₦airaland Forum

Empiree:
what type of roofing sheet used with polystyrene fascia in this house?

Besides, which of this fits better on polystyrene fascia:

Metcoppo ?
Stone coated step tiles?

Stone Coated tiles is better because it is more fashionable and people like it but is much expensive.

Metcoppo will also do a good job

Empiree:
Do me a favor please, I am aware of polystyrene fascia being costly but very light. In reference to this property you are currently heavily renovating, how many sqt/sqm is it or how much it costs (excluding installation) to buy polystyrene alone for this house (total)?

I just want to have idea, that's all.

We don't measure polystyrene fascia in square meters, it is measured in linear meter (perimeter). The total perimeter was 120m @ about N4,000/m = N480,000 (excluding Transportation).

The polystyrene fascia is not very costly when you compare it to in-situ cast fascia, though it may be more expensive than pre cast but not by much

mavverick:
Is this the way forward, and I wonder how much it will cost for a 60 x 120 standard plot. Using this short bored pile vs 2 board raft all the way around.



EFFICIENT TO USE SHORT BORED PILES FOR PERIMETER FENCING IN SWAMPY AREAS?


It makes more economic sense to use short bored piles for perimeter fencing in swampy areas than to use raft or deep strip foundation which is in common use, it has been observed. However it is important to do it the right way. Generally, perimeter fence consists of non-load bearing walls or partially load-bearing walls depending on its use and configuration; hence the use of short bored piles is structurally permissible. By constructing reinforced concrete piles with adequate spacing, usually not more than 6m apart and capping them together longitudinally, fence walls of up to 4m can be built directly over the cap (or longitudinal bearing) saving the volume of concrete by up to 50%. Apart from being economical to use short bored piles capped together, it is equally structurally efficient.

Short bored piles are so called because they are constructed by boring the ground and then filling with reinforced concrete or mass concrete and they normally do not exceed 5-metres in depth. They are relatively easier and quicker to construct unlike the longer ones. Once the depth of suitable soil strata is established, rather than constructing raft or strip which consumes cost associated with trench excavation, formwork consisting of several boards lapped together with a lot of bracing as well as heavy reinforcement accompanying the concrete in foundation which is the common practice, it is faster and cheaper to use short bored piles.

Once the fencing layer is filled, prepared and the boring points are marked, the boring is done simultaneously with the insertion of the reinforcing steel piles (usually no casing is required) and concrete in an operation that may not usually do not last more than 30 minutes per point depending on the nature of the soil beneath. When the piles are set, a network of steel reinforcement is used to cap the starter bars of all the piles together. Te set up is casted in concrete and is now set to receive the blocks or bricks for the fence. Presently, it cost an average of 10,000 NGN (depending on the area) to bore and fill a point. Hence for a 36m length which could be one face of a standard plot, only about 7 points is required and the volume of concrete is therefore minimal. With the cost per cubic metre of concrete still hovering around 30,000 NGN, it is more than logical to conclude that short bored pile foundation for perimeter fencing in swampy or water-logged areas is the way to go especially for large areas like residential estates, industrial complexes, etc.

Culled from Castles Magazine.
Article by Engr. Osaz ENOBAKHARE

There is already a misconception about raft foundation here. Raft foundation don't support line load/wall land, such type of foundation is called beam on grade foundation. This grade on beam foundation is a continuous reinforced concrete members use to support load with minimal bending ( wall loads).

This beam on grade foundation can either be supported by soil beneath if the soil have adequate properties or pilliing in areas with poor soil ( water lodged soil).

Responding to this article, it is more expensive to construct pile foundation or more appropriately '' pier and beam foundation or post and beam foundation) than reinforced wide strip footing or ordinary beam on grade foundation because you will need this pier to be spaced closer to each other and you will need to connect them with grade beam of adequate depth and reinforcement. in practice, this method is an advanced form of beam on grade foundation.

The choice of any of these type of foundation depends on the type of structure and soil conditions. In expansive soil where there is a distinct wet season ( the soil behave like water lodged) or dry season when the soil is normal, a wide strip can be use to carry a fence wall of up to 4m ( a minimum line land of less than 15kN/m) provided the water is kept away from the foundation.
A grade on beam supported by the soil below can also be use while the most expensive and structurally sound option is to use grade beam supported on pier or pilling

tossen:
That would b nice if the building is in a dense area where it isnt the tallest and is not susceptible to strong winds.

I still disagree with your assertion. Wind load will only have effect on the building if it it produce lateral restrain to your build. When the floor is not designed to serve as a diaphragm ( a structural member that transfer lateral load to vertical resisting members)

Miscellaneous:
please, do u mean there will be no beams under the slab? For a framed structure? pls I would appreciate some explanations

There are beams but these beams are of the same depth as the rib ( the small beam of the waffle). These beams are wider than normal beams in solid slab construction ( width greater than 225mm in most cases).

Miscellaneous:
oga abdul.... I'm in deep mess. How do I learn this design of beams, slab, stairs easily... lecturers are not helping because of negligence. You see, I bought oyenuga but that book is clearly not helping.... more like for those who already know the design before hand. Even Bungey is not helping... wat do u think I do? Exam sef dey run come near me like say I carry magnet for body...

Check out the following books
1. Reinforced concrete: design theory and examples ( first and second edition) by T. J. MACGINLEY and B. S. CHOO

2. Reinforced concrete design to BS8110 - simply explained (A H ALEN)

3. Reinforced concrete designer's handbook (C E reynolds and J C Steadman.

4. Reinforced concrete design ( Bill Mosley, John Bungey and Ray Hulse).

These books were very helpful to me during my undergraduate years on reinforced concrete design.

I will also advice you to get all the BS 8110 for reinforced concrete design, steel table and structural detailing to Bs 8110. You need to also get BS 6399 loadings for building. These codes will make it easy for you to do your design.

Structural design requires lit of simple mathematics unlike structural analysis that requires advanced and vigorous maths. What you need to do is devote more time to it, understand all the steps involved and prepare your mind towards it.

During my undergraduate years, grade (gp) was secondary to me, understanding the design was more important to me. I study these things to be able to do the design, so I use lit of practical examples like working real architectural drawings instead of those simple panels giving in the classrooms.

BITSWORKS:
Hello, the information you provided for the foundation is a bit bare but I guess you are more concerned about the labour/supervision cost.

The type of foundation will determine the labour cost as a strip foundation will be cheaper than a raft in terms of labour cost and work to be done. Kindly clarify this and I might be able to make a judgement call because I do not disparage other colleagues cost based on incomplete information.

Kindly note you can always negotiate whatever cost is thrown at you as long as its fair to you and its fair to the engineer building. Cheers.

As you can see from the drawing he uploaded, the foundation type is pad footings and strip footing.

tossen:
The only disadvantage is that you incur a lot more cost in painting and rendering. Also, you need a high skilled artesan to carry out the finishing works in order to produce a perfect final finish. Also, it is not advisable in areas where there will be a lot of traffic. As it isnt designed to bear such load but in places like libraries, etc. It also provides great aesthetics.

I don't think you incure more cost from rendering ( under the decking), If any of polystyrene, clay block or concrete block is used. The rendering is plastering of the under decking after the work has been completed, similar operation is carried out on solid slab under decking.

Hall ways in build, school and hotels have life load of 3.0kN/m2, such load is can be carried continently by waffle slab.

Waffle slab without permanent former such as polystyrene or clay block cost more during finishing and requires good artisans

n3xt:
Good one but what are the disadvantages.

It is not suitable for heavily loaded floor like that of garage, store, factory etc.

Horlawoomey:
This is so explanatory, I wish you were my lecturer in school, well the best Engineers do not always end up in the classroom.

To me those flat slabs require more attention during construction because of the punching stress those columns will be exerting on the slab without beams. I read somewhere that if the slab is not having column head, part of the column and the slab should be casted monolithically.

Secondly, I am on a project where they use waffle slab for the decking and from what I observed on the bottom the beam width is not more than 75mm between the sandcrete blocks, what do you see to this ?

Actually it is possible to have a rib beam width of 75mm if they use a single reinforcement like Y16 bottom for the rib beam without links and top reinforcement.

The size of rib beam is govern by fire resistance (cover), bar size, spacing of bar within the section.

Flat slab is the most technical among all slab type to detailed and execute. It contains lot of reinforcement as a result of punching shear along the column areas. flat slab without column head or drop down panel can also be constructed normally provided the punching shear along the critical perimeter are adequately provided for during the design and detailing of slab

DonnyE:
Mathematically speaking,you can still do well and even graduate with a first class,cos your first year is only about 10% of CGPA.However u seriously need to be more focused and dedicated to your education as u have been on NL

Mathematically speaking, I don't think so. Your first year is 2/9 x 100 = 22.2% of your cgpa. I graduated from fut Minna and I know the system work.

true2home:
The above explanations covered the idea for its use. I will not recommend it in Nigeria because the method requires close supervision and clear structural mathematical calculation. Less me just say there is less room for mistake when building such deck. The iron used has to be the right Fy and the concrete right Fc as well. Concrete characteristic is compression strength, while iron's is tension. Tension is experience in the bottom of a slab while compression is exact on the top section of a slab. if the bottom section does not deform excessively, then the concrete at the bottom area of a slab do not serve much engineering purpose other then composition for the iron rod. Anyways, i have to stop here before i loss non-engineering NL

All method of slab construction requires close supervision and clear mathematical calculations.
Waffle slab is as straight forward as one - way solid slab or two - way solid slab, I think flat slab is more technical than even this waffle slab.

For all type of slab you need the right steel strength and concrete strength.
A one way slab behave like a continuous beam where the span is sagging ( bottom Fibre is in tension) while the continuous support is in hogging (top Fibre at the support is tenaion).

A two way slab behavior is dependent on the end conditions and for this type of slab we have about 9 different end Conditions, namely
1. Interior panel
2. All edges discontinuous
3. One short edge discontinuous
4. One long edges discontinuous
5. Two short edges discontinuous
6. Two long edges discontinuous
7. Adjacent edges discontinuous
8. One short edge continuous
9. One long edge continuous.

For these two way slab design code is use to determine both the positive and negative moment for design purpose.

For ribbed and waffle slab.
Ribbed slab is like a one way slab where the solid concrete section is replaced with series of ribbed parallel to one another at a reasonable space based on the life load, span of slab and the type or former to be use. It is made up of topping, rib beam and former which can either be temporary or permanent. The analysis of the rib is carried out like that of one way slab where the span and support moment and shear is gotten through beam analysis or using appropriate formulas from bs codes.

Waffle slab is like two way slab where the rib beam is in both directions. The ribbed intersect each other to form a box that is either filled using polystyrene, clay block or sancrete block.

SilvanusII:
NOTE: I am an agriculturist not an engineer but I am asking my question on basic physics knowledge.
You have listed advantages. Good. But what exactly are the waffle balls made of? If they do not allow sound thru and are good in places with high temparatures, I figure that the balls are hollowed out with air spaces inside to trap sound and heat. IF they are thus hollow, how can they support decking? They'd be too light na. How durable are they sef?
At least the waffle slabs look dense enough to me. The material is packed tight and should be strong.

Question like '' how can they support decking '' is the misconception people havd with these materials. They are not designed to support decking, they are designed to replace some concrete section that are useless in the slab section in the first place.
The ribbed beam with reinforcement support the slab or decking load. The slab is designed with these grid beam spaced at mostly 600 center to center in the case of polystyrene slab, the beam carries the floor load while the 600mm square spaced between these beam is occupied by poly slab.

ewizard1:
IMO

Sound Proof - Agree
Heat Insulant - Agree
Ligth Weight - Agree

Cost Less - err... errrrr... Agr... mbanu! DISAGREE!

Yes, less concrete volume but the reinforcement is doubled if not quadrupled. The (Waffles, Foams, etc) fillings would not cost so cheap either!

***NOTE : Not a Civil Eng/Construction Personnel, just using my common sense!

It cost less.
The reinforcement is much less because you only reinforced the rib beam with 2y 12 down and nominal top reinforcement and use y8 spaced @ 300mm center to center in most cases ( though reinforcement details depend on your structural designs) . The topping is provided with Iron mesh or light mat reinforcement preferably y8 spaced at 300mm center at the middle of the topping to control temperature shrinkage and cracking.

The concrete section of the beam is smaller (150mm x 250mm for a simple residential building) with a topping around 50-75mm the remaining section of the slab is replaced with polystyrene pod which is cheaper

EgunMogaji:
@AbdulWastecx, weren't you proposing something similar?

Yes sir, I have designed a couple before. The one I was proposing is using polystyrene as the former instead of this bubble they have here.

Most Nigeria home owner are not too comfortable with it because they perceived the material to be too light weight.

Our conservative mentality about what can work and what cannot. People don't know that the polystyrene is just occupying concrete space below neutral axis at places where they are not useful. The major structural component is the ribbed beam which is closely spaced. The ribbed beam in waffle slab do all the structural work while the polystyrene pod help to reduce unwanted concrete section thereby reducing weight and cost of not only the slab but also other dependent structural members like beams, columns and foundation footings since the load transfered to these members will be significantly lower than that from an equivalent solid slab

HOLAROCKDAY:
To the civil Engineers, Builders in the forum.
Base on my pictures below, A friend of mine sent me this pic asking me what type of slab it is. And where can it be use, the reason of putting the waffles ball in between the reinforcement. To cut the story short, an explanation on the slab. I believe you will help me out with these.

This is a waffle slab with permanent shuttering (former). Waffle slab is a slab with rib beam in two direction (different from ribbed slab with rib only in one direction.
The ribbed are space at a regular distance between each other based on formers, life load and code specifications.

Waffles slab is made up of
1. Topping
2. Series of rib beam accros both the short and long span of the slab.
3. Former ( the bubble above, hollow block, clay block, plastic pod, polystyrene pod etc) which remain part of the construction after the Formwork is removed.

In most cases the waffle slab is designed in such a way that the topping is not consider to contribute to structural strength but only to linked the rib beams together. The topping can also be made of concrete of not necessarily of the same strength as that used in ribs.

The former (polystyrene pod, bubble or clay block) are not consider to contribute to the slab strength in the design calculation most time.

The major advantage of these floor is the reduction in weight achieved by removing part of the concrete section below the neutral axis and replacing that with lighter weight materials. These types of construction are economical for building where there are long spans, over between 5m to 6m with light to moderate life load (1.5 - 3kN/m2), such as residential houses, schools, hospital, hotels etc. They would not be suitable for floors having heavy load like warehouse, production facilities, garage etc

twinskenny:
Well done Engr

Thanks sir

n3xt:
Foundation Problems | Why you should keep water away

Within 3 months, we raised a new structure for the client and broke the compound floor, took off excess sand and introduced perimeter drain at 1.2m depth below the assumed natural ground level, introduced inverted T beam for the 600mm high fence ground beam.

It's almost 5 years now that we implemented this fix, the fence hasn't fallen down and we haven't been called back for any maintenance job bigger than what the clients wife and kids living in the house can manage.

Pic 1: The problems created when too much soil is used to backfill a foundation. Especially laterite fillings.

Pic 2 & 3: The reconstructed fence wall been raised.

Pic 4: The new construction

Very good pictures and explanation Mr n3xt.. Back filling sloping terrain with very deep foundation depth create lot of problem to the sancrete block used since this blocks will be retaining these earth.

There was this new store constructed close to one of our site in katampe ( abuja). The depth of the ground floor was around 600mm plus whatever height to the foundation level. The problem started when the store was put into use to store about 800bags of cement. The load of cement couses serious Crack below the dpc level. These failure was due to so active pressure on theses walls

AZUH:
I m only asking for solutions . I cAn do it if I know to work on . That is why I uploaded the picture @ fastshipping . Thanks anyway

You have to upload more pictures and state the problem you encountered before we can provide you with solutions

AZUH:
Please this house has one block up and one block dawn . We where planning going on landscaping but when we find out . One block was used . We got confused. If you are the contractor to this building what will you do ? Thanks

What is the major problem bros?
Do you mean the dpc level is too low from the natural ground level because the height is 225mm?


You have to provide more information about what you want to correct before you can get a good solution

africanpea:
Hmmmm... I'm interested too. What would it cost to build a four bedroom bungalow to plastering level with toilet and bath ensuite, a sitting room, dinning section, kitchen, store and a small laundry room? No pool, gym and other luxuries.

I think it will be cost effective to build a Bungalow like that.
You will need a design first and then a good bill of quantities detailing all the materials and workmanship needed including the job duration.
Check out these designs and ongoing bungalow construction

anthoniosp:
Pls..I would like to inquire for a place like nassarawa ..I and my family want to move there..I want a place with

Luxury finishing
Large master bedroom
Large dining room
One large kitchen
And a small swimming pool
With outside gym

Nassarawa Is a cool place to live and cost of living is relatively small.
You can contact us for any professional help sir... we are familiar with that axis.

For this can of development, you will need a minimum of 100ft x 100ft plot of land

More updates of the reinforcement work

More updates

Saintee2009:
Sorry sir, i "think" there was a minor mistake in the calculation. (1050 + 300 = 1350) thereby making it 12m(length of reinforcement in m) divided by 1350mm(1.35m) = 8.888nos.
On other hand, i guess you used 1.5m so as to get accurate figure ( right? Just a little clarification needed. Thank you sir.

The reason I use 1.5m instead of 1.35m is personal. I always like to use want to get some whole number answer

Saintee2009:
I noticed the hollow blocks were not filled with concrete prior to casting of the dpc. A little insight sir. Thanks sir.
Sorry for my numerous questions sir.

They were filled with broken blocks

Saintee2009:
Good day sir, sorry for dragging you bk a bit. Does that mean we'll have to dig down an additional 250mm for the isolated footing? Making the total (900 + 250) Moreso, why 250mm when the depth of the isolated footing is 450mm? Thanks for your usual clarification. Huge fan. Graduate civil engineer

You have to dig 300mm, where we have 50mm as the blinding while 225mm is the Isolated pad footings.

The reason why I have 225mm inside after 900mm is that the foundation is a combination of isolated pad footings and strip footing, so the other strip of 225mm plus the initial 225m will equal to 450mm. Note: since the pad and strip are monolithically cast together.

More updates

Reinforcement detailing work

Stair case formwork

dudubody:
what is the reasonable amount to pay pls

If each of the four bedroom flat are detached, N400,000 each per flat is reasonable

n3xt:
Rough is never good, Bro.

Yea oga n3xt