₦airaland Forum

saydfact:
@EgunMogaji and Calculation

Thanks for the note....

Please, I need to ask question concerning pad foundation. In pad foundation how do we determine the depth of excavation from natural ground level?
Is it when the excavation get to hard soil level or there is factor that determine it. Thanks for your write up as it really help me to understand some stuff on building and design.

calculation:
Please, I need to ask question concerning pad foundation. In pad foundation how do we determine the depth of excavation from natural ground level?
Is it when the excavation get to hard soil level or there is factor that determine it. Thanks for your write up as it really help me to understand some stuff on building and design.

Pad foundations are used on hard soil... (remember I said stabilization is needed if the soil is soft, at the end of stabilization, the soil becomes hard)

Depth of pad foundation is usually between 900mm - 1500mm

What matters most is the size of the pad I.e. Length and Breath and the reinforcement in it.

Thanks

calculation:
Please, I need to ask question concerning pad foundation. In pad foundation how do we determine the depth of excavation from natural ground level?
Is it when the excavation get to hard soil level or there is factor that determine it. Thanks for your write up as it really help me to understand some stuff on building and design.

The depth of the excavation for pad foundation will be determined by the structural engineer designing the foundation. The depth depends on so many factors such as the bearing capacity of the soil, size of the column, load the column is carrying etc.

4gunners:
The depth of the excavation for pad foundation will be determined by the structural engineer designing the foundation. The depth depends on so many factors such as the bearing capacity of the soil, size of the column, load the column is carrying etc.

I guess this is a more technical answer... Thanks

saydfact:
Wikipedia defines foundation as: A foundation (or, more commonly, base) is the element of an architectural structure which connects it to the ground, and transfers loads from the structure to the ground. Foundations are generally considered either shallow or deep.

It is advisable to know suitability of each types of foundation before deciding which best suit your design type and soil. We would discuss them briefly below:

Types of Foundation and their Uses

The following are different types of foundations used in construction:

1. Shallow foundation
* Strip foundation
* Pad or Individual footing foundation
* Raft or Mat foundation

2. Deep Foundation
* Pile foundation

We would only focus on the shallow foundation in our discussion here;

1a. Strip foundation

Strip footings are commonly found in load-bearing masonry construction, and act as a long strip that supports the weight of an entire wall. These are used where the building loads are carried by entire walls rather than isolated columns.

This type of foundations are used on good firm soils - and majorly for bungalows because the walls of this type of building are all load bearing walls (i.e transmitting load from the roof, down to the foundation).

[img]https://2.bp..com/-5ZMZ_cVthX8/WobIAiulryI/AAAAAAAADbQ/D4R5U17krIAPSyt6XVCUS0bNsD7otWfbwCLcBGAs/s320/strip_rein.gif[/img]

Looking at the pictures above, you would notice the ground in question is a either rocky or clayey, coupled with the fact we're building a bungalow.

Recommendation: If you have a strong, clay or rocky soil and you're building a residential bungalow on it - then the best foundation to use is a Strip Foundation, the rule however changes if you're building a warehouse (double volume) because there are less load bearing walls to support the roof above - this this case, the pad foundation (discussed below is the right foundation to use)

[img]https://4.bp..com/-7mep1G1ck9Q/WobINAqAYFI/AAAAAAAADbU/fz2q7uQ7bnE-lhFTIicAOao044nzkyI-wCLcBGAs/s320/strip2.jpg[/img]

Note: Strip foundation could be reinforced or plain (without reinforcement)

1b. Pad foundation

Pad foundations are used to support an individual point load such as that due to a structural column. This type of foundation has more to do with the type of structure rather than the type of soil. It could be used on both strong and weak soil, however unlike on strong soil, its use on weak soil requires stabilizing the soil before considering pad foundation.

Pad foundations are used for structures that transmit load to the foundation via columns - and are used for warehouses, workshops, and framed structures (in this cases, the block-walls are NOT load bearing) all load are transmitted through columns or a combination of columns and beams.

[img]https://4.bp..com/-qiRqyD0SJbo/WobIdWeQlwI/AAAAAAAADbY/a8QzxbcuYJ8L1jPBQhwAMZ_LGaP7cS1ZwCLcBGAs/s320/pad.jpg[/img]

Recommendation: If you're building a warehouse, workshop or structures that have limited of no wall partition, then this is the foundation to use - It can be used on strong and weak soil. One weak soil, the soil has to be stabilized and left to settle / rammed mechanically before the pad can be used. The size of the pad foundation and columns are determined by

In good soil areas and for storey buildings, a combination of strip and pad foundation can be used to reduce cost, or pad foundation could be used (solely) where the storey building is a frame structure.

The columns on pad foundation could be made of concrete or structural steel (below pics shows a structural steel on pad foundation)

[img]https://1.bp..com/-pKbm1pN3_g0/WobInRoxnNI/AAAAAAAADbg/w6SRl8t97ZI3sB9L-an2Qqzc5EBBnMBAgCLcBGAs/s320/pad2.png[/img]

[img]https://4.bp..com/-D9gxbI1ktFU/WobLq2A-gOI/AAAAAAAADcA/7wTdm3Mo3A43YUlwekpVVvJkV0fZDoW4gCLcBGAs/s320/pad3.jpg[/img]

1c. Raft foundation

A raft foundation is a reinforced concrete slab under the whole of a building. i.e 'floating' on the ground as a raft floats on water. Raft foundation are used on swampy, waterlogged or sandy (collapsible) soil. This type of foundation spreads the load from a structure over a large area.

[img]https://3.bp..com/-iFVvnmXt5yE/WobJA9Q5NqI/AAAAAAAADbk/CiQm4Fw6M8c2TQe5IrrWUNDgwaCtEXpEQCLcBGAs/s320/raft%2B1.jpg[/img]

It is also used for basement floors even in strong soil with a retaining (concrete) wall around it.

Recommendation: If you're building a bungalow, 1 storey or 2 storey structure on a weak soil, then raft foundation is the foundation to use. They are generally constructed on a compacted (hardcore) base for best results and a layer of 50mm weak concrete (blinding) laid to allow a level surface for forming of the raft.

[img]https://2.bp..com/-BG3AfNc1mEU/WobJHyv3trI/AAAAAAAADbw/Y71jdYza--8WI6VyUuGWk6Qr6wRhQh0HQCLcBGAs/s320/raft2.jpg[/img]

[img]https://1.bp..com/-n3OhZok44JA/WobJHtp7MoI/AAAAAAAADbs/MzAGu7giRWkTo4EEfpoZPy40weP1Nd4cACLcBGAs/s320/raft3.jpg[/img]

2. Pile foundation

Pile foundations are principally used to transfer the loads from superstructures, through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth.

[img]https://4.bp..com/-FUl04G9BodY/WobMfqW5TBI/AAAAAAAADcM/wBTcU9W5ussNiAle4hvl_pOEH3ZpH5naACLcBGAs/s320/pile1.jpg[/img]

[img]https://2.bp..com/-9tfM3q7ybjw/WobMfkIG9RI/AAAAAAAADcI/ZE8gVWALcMUKLqj6cm-x7BO96Gcqgk5aQCLcBGAs/s320/pile2.jpg[/img]

In whatever type of foundation used, waterproofing membrane should be considered.

Disclaimer: Pictures used for this reports are random pictures gotten from the internet, we do not claim ownership.

Thanks....

source: https://constructionfactz..com.ng/2018/02/choosing-right-foundation-for-that.html

the model of the raft you showed and the raft you posted in practice are they the same?

bomsilaga:
the model of the raft you showed and the raft you posted in practice are they the same?

YES

4gunners:
The depth of the excavation for pad foundation will be determined by the structural engineer designing the foundation. The depth depends on so many factors such as the bearing capacity of the soil, size of the column, load the column is carrying etc.

Thanks sir for your technical input. I now understand more better.

4gunners:
The depth of the excavation for pad foundation will be determined by the structural engineer designing the foundation. The depth depends on so many factors such as the bearing capacity of the soil, size of the column, load the column is carrying etc.

Thanks i can relate better now. More Grace to your elbow.

Hello man, i want to start sand filling a land in preparation for building soon and will like to ask;
1. how much of the top soil (depth) has to be excavated before sand filling to avoid soil movements in future
2. how long should the sand fill be left before the foundation commences
3. any other tips to achieve solid foundation

recommended foundation type - raft
location - swampy/waterlogged
planned build - duplex (ground & first floors)

thanks

HI, (My reply in bold)

megacontrol:
Hello man, i want to start sand filling a land in preparation for building soon and will like to ask;
1. how much of the top soil (depth) has to be excavated before sand filling to avoid soil movements in future
Not much, just ensure you remove all the bad soil i.e soil that has green growing on it, debris and rubbish dumped on the site, wood and all material that can decay, plastic etc - if you're not sure just remove about 100cm of top.

2. how long should the sand fill be left before the foundation commences
About a year is perfect but if you don't have that much time, fill about 450mm high and compact mechanically (rammer) until you reach the required height ie (wet and rammer in layers)

3. any other tips to achieve solid foundation
Get qualified men on the job, ensure adequate rebar spacing, use appropriate rebar (iron) and seek professional advice etc

recommended foundation type - raft
location - swampy/waterlogged
planned build - duplex (ground & first floors)

thanks

GoodLuck

very interesting topic! and I love the simplicity I n your explanation.
I want to ask: if you're using a pad foundation, what happens to the rest o the wall foundation? do you just lay blocks from the floor or do you use a sort of strip foundation for the rest of the wall?

dubuntu:
very interesting topic! and I love the simplicity I n your explanation.
I want to ask: if you're using a pad foundation, what happens to the rest o the wall foundation? do you just lay blocks from the floor or do you use a sort of strip foundation for the rest of the wall?

Any of the two methods you mentioned above could be used, depending on what you're building and the structural design type also depends on the material to be used in construction...

thanks for the positive comments.

Evening Followers.

Kindly check out my latest post here >> https://www.nairaland.com/5002180/what-did-he-wrong-why#75413259

Thanks

Contact us today for your soil test and Piling works,we will give you a well detailed soil test report of your land and recommend the type of foundation that can retain your structure.
Our soil test comprises the Dutch cone Penetrometer test and the percussion borehole in order to achieve the greatest knowledge of what is beneath the soil on which your structure is to be constructed.
soil test helps to know whether there will be need for piling or not.
The report will also be used for your building approval
Dont consider the money, please it is advisable to do soil test before erecting your building. Thanks for your patronage.
You can call or WhatsApp us on 07033221554