carry the weight of the whole structure. Though, the beam will help to prevent shearing at column points.

I think, this is the common mistake or misconception with this type of foundation. It's wrongly believe that as long as the raft beam is well done and reinforced, that the slab can be reinforced with wire mesh or lightly.
This is wrong. Slab in a raft construction are design like that of solid or flat slab and the reinforcement is opposite to that of the suspended slab (i.e, span reinforcement ontop and support reinforcement at the bottom)

Glad to see a new project construction from you again. Good work always.

Hajji M.

mufutau55:
Glad to see a new project construction from you again. Good work always.

Hajji M.

Thank you sir and thanks for all the good recommendation sir.

These are the questions that lots of people do ask about the Raft foundation.
What is a raft foundation?
How does the raft foundation transfer the building loads to the soil below?
What are the components of a raft foundation?
How do we size these raft foundation components?
Why do we even use raft for foundation work instead of the strip, reinforced strip, pad and even pile footings?

These and more will be answered as practical as possible as you follow us on the journey to deliver this beautiful building.

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

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

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 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

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

Ibadan, Ilu oluyole, here we are.

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.

Lintel, columns, head beams, and gable work

The roofing

We need to get the gable and plastering done too!

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

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.

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)

Finishing the external plastering

More on our Surulere Project

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