Pile screw foundation with own hands – possible problems | With Your Hands – How To Make Yourself
All important nuances of screw pile foundations
Screw piles are steel pipes with steel blades, providing bearing soil capacity with intact structure, installed by manual or mechanical ways.
Screw pile foundations – a modern technology of quickly installation of reliable basement on screw pipes. These details have blades that are tightly screwing into the ground, creating a secure base for a future building.
The main advantage of such a basis type is the possibility not to use complex special equipment. However, you need to know rules of its pouring!
The foundation choice
How to start any building, home, cottage? Well, of course you need to start with a foundation! Reliable and sustainable basements give more durable service life. For normal conditions and soils the perfect choice in this situation is quite wide: strip foundation, columnar, block. For house construction on weak, unstable or peat soils the better option will be a screw pile basis.
This type of foundation technology is not new; it has been developed and patented for about two hundred years ago by the Irish engineer Alexander Mitchell.
He invented and suggested the use of screw piles and anchors for installing beacons in estuaries and sandy shallows.Today, this technology is widely used in the field of low-rise housing and serves as a basis for all kinds of wooden frame houses. In some cases, it is also used while building block houses.
Before to start building, you should consider and decide what will be the type of your basement, in order to avoid rapid deterioration, cracks, drawdowns, or premature destruction of every house.
For soft ground a screw pile basis is just the perfect choice.
It is quickly and easily installed, regardless of terrain irregularities and serves for a long time – at least 100-150 years, and with special processing – even 200.
Advantages and disadvantages
Several great benefits:
- Quick installation process.
- When mounting it is not necessary to carry out excavation work and leveling your plot.
- Relatively low cost.
- High margin of details strength. They are immediately prepared to accept the load, provided by a project. You do not need to wait until a basement is settled.
- Since this technology is used in construction of buildings in water, so in case of area flooding your building will not suffer.
- The possibility of expanding since you can attach a new foundation to the existing one.
- The ability to carry out works at any time of the year and during all weather conditions.
- The ability to simultaneously run utilities.
- Quick and easy repair.
- Details are not afraid of cold, they are resistant to seismic events, do not require special waterproofing or violate the integrity of surrounding ground, which is particularly relevant in the context of weak soils.
- Each pile can withstand a load weighing several tons.
However, this foundation type has its drawbacks: while installing you need to contact professionals, because the stony terrain can damage main details and as a result they may get corrosion. With unscrupulous mounting you can accidentally deviate from the building design increasing or decreasing the basement size.
The mounting procedure
The installation process is simple and clear, in most cases you can cope with it alone:
- Determine the house location on a plot;
- Mount a corner (base) screw pile;
- According to your layout, set the rest of details;
- Perform the pile trimming by level;
- Mount a headroom on details top;
- Make the foundation tying with channel bar or beam.
When installing your basement necessarily ensure that piles are occupied strictly vertical position, checking it with a building level.
When constructing a screw pile basis in the city you need to request communications card, which may take place under your plot, or check the estimated area with the help of a cable detection instrument.
Outside the city, such precautions are generally unnecessary.
Screw pile foundations are great, because they might be used in almost any conditions without destroying the natural terrain.
You can build very carefully a house on the forest glade without damaging trees, or, for example, a cottage on a hillside.
As well as a pier for boat or fishing at your favorite backwater will not affect the natural landscape or harm the natural environment. And if you are not lucky with marshy areas, and then there are simply no other options!
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What type of pile Foundation is suitable for your home?
Pile-foundation foundation for a wooden house with your own hands: reviews
If you decide to build a pile-grillthe foundation for a wooden house, it is first necessary to get acquainted with reviews that are left by home masters and professionals involved in carrying out such work.
Such a construction is a support on which the load from the entire structure is assigned. In this case, piles or screw products are used as piles. Grillage, in turn, performs the function of dislocation load from the building.
Formation grillage is carried out with the help of beams or slabs, which are formed in a single system.
The pile-foundation foundation under the wooden housecan be built on the territory, the soil of which is problematic. This mainly applies to clay soils. The base, formed using piles, allows you to transfer a significant load to hard rocks that are located deeper than the top layer. It should be noted that this type of foundation can also be built on favorable, conventional soils.
Modern masters resort to constructionpile-grill foundation for the reason that such a system has a high load-bearing capacity.
Among other things, private developers say that they are attracted by the economy, which can be achieved due to a small amount of excavation.
Reading reviews, it is worth highlighting that the masters use this basis when it is necessary to build wooden structures, as well as structures of frame and shield type.
Reviews about materials piles
The pile-foundation foundation under the wooden housecan be built using different materials. Each of them is distinguished by its quality characteristics and duration of operation.
Some consumers choose wooden supports, while other buyers most often prefer metal or reinforced concrete products. It is worth noting that the wooden piles of the master are chosen in the event that they will be rendered an insignificant load.
Preference for this is coniferous wood, the most suitable pine.
The pile-foundation foundation under the wooden housecan be erected with the help of reinforced concrete pylons. They are most in demand today and represent hollow pillars, which can have a square or circular cross-section.Metal supports, as practice shows, need additional processing with special compounds that can prevent corrosion processes. Wooden supports, according to consumers, are the most short-lived.
After a while they start to smolder in the ground.
Reviews of the pros of the pile foundation
If you decide to use for constructionpile-foundation foundation under a wooden house, it is initially recommended to get acquainted with the positive and negative sides of this type of foundation.
Most often, the owners of houses that were built using this technology note that the uniqueness of the design is that it can be formed on different soils. However, it is worth to refuse to carry out works, if magmatic soil or sedimentary soil is found on the territory.
Many residents are attracted by the fact that construction takes very little time. Then you can start work even in the cold season. Future owners note that their choice was influenced by the excellent bearing capacity of the base.
If you compare with the ribbon foundation, then the described type of construction is much cheaper.
Tips for the home master
Pile-foundation foundation, reviews about whichyou have the opportunity to read in the article, can be easily erected independently. To do this, it will only be necessary to screw the supports into the soil for a certain distance. After using the Bulgarian, you should cut the piles in such a way that they are at the same level.
Reviews of the minuses
Before the start of construction, you mustto familiarize with the disadvantages of the foundation.
Among them, modern consumers note the impossibility of carrying out manipulations without using special equipment and tools. This increases the cost of work.
If there is a rocky ground in the development area and there is a layer of limestone and stones that is hard, it will be impossible to form a pile foundation with a grillage.A number of professional builders give upThis type of foundation for the reason that under it is impossible to lay a warmed basement room.
At the first stage it is rather difficult to make calculations, that's why you will have to entrust conducting these works to professionals.
The pile-foundation foundation, the shortcomings of which are described in the article, can not be analyzed after the supports are pinned to the ground. This excludes the possibility of detecting damage.
Technology of erection
Pile-foundation foundation by own hands canbe erected according to a certain scheme. To begin with, it is necessary to form the wells using a manual drill. At the next stage, a formwork is installed, the upper edge of which must be slightly above the ground surface. The material should be raised by 300 millimeters.
Further, pipes are formed of roofing material, the diameter of which should be equal to the dimensions of the well. Then how to damp these elements is necessary for 300 millimeters lower in comparison with the pits themselves. After the resulting formwork is reinforced, for which it is possible to use metal rods.
The next step will be pouring the concrete mixture.
You can perform grillage using an iron orconcrete beam. To do this, between the pillars should dig a trench, the depth of which should be equal to 30 cm. After the sand is poured, covers the roofing material, and also the formwork is installed. In the formed space is poured concrete.
What is Pile Foundation? Types of Pile Foundation – Civil Engineering
Foundations provide support to the structure, transfers the loads from the structure to the soil. But the layer at which the foundation transfers the load shall have an adequate bearing capacity and suitable settlement characteristics. There are several types of foundation depending on various considerations such as-
- Total load from the superstructure.
- Soil conditions.
- Water level.
- Noise and vibrations sensitivity.
- Available resources.
- Time-frame of the project.
Broadly speaking, foundations can be classified as shallow foundations and deep foundations. Shallow footings are usually used when the bearing capacity of the surface soil is adequate to carry the loads imposed by a structure.
On the other hand, deep foundations are usually used when the bearing capacity of the surface soil is not sufficient to carry the loads imposed by a structure.
So, the loads have to be transferred to a deeper level where the soil layer has a higher bearing capacity.
What is Pile Foundation?
Pile foundation, a kind of deep foundation, is actually a slender column or long cylinder made of materials such as concrete or steel which are used to support the structure and transfer the load at desired depth either by end bearing or skin friction.
Pile foundations are deep foundations. They are formed by long, slender, columnar elements typically made from steel or reinforced concrete, or sometimes timber. A foundation is described as 'piled' when its depth is more than three times its breadth.
Pile foundations are usually used for large structures and in situations where the soil at shallow depth is not suitable to resist excessive settlement, resist uplift, etc.
When to Use Pile Foundation
Following are the situations when using a pile foundation system can be
- When the groundwater table is high.
- Heavy and un-uniform loads from superstructure are imposed.
- Other types of foundations are costlier or not feasible.
- When the soil at shallow depth is compressible.
- When there is the possibility of scouring, due to its location near the river bed or seashore, etc.
- When there is a canal or deep drainage systems near the structure.
- When soil excavation is not possible up to the desired depth due to poor soil condition.
- When it becomes impossible to keep the foundation trenches dry by pumping or by any other measure due to heavy inflow of seepage.
Types of Pile Foundation
Pile foundations can be classified function, materials and installation process, etc. Followings are the types of pile foundation used in construction:
The following diagram is representing pile foundation types discussed above.
These piles are briefly discussed below.
This type of pile is mostly used to provide lateral support. Usually, they resist lateral pressure from loose soil, the flow of water, etc. They are usually used for cofferdams, trench sheeting, shore protection, etc. They are not used for providing vertical support to the structure. They are usually used to serve the following purpose-
- Construction of retaining walls.
- Protection from river bank erosion.
- Retain the loose soil around foundation trenches.
- For isolation of foundation from adjacent soils.
- For confinement of soil and thus increase the bearing capacity of the soil.
Load Bearing Piles
This type of pile foundation is mainly used to transfer the vertical loads from the structure to the soil. These foundations transmit loads through the soil with poor supporting property onto a layer which is capable of bearing the load. Depending on the mechanism of load transfer from pile to the soil, load-bearing piles can be further classified as flowed.
End Bearing Piles
In this type of pile, the loads pass through the lower tip of the pile. The bottom end of the pile rests on a strong layer of soil or rock. Usually, the pile rests at a transition layer of a weak and strong slayer. As a result, the pile acts as a column and safely transfers the load to the strong layer.
The total capacity of end bearing pile can be calculated by multiplying the area of the tip of the pile and the bearing capacity of at that particular depth of soil at which the pile rests. Considering a reasonable factor of safety, the diameter of the pile is calculated.
Friction pile transfers the load from the structure to the soil by the frictional force between the surface of the pile and the soil surrounding the pile such as stiff clay, sandy soil, etc.
Friction can be developed for the entire length of the pile or a definite length of the pile, depending on the strata of the soil.
In friction pile, generally, the entire surface of the pile works to transfer the loads from the structure to the soil.
The surface area of the pile multiplied by the safe friction force developed per unit area determines the capacity of the pile.
While designing skin friction pile, the skin friction to be developed at a pile surface should be sincerely evaluated and a reasonable factor of safety should be considered. Besides this one can increase the pile diameter, depth, number of piles and make pile surface rough to increase the capacity of friction pile.
Soil Compactor Piles
Sometimes piles are driven at placed closed intervals to increase the bearing capacity of soil by compacting.
Classification of Piles Materials and Construction Method
Primarily piles can be classified into two parts. Displacement piles and Non-displacement or Replacement piles. Piles which causes the soil to be displaced vertically and radially as they are driven to the ground is known as Displacement piles.
In case of Replacement piles, the ground is bored and the soil is removed and then the resulting hole is either filled with concrete or a pre-cast concrete pile is inserted.
On the basis of materials of pile construction and their installation process load-bearing piles can be classified as follows:
Timber piles are placed under the water level. They last for approximately about 30 years. They can be rectangular or circular in shape. Their diameter or size can vary from 12 to 16 inches. The length of the pile is usually 20 times of the top width.
They are usually designed for 15 to 20 tons. Additional strength can be obtained by bolting fish plates to the side of the piles.
Advantages of Timber Piles-
- Timber piles of regular size are available.
- Easy to install.
- Low possibility of damage.
- Timber piles can be cut off at any desired length after they are installed.
- If necessary, timber piles can be easily pulled out.
Disadvantages of Timber Piles-
- Piles of longer lengths are not always available.
- It is difficult to obtain straight piles if the length is short.
- It is difficult to drive the pile if the soil strata are very hard.
- Spicing of timber pile is difficult.
- Timber or wooden piles are not suitable to be used as end-bearing piles.
- For durability of timber piles, special measures have to be taken. For example- wooden piles are often treated with preservative.
The precast concrete pile is cast in pile bed in the horizontal form if they are rectangular in shape. Usually, circular piles are cast in vertical forms.
Precast piles are usually reinforced with steel to prevent breakage during its mobilization from casting bed to the location of the foundation. After the piles are cast, curing has to be performed as per specification.
Generally curing period for pre-cast piles is 21 to 28 days.
Advantages of Pre-cast Piles
- Provides high resistance to chemical and biological cracks.
- They are usually of high strength.
- To facilitate driving, a pipe may be installed along the center of the pile.
- If the piles are cast and ready to be driven before the installation phase is due, it can increase the pace of work.
- The confinement of the reinforcement can be ensured.
- Quality of the pile can be controlled.
- f any fault is identified, it can be replaced before driving.
- Pre-cast piles can be driven under the water.
- The piles can be loaded immediately after it is driven up to the required length.
Disadvantages of Pre-cast Piles
- Once the length of the pile is decided, it is difficult to increase or decrease the length of the pile afterward.
- They are difficult to mobilize.
- Needs heavy and expensive equipment to drive.
- As they are not available for readymade purchase, it can cause a delay in the project.
- There is a possibility of breakage or damage during handling and driving od piles.
Cast-in-Palace Concrete Piles
This type of pile is constructed by boring of soil up to the desired depth and then, depositing freshly mixed concrete in that place and letting it cure there. This type of pile is constructed either by driving a metallic shell to the ground and filling it with concrete and leave the shell with the concrete or the shell is pulled out while concrete is poured.
Advantages of Cast-in-Place Concrete Piles
- The shells are light weighted, so they are easy to handle.
- Length of piles can be varied easily.
- The shells may be assembled at sight.
- No excess enforcement is required only to prevent damage from handling.
- No possibility of breaking during installation.
- Additional piles can be provided easily if required.
Disadvantages of Cast-in-Place Concrete Piles
- Installation requires careful supervision and quality control.
- Needs sufficient place on site for storage of the materials used for construction.
- It is difficult to construct cast in situ piles where the underground water flow is heavy.
- Bottom of the pile may not be symmetrical.
- If the pile is un-reinforced and uncased, the pile can fail in tension if there acts and uplifting force.
Steel piles may be of I-section or hollow pipe. They are filled with concrete. The size may vary from 10 inches to 24 inches in diameter and thickness is usually ¾ inches. Because of the small sectional area, the piles are easy to drive. They are mostly used as end-bearing piles.
Advantages of Steel Piles
- They are easy to install.
- They can reach a greater depth comparing to any other type of pile.
- Can penetrate through the hard layer of soil due to the less cross-sectional area.
- It is easy to splice steel piles
- Can carry heavy loads.
Disadvantage of Steel Piles
- Prone to corrosion.
- Has a possibility of deviating while driving.
- Comparatively expensive.
Pile Foundation: the essence, types, advantage, disadvantages and build with their hands
Before we consider the application conditions, the advantage and disadvantages of raft Foundation, I would to talk about, what is this type of Foundation and what it consists of.
Pile Foundation with his own hands
Pile Foundation is mostly concrete structure, employee in order to withstand the weight of the building, which is built on it, and in order, that would give you create soil load.
Installation of pile Foundation
Pile Foundation consists of piles and caps.
Piles elements of design of pile Foundation, which are long columns, penetrating the soil up to a certain point and transmitting all loads on the soil. Piles can be wood, metal, concrete and reinforced concrete.
The cross-sectional shape of round, square, pyramid. There are hollow and solid piles. According to the method of occurrence in the earth piles are divided into supporting and hanging. Now consider each kind and type of piles.
The wood pile are the most cheap and short-lived option. Manufactured mainly from larch, ate, fir and pine. Used very rarely and then for lightweight structures. That would extend the life of wood piles using various antiseptic, protects against damage of the wood with fungus and other diseases.
The wood pile
The pile of metal often used in the creation of pile Foundation with his own hands. The advantage of the metal piles is speed of installation of the Foundation, independence from the time of year of construction and average durability. Drawback – the high price of material and the need for treatment anti-corrosion agents.
Concrete and reinforced concrete piles are also a popular option. They have the advantage of a good ratio price-quality. Can be manufactured in the factory, and on-site construction (pouring manually). The durability of reinforced concrete piles exceeds 1 century. To create this type of piles with their hands, it is recommended to use a cement M400.Hollow piles represent pipe, which are first installed in soil, and then optionally filled with concrete solution. This type of piles is considered very good, because. when you create a light design to save the cost of material, and when building heavy structures to facilitate the installation of piles into the soil, because. the solution will be poured after complete installation.
Solid piles are a standard option, which makes no sense to stay.
Retaining piles different from hanging the, that at the end, which originally goes in the ground, they have “leg” of greater cross-section, transferring all the load to the soil. This device allows you to withstand more weight (to 9 t to the column).
Hanging piles bars represent the constant cross-section. The load transfer from the piles to the soil by means of friction forces between soil and column. Piles as if “crash” in the soil at a certain depth.
The length of the piles may be different and depends on the type of construction (high-rise building, hozblok, residential house, gazebo, summer kitchen). Basically, the minimum length of the piles is 3 meter, and the maximum, according to some sources, can reach up to 20 meters (but I personally have not met so long).
Step of installation of piles also depends on the design and type of soil, distance ranges from 1,5 to 2,5 meters.
The diameter of the piles also depends on the type of construction. Mainly used piles from 20 cm in diameter.
According to the method of installation of piles in the soil secrete:
Driven piles – installation of piles into the soil with special equipment, which puts the bars vibrating forces or impaction.
Printed piles – first well is drilled, it fits rebar and poured concrete.
Drilling reinforced concrete piles – the finished product, cranes installed in a prepared pit.Screw piles – most easy to installation, represent metallic bars with threads ( screws or drill bits), which is screwed into the soil either manually, or using special equipment.
With regard to piles, it seems to be all that can be said. You should also note, what to create with their hands is recommended to use a drilling reinforced concrete piles or helical. Also be sure to make a pile support in the soil, to ensure sufficient stability of the construction.
Now come to the second element of the pile Foundation – the gratings. The gratings are horizontal, a concrete or metal structure, which binds everything into one pile and serve as the receiver of all loads for a uniform distribution on all the piles.
Classification of foundations a more modest. There are monolithic, prefabricated and precast-monolithic grillage.
Monolithic grillage are made immediately on-site construction pile Foundation with formwork, reinforcing dressings and liquid concrete and mortar.
Prefabricated and precast-monolithic grillage represent the factory of concrete blocks, which are installed at the construction site. Their advantage is the reduction in time to create a pile Foundation with his own hands. The disadvantage is the need for special technique (crane), higher material costs and lower strength of the Foundation.
The gratings can be high and low.
High the gratings are located at low altitude from the earth's surface and transmit all the load exclusively on piles.
Low gratings a better option, because. they are created on the basis of. Removed a small layer of soil (to 30 cm), creates a drainage layer, formwork and concrete is poured a solution.Thus, low grillage transmit part of the loads to the ground, reducing the load on the pile and thereby providing a margin of safety of the entire Foundation.
Low grillage represent the pile-strip Foundation, which we'll talk later.
Where to use pile Foundation?
The conditions of application of pile Foundation, the following:
- Water-saturated soils with a high groundwater level
- Pocasie soil
- Loose marsh soil
- “Floating” the soil
- Soil weak sustainability
In other words we can say, that pile Foundation is suitable for soils with difficult mining and geological conditions.
The advantage of pile Foundation is as follows:
- Lower consumption of materials, than other foundations
- The simplicity of construction of the Foundation
- The durability of the Foundation
- Suitable for the most difficult natural conditions
- The possibility of construction in any weather
- Is used for lightweight structures, and for high-rise buildings
The disadvantage of pile Foundation is required the involvement of a crane and calculation of pile Foundation specialists (we also talk).
Calculation of pile Foundation
Calculation of pile Foundation require the work of specialists. It is not recommended to self-assess pile Foundation, the more, if in the future it will be designed to house.
The reason, that allowed calculation of pile Foundation with his own hands, is, what inexperienced people miss many important nuances. These nuances in the future adversely affect the durability of the structure, material costs for the maintenance and repair of the Foundation, and on the exterior of the Foundation.
We know, that “miser pays twice”, therefore, we strongly suggest you to seek the assistance of professionals, which is no other, accurately determine size, material, the method of installation and other elements create a pile Foundation with his own hands. Experienced architects will first examine the properties of the soil, the depth of the aquifer, tectonics and other factors, who will continue to influence the Foundation.
In addition, specialists will be able to draw the exact circuit you need the Foundation, and to knock out the estimates for all building materials for its construction.
It should be noted, the material costs for the creation of the Foundation amount to about 30% all costs for the construction of a building, therefore, the payment of specialists is not much change the overall cost of construction, for that will significantly affect its longevity!
How to create a pile Foundation with his own hands
The most popular pile Foundation to give are screw, pile with raft Foundation and pile-strip Foundation, therefore, further we will provide instruction for their construction with his own hands.
Pile-screw Foundation with his own hands
The creation of pile-screw Foundation with your hands is the fastest and most acceptable to country houses. If you are going to build garage either gazebo, pile-screw Foundation is just perfect, because. will have the following benefits:
- The mounting structure can be realized in one working day
- The minimum number of ground works
- Low material costs
- Suitable for any kind of soil
Video tutorial creating a pile-screw Foundation
To start creating a drawing the scheme of screw pile-Foundation, where we expect the exact number of piles. Then purchased ready-made metal screw piles and if they are short, screw them into the ground with rod and a few assistants.
The recommended size of the buildings to create a pile-screw Foundation make up 4*6 meters.
The factory, mainly produced hollow screw piles, therefore, if the future building will be difficult, fill them with a concrete solution, easy – do nothing.Once all the piles will be screwed into the ground, you need to cut them according to the level (you can use a water level) and connect them with metal channel welded to the.
On the channel it is recommended to install the precast concrete framework and further to proceed to the construction of the walls. This is a brief guide to creating a pile-screw Foundation with your hands is considered complete, as you can see, nothing complicated. Next, move on to more complex Foundation – pile with raft.
Pile-screw Foundation with his own hands
Pile strip Foundation with his own hands
This type of Foundation is more reliable and sustainable. Nothing complicated in its construction no, and now you make sure.
Video example of creating a pile-strip Foundation
To begin calculate the size of the Foundation and prepare the area.
Next, using the drill pulls the required number of holes to a certain depth and make a trench for a strip Foundation, then proceed to the creation of piles.
It is recommended to create a small bed of gravel and sand (drainage layer), which carefully stamped. Next, create the waterproofing of the pile, using sheets of roofing material.
Of them make molds, which will be filled piles, linking these molds fishing line and installed in the pit. In molds it is necessary to install the reinforcement of ligation of several rods, diameter 12 mm.
Rebar tied with wire and make that long, whatever she spoke from the pit to 15-20 cm (for further ligation with the grillage).
The mold of roofing material for piles
When reinforcing the dressing will be created, begin to pour concrete solution, then wait 5-7 days before its fully cured.
After piles are created,move on to creating gratings. The first thing to hammer together wooden formwork, what would the width of the future Foundation was not less than 40 cm (and then 50).Later in the formwork stacked valve rods, tying them with wire to the valve, sticking the piles.
When the steel frame will be created, proceed to the creation of strip Foundation: concrete solution, get to grips, and bring down the formwork.
Formwork for pile-strip Foundation
To read details about the creation strip Foundation in the corresponding article, where more detailed process.
The pile-strip Foundation
It should be noted, that process of making a pile Foundation with a grillage similar, the difference is, that raft would be at the height of 30-50 cm from the ground, not giving her a load. This option is not always satisfied gardeners, because. too much conspicuous gap between the ground and the building, although it can be nice to close plastic.
As you can see, the construction of a pile-strip Foundation also is not anything complicated. The creation of this Foundation helps to save on building materials (ready piles are more expensive), and does not require involvement of special equipment, so is ideal for suburban areas.
Types of Pile
Pile foundations are a type of deep foundation that need to be used if the load bearing capacity of the surface strata (soil, earth etc….) is poor.
Foundations are typically considered deep when they need to extend beyond 3m below the finished ground level. As a point of note, deep foundations differ from shallow foundations which include strip foundations, pad foundations and raft foundations.
Piles are generally used to spread the load of a building through soft and/or unstable ground, to firmer ground further down. Piles are usually made of concrete, either precast or poured in-situ on site.
In domestic housing situations the concrete or steel piles are joined at the top with a reinforced concrete beam, commonly called a ring beam. The ring beam sits on top of the piles and allows the superstructure, I.E. Brickwork and/or Blockwork to be built or stabilised.
Pile foundation with piles and reinforced ring beam
Piled Foundations are used for either economic or structural reasons, when it is necessary to transfer the load to a deeper more stable area of ground. When the load cannot be supported by shallow foundations then piles can be used.
They are also used to anchor structures that are ly to be lifted or pushed over, such as chimneys and other tall constructions. Piles are needed where the lateral force on the building needs to be anchored to stop the building falling over sideways.
The two Types of Pile Construction
Essentially there are two types of pile:
- Replacement piles: These are piles which are put into holes dug or augured the earth. The concrete, or steel, simply replaces the earth, clay etc…. which has been excavated.
- Displacement piles: These are precast or pre-formed piles which are driven into the ground by a huge piling hammer. These displace the earth they are driven through.
When choosing a piling system for foundation use there are 4 main things to base a decision on.
- The load (or weight) of the building or structure to be supported
- The Cost of piling versus other foundation types
- The physical possibilities of getting very heavy piling equipment to the site without causing more disruption such as noise or further instability to a structure etc…. than necessary
- The condition of the ground and surrounding strata
Piling is being used more often these days than in past years. This is largely because of the huge increases in cost of carting away the many tonnes of soil required for a normal strip or raft foundation.
The closer together piles are placed, the less the diameter of each pile needs to be and in some cases, especially in situations where a lot of subsidence has occurred, piles can be drilled through existing floor slabs to stop them sinking any further. This type of piling is called mini piling.
Micro piles, usually even smaller diameters, are used where access is very much restricted. Piles can also be used when underpinning a property that may be suffering from subsidence issues or other issues that have caused instability.
Understanding the Types of Pile
There are a number of different piles that are used in different circumstances. Which is used will depend of the ground conditions at all levels and the type of the structure to be supported.
Here are a number of the most common pile types explained so that you can understand the considerations involved in the selection in a particular type of pile:
End Bearing Pile
These are piles that transfer the load of the building through the soft, compressible strata or soil at the surface to the harder bedrock below it. With end bearing piles the stability of the foundations is achieved by creating a secure footing into the solid, uncompressible strata, which is usually the bedrock under the loose soil.
End bearing pile going through soft soil and embedding in harder soil
These are very common types of pile, and generally the most easily understood.
Friction PilesWhere is in not possible, either economically or physically to use an end bearing pile, another alternative can be used; a friction pile.
Friction pile going through increasingly stiffening soil
There are two forces at work here – As the pile is driven into deeper soil, the soil is compacted and offers great strength which offers some of the end bearing, load carrying capacity of the straight forward end bearing pile.
However, this alone is not enough. There is extra load bearing capacity derived from the friction of the pile in the soil that it is in contact with – much a nail driven into a piece of wood that becomes more secure and held fast the further that it is driven in.
Settlement Reducing Piles
These are piles that are designed to offer stability against settlement and subsidence.
Settlement reducing piles supporting sagging foundation
They are generally used in conjunction with other foundation types, such as the raft foundation, to offer more stability. They reduce the sagging effect in the centre of foundations by reinforcing the soil below and creating leverage which counters the sagging movement.
These are piles that are used to provide stability to tall structures by anchoring them firmly into the ground. The pile will counter act the lateral forces that the building will experience from such forces as wind etc….
Factors Affecting the Type of Piles Used
The main factors that determine which type of pile will be used is as follows:
Location of the Pile and the Structure it will Support
For structures that will be over water (such as jetties, piers, and wharfs) driven displacement piles are the best solution. When it comes to using them on land there are other considerations to take in to account.
Displacement piles are generally the most cost effective but cannot always be used as driving them in will cause vibrations that will affect surrounding buildings. In these situations bored replacement piles are typically used.
For large structures, where large diameter piles are going to be needed, it is often cheaper to bore the piles into place.When piles are required for existing structures then jack piles are generally used. These are piles which are inserted by excavating the existing foundations and then adding sections of the pile under the building that are then pushed down into place using powerful jacks that drive each section into the ground.
Inserting piles below a foundation using a powerful jack
Cost of Adding Piles
Cost is always an important consideration in any building project and especially so when you are involved with piling. The main costs that need to be considered are:
- Cost of the materials use in the piles
- The time taken to build the piles
- The effect of the chosen piles on the cost of the building to be constructed above them
- Cost of excavations and preparing the site for the piles
- The specialist contractors costs; engineers to design and load test, levels of skills required to construct and build the piles
Designing Piles and the Specifications
These are general guidelines followed by professional in the construction industry that are required for pile foundations.
The foundations should be designed in accordance to the Eurocodes, especially BS EN 1997-1 and specifically for the design of concrete structures BS EN1992-1-1.
When making piles, the concrete needs to adhere to BS 8500-1. More information can be found in the BRE Special Digest SD1 which can be purchased from the Buildings Research Establishment: projects.bre.co.uk/sd1/wheretobuy.html.
Designing and constructing piles is a specialist task that involves a great deal of knowledge in ground types, material types, load calculations etc…. so we would always recommend that you consult with a structural engineer or piling specialist.