Do-it-yourself pile-grillage foundation manufacturing technology

Any construction project must have a strong foundation in order to be stable and long-lasting. Combining the even support of a concrete beam grillage with the strength of concrete piles is one efficient technique known as the pile-grillage foundation. This technology offers dependable support for structures like sheds, homes, and small buildings, making it perfect for locations with varied soil conditions.

Because of the way the pile-grillage foundation is designed, there is less chance of settling or uneven stress on the soil because the weight of the structure is distributed evenly across several points. Because of this, it’s especially appropriate for locations where soil shifting is a possibility or where conventional foundations might not be able to offer enough support.

It’s crucial for anyone wishing to attempt this project on their own to comprehend the manufacturing procedure. It entails a number of crucial processes, including site preparation, load calculation, driving concrete piles, and grillage beam formation. This post will walk you through every step, providing helpful advice and pointers to guarantee a successful do-it-yourself pile-grillage foundation.

Step	Description
1	Prepare the site: clear the area and mark out the positions for piles.
2	Calculate the number and spacing of piles based on the load-bearing capacity needed.
3	Excavate holes for the piles, ensuring they reach below the frost line and are uniform in depth.
4	Insert piles (concrete or metal) into the excavated holes, ensuring they are vertical and aligned.
5	Pour concrete around the piles to secure them in place, allowing it to set.
6	Construct the grillage (a reinforced concrete beam) on top of the piles, ensuring it is level and provides adequate support.
7	Allow the entire foundation to cure and settle before further construction.

What is a pile-grillage foundation

A system of vertical supports, or piles, joined rigidly by an external load-bearing belt is called a pile-grillage foundation (see photo below).

The grillage supports the house’s walls, disperses the weight equally, and moves it to the pile system while the piles are positioned on thick soil layers.

This kind of foundation can be used in the most challenging situations, has a wide range of structural options, and can withstand a variety of loads. Piles of various kinds and compositions can be employed; the grillage can take the form of a robust strip of reinforced concrete or a straightforward support line.

It is possible to design a foundation with the required parameters that is best suited to the site’s hydrogeology, operating conditions, and current loads by combining these elements in different ways.

All pile foundation types can be categorized under this general category because they all typically have a grillage.

Existing types

The kind of piles used in a pile foundation determines its type.

There are:

• Rack piles. They are immersed in the ground until hard contact with dense soil layers appears. They form the strongest supporting structure and are capable of supporting buildings of any weight and number of storeys.
• Hanging piles. The load-bearing capacity of these supports depends on the friction force on the side walls and on the strength of the soil cushion under the tip, formed during immersion. This design is convenient when dense layers of soil are too deep, but can suddenly change its parameters due to changes in groundwater levels or other processes.

The substance used to create piles is:

• Wood. The most ancient and traditional material, which has many disadvantages. With the advent of other, more stable and durable types, wooden piles have practically disappeared from the arsenal of builders, although they are still used in some places (in private construction, for the construction of auxiliary buildings).
• Metal. Driven piles are not specially produced; in this role, pieces of rails, channels or I-beams of suitable size are used. Screw piles are manufactured completely ready for use. The specificity of the metal does not allow to obtain durable supports due to corrosion caused by electrochemical processes and the presence of stray currents.
• Reinforced concrete. The most common type of piles. The most durable are driven piles, manufactured using a special technology using prestressed reinforcement. Bored piles are cast from concrete directly on the site, which is convenient, reduces transportation costs and the overall level of use of construction equipment, but significantly increases the manufacturing time due to the need to cure the concrete to gain structural strength.

Three primary varieties of pile foundations exist:

• On driven piles. The immersion of the shafts is carried out by special machines. The process does not take much time, the supports are strong and reliable. The disadvantage is the impossibility of carrying out work near the buildings in use due to soil movements that occur during immersion.
• On bored piles. This type of piles is convenient because it does not require transportation, unloading, or the use of lifting equipment. A sleeve (a type of formwork made from roofing felt or plastic pipe of suitable diameter) is lowered into a pre-prepared well, a reinforcement cage is installed and concrete is poured. All operations can be performed independently, but a fairly long period of holding the piles will be required for the concrete to harden.
• On screw piles. They are made of steel pipes with a wall thickness of at least 4 mm. The lower part has a welded or cast pointed tip and spiral cutting blades. Driving screw piles resembles the process of screwing a screw – the blades provide immersion, the sharp tip pushes apart or splits the obstacles encountered. Screw piles can be installed manually, if necessary, they are removed and reused in other places. The service life depends only on the intensity of corrosion.

Types of grillages depending on the location

There are three types of grillage construction, which vary depending on the depth of immersion:

• Recessed. It is a complete analogue of the recessed strip foundation. Immersed to a depth below the freezing level to eliminate heaving loads directed vertically upward.In this case, the developed side surface of the wall experiences maximum values ​​of lateral loads, which must be taken into account when designing. It is not used on complex or waterlogged soils due to the lack of technological conditions for the production of concrete casting.
• Shallow. This is the most common design option for a pile-strip foundation, where the strip is immersed to a small (40-70 cm) depth. This option is much more economical than the buried one, since it does not require such a serious amount of excavation work.
• Non-buried. In this case, the grillage is installed above the ground surface, forming a gap of a certain height. This option is used on soils that do not allow for extensive excavation work – waterlogged, excessively loose, prone to heaving or seasonal movements.

Some experts distinguish between pile-tape and pile-grillage support structures based on whether the tape is buried in the ground or not. Others combine them into a single group because they are essentially the same in terms of general design.

Use Cases

There are various ways to use grillage material, including:

• Wood. Use either solid timber 150:200 or 200:200 mm, or a pack of edged boards 50:200, assembled in 3 or 4 layers. The resulting beam has high load-bearing capabilities and is easy to process and install. The cost of wood is relatively low, so a grillage of this type is the best option for houses that do not have a lot of weight (wood, aerated concrete, foam concrete).
• Metal. This type of grillage allows you to get a strong base, rigidly connected to the pile heads. The result is a durable structure, the installation time of which is the shortest, and the result is very reliable. A channel, I-beam or rail is used as beams; fastening to the tops of piles is carried out by welding. Most often used in combination with screw piles.
• Reinforced concrete. This type of grillage is built using the conventional technology of casting a monolithic strip (floor tile). The only difference arises from the presence of an air gap between the soil and the bottom of the base. In addition, the reinforcement of the piles must be rigidly connected to the reinforced belt of the tape, forming a monolithic supporting structure. This procedure forms a powerful and rigid base that is resistant to all types of loads. The disadvantage is the long hardening time of concrete, which stops work for a month.

Its required height

The type of material used for the house’s walls directly affects the height of the grillage. It is generally accepted that a house made of brick (concrete, cinder block) must be at least 15-20 cm above ground. The height of the grillage should be roughly 40–60 cm higher for wooden houses.

This will enable the wood to be isolated from moisture sources below and provide the required flexural rigidity.

This is referring to the snow cover, the height of which needs to be considered as well. In the event that the area experiences exceptionally snowy winters with tall snowdrifts, the height of the grillage that rises above their level must be determined.

Laying depth – what it depends on

The site’s soil conditions determine how deep to place objects.

Every relevant factor is considered:

• Groundwater level.
• Availability and volumes of soil water.
• Possibility of flooding in spring.
• The presence of seasonal changes in hydrogeology, an increase or decrease in the degree of filling of all aquifers.

It is frequently necessary to gather data from local meteorological and geological departments, speak with knowledgeable builders, and consult a variety of SNiP applications in order to determine the proper depth.

Please be aware that all values listed in different sources are minimum values; that is, while lifting height can be increased, gap height cannot be decreased.

Device

A supporting structure called the grillage is found beneath all load-bearing walls, internal and external.

It is put together into a single strip, and traditional technologies unique to this material are used to put the beams together into a single structure:

• Wooden beams are connected half-timber with a joint gasket with jute tape.
• Metal beams are welded to the ends with reinforced connections with threaded elements.
• The concrete grillage is cast in the form of a monolithic element, rigidly connected to the piles by a common reinforced belt.

Every beam has a fixed connection to every support beneath it. The spacing between them needs to match the size of the load; too much space will cause the beams to sag and distort all of the surrounding components. Beams may only be connected longitudinally above the pile head; joining them within the span is not permitted.

We go through the process of building a pile-grillage foundation step-by-step in this guide, providing homeowners who want to improve structural stability with useful advice and crucial pointers. From site preparation and material selection to concrete pouring and grillage beam securing, we offer clear instructions that enable you to effectively construct a long-lasting foundation for your building projects.

How to calculate a monolithic base

Specialists with experience and competence calculate the pile-grillage foundation.

This is an intricate and responsible engineering task that is too difficult for non-specialists or outsiders to complete (the work is done with the use of formulas and diagrams).

If you are unable to speak with experts, you can use online calculators, which provide a reasonably accurate response in a matter of seconds and at no cost at all.

The following actions should be taken if you must determine the supporting structure on your own for any reason::

• The weight of the house along with the property, wind and snow load, and additional elements is calculated. This point is the most difficult, since it is necessary to take into account absolutely all factors influencing the foundation from the side of the building. Some values ​​can be found in SNiP tables, for example, the magnitude of wind and snow loads characteristic of a given region.
• The resulting value is multiplied by the structural strength coefficient. Usually it is taken equal to 1.1, but in some cases an increased coefficient is used – 1.2.

The safety margin only applies to this particular house arrangement.

Its weight will increase with all extra components, furnishings, finishes, and additions, loading the foundation beyond the estimated amount.

Therefore, accepting a much higher strength coefficient is perfectly acceptable in order to prevent future foundation destruction or deformation.

The number of piles is calculated after the load has been established.

The entire weight of the house is divided by the unit’s allowable load, and the result is rounded to the nearest whole number.

The passport of products specifies the allowable load on ready-made supports; for brownish piles, this is determined independently using the SNiP or other sources’ methodology.

Step -by -step instructions for installation with your own hands

Take into consideration the process for installing reinforced concrete grillage—one of the trickiest options—at a height of 30 cm above the ground.

Method:

Preparation

The website is arranged and cleaned (if necessary). Eliminate any unnecessary items, vegetation, and other obstructions.

The site is being marked with the aid of pegs. One peg is installed on the support axis for driven piles, and the lines denoting the external and internal perimeters are marked for bored piles. They also call for the drilling of wells in preparation, which is done in accordance with the findings of test drilling.

In any case, it is done because it allows the length of the trunks to be determined and it determines the depth of dense soil layers.

Installation of piles

Specialized machines are used to drive piles.

A driving plan must be created to ensure that the completed piles do not obstruct the locations where the upcoming supports are to be installed.

Installation is typically done in a spiral or snake pattern, going from one place to another one after the other.

Wells are lined for bored piles by submerging a piece of plastic pipe with the necessary diameter or a pipe made of rolled roofing material. After that, an armored belt is put together and lowered into the well; the belt’s dimensions must be chosen so that the hole can be easily filled in.

In order for the reinforcement to be firmly attached to the grillage’s reinforced belt, its length needs to be greater than the well’s. After that, concrete is poured into the well, and it is left for the necessary 28 days.

Construction of formwork

It is not required to wait for the concrete in the wells to solidify before constructing formwork. When using driven piles, the construction process typically takes a week or so for the shaft to "suck," or restore the soil and firmly seal it to the side walls.

Formwork is a type of long wooden tray whose internal measurements mirror the grillage’s final shape.

To try to avoid gaps and cracks, the assembly is constructed from edged boards.

The formwork’s height ought to marginally surpass the grillage’s height. A number of supports are erected on the ground to give the lower section rigidity and to stop the formwork’s bottom from bending. Polyethylene covering the interior keeps material and/or water from leaking out of the formwork.

Creation of an armored belt

Conventional technology is used to create the reinforcement frame. Working rods are installed in the desired position in accordance with the design diagram and general guidelines, assisted by smooth auxiliary reinforcement.

The tight junction between the reinforced tape belt and the pile reinforcement—for which welding is the ideal method—is a crucial component. Soft wire is knitted to connect the remaining components.

Pouring concrete

After the concrete in the piles has fully solidified, concrete is poured.

This is crucial because uncured concrete can be distorted by the heavy weight of the reinforced concrete grillage.

To achieve a completely monolithic support with a high degree of rigidity, the pouring must be completed as fast as possible and without interruptions. For the first ten days, the concrete is leveled, covered with burlap or polyethylene, and watered sporadically.

The formwork is removed after ten days, and the tape is left in place until it has fully solidified, which happens twenty-eight days after pouring.

Floors on the ground

A grillage structure submerged in the ground is created using floors on the ground. Making a floor on the ground becomes excessively difficult, inefficient, and unfeasible if there is an air gap.

A layer of sand cushion covers the inner portion of the tape. After that, a layer of geotextile is applied, followed by a layer of crushed stone that is poured through yet another layer of geotextile.

The best outcome is obtained by gradually compacting the entire backfill. After that, a heat insulator is placed on top of a layer of screed.

Another screed is poured on top of it, and a heated floor system is installed inside.

This screed is ready for the finishing coat to be applied. Although the floor pie has many layers, it offers excellent heating and stops heat loss from coming into contact with the ground.

Waterproofing technology

One of the most widely used materials is used to waterproof the grillage:

• Hot bitumen.
• Bitumen mastic.
• Paping with roofing felt.
• Application of impregnating compounds.

Using bitumen mastic, which is readily available in ready-to-use form and flawlessly completes its tasks, is the easiest and fastest option. Apply with a brush or roller, typically in one or two coats.

Insulation scheme

Waterproof insulation materials are utilized:

• Liquid polyurethane foam.
• Extruded polystyrene foam (penoplex).
• Styrofoam.
• Expanded clay.
• Foam glass, etc.d.

Penoplex, which is glued in a thick layer to the entire surface of the grillage, both internal and external, is the most practical and efficient option.

A little worse, but far less expensive, is polystyrene foam, which is extremely brittle and crumbles easily. It is also highly resistant to moisture and heat.

Useful video

This section explains how to reinforce the grillage and how to create a pile-grillage base (a reinforced foundation) using only your hands.

Constructing a pile-grillage foundation on your own can be a satisfying undertaking, providing a sturdy foundation for constructions such as decks, small buildings, or additions. Through adherence to the detailed instructions provided in this guide, you have acquired the ability to efficiently plan, prepare, and carry out every phase.

First and foremost, it is essential to comprehend the load requirements and soil conditions unique to your site. With the appropriate modifications to pile depth and spacing, this foundation type is adaptable and can handle a variety of soil types. A stable structure is established by making certain that every pile is precisely aligned and securely fastened.

Second, great care and attention to detail are used in the construction of the grillage. Precision is essential for everything from assembling the reinforcement bars to pouring and leveling the concrete. This increases the foundation’s durability and load-bearing capacity by ensuring that the load is distributed evenly throughout it.

Finally, it’s critical to keep quality control throughout the entire process. Future issues are avoided by performing routine inspections of the overall structural integrity, concrete curing, and pile alignment. Following these recommendations will help to prolong the life of your foundation and create a strong foundation for any further building projects.

Video on the topic

Pile-grillage foundation. 1 part