Introduction of Rubble Trench Foundation
One of the most important and essential parts of any structure is its foundation. Foundation is the most crucial part which bears the total load of the structure.
There are essentially two main parts to any foundation of the structure, the footing, and the stem wall. The footing is the crucial part of the foundation which is underneath the soil line that goes at least as deep as the frost line for your region.
This will ensure that your structure is sitting on a solid foundation that won’t shift during the continuous freezing and thawing of the ground. The stem wall is the above-ground part of the foundation that raises your walls off of the ground to avoid direct contact with moisture.
In this article, you will get to know about the Rubble Trench Foundation, the step-by-step process of the rubble trench foundation, and the various advantages and disadvantages of a Rubble trench foundation.
What Is a Rubble Trench Foundation?
The Rubble trench foundation is basically a continuous trench footer that is around the structural perimeter. The trench foundation uniquely provides both structural bearing as well as proper water drainage.
Considering the winter season, the trenches are dug to the depth of the freezing point of the soil and filled with stone for structural stability. For the purpose of distributing the structural loads of the building, supported by a trench filled with stone.
This type of foundation system combines structural bearing and water drainage, which is rarely seen. The width of the trench determines its bearing capacity (as a footer made of standard concrete).
A liner made of filter fabric is placed between the clay and the stones so that the cracks between the stones are not filled with silt. Most foundation systems require drainage to prevent water from failing the foundation.
Water can damage the footer of a concrete foundation. The soil around your foundation swells during the winter months, causing it to slide upwards and then return to its original position when the soil melts.
Due to this heaving movement, this foundation is suitable for preventing structural damage or stabilizing uneven buildings. Using a rubble trench as a foundation footer is a cost-effective, environmentally friendly, and resource-efficient option.
It has been used in construction for thousands of years in various forms of the rubble trench foundation. In areas of the Middle East and Africa, earthen walls are constructed using slopes loaded with loose rocks. Because the ground never freezes, the ditches are only a few feet deep.
Rubble Trench Foundation
The Rubble trench foundation system was discovered by Frank Lloyd Wright around the turn of the twentieth century. As the water got fully drained, he noticed the composition to be “perfectly static” which indicated that there was no lugging.
The “drywall footing” became the standard method of construction for him from that point on. Numerous structures have stood the test of time thanks to the rubble trench.
The trench should extend around the entire perimeter of the building, covering all of the building’s external load-bearing points. When it comes to the foundation of a home, the amount of digging required is significantly less than if you were to lay a concrete slab, which necessitates much more digging.
According to the local frost-free depth, the minimum depth of the trench must be at least as deep as the trench. Because the temperature never drops below zero degrees Fahrenheit, any water that falls into the trench will not freeze.
For every 1 meter of the trench, the bottom of the trench should slope at least 3 cm to divert water toward a single point. Through an outlet to either daylight or a dry well, water can be diverted from the foundation.
Trench clogging is prevented by putting a geotextile in the trench to prevent soil from entering the trench and clogging its exit. For this foundation to work properly, all you really need is this geotextile. Without it, the trench may function for some time, but any silting will eventually reduce the trench’s ability to drain away water, making the rubble trench completely useless, with frost heaving just around the corner.
Between 2.5 to 5 centimeters in diameter, the trench is filled with an average of angular and cleaned stones using either pneumatic or hand-powered tamper. Before filling the trench, the crushed stone must be washed to remove sand and smaller particles that could clog the trench and/or outlet over time if they are not removed. A layer of crushed stone is tamper-tamped every 30 centimeters until the trench is about 20-30 centimeters below grade (ground surface). The stonework begins here.
It’s possible to build a formwork with a rebar inside and pour a concrete grade beam, which would greatly reduce the need for cement if you used the rubble trench. Using only the oldest building material known to man, stone, and RTF can be constructed without the use of a single drop of cement.
If you want to raise the house above the ground, you’ll need a continuous wall made of either large blocks of stone or smaller, more manageable stones arranged in a beautiful dry stacked stone wall (see below left).
Both options would give your home a more natural appearance than cement could, allowing it to truly blend in with the landscape. The foundation should be at least 40cm above the ground in order to protect the house from snow and water splashing.
Even though the rubble trench can handle the majority of the precipitation that one can expect, you should still add a small slope around your entire foundation. To begin with, this prevents much of the precipitation from making it into the trench in any case.
Allow the Geotextile to extend a few inches up the side of the foundation stones, and then fill the space between the stones and the Geotextile with earth. This prevents any additional earth from entering the trench, preventing clogging.
A slope of at least a meter away from the foundation should be shaped and compacted. In the right hands, this should leave you with a solid foundation that will serve you well for many years to come.
How to Build Rubble Trench Foundation?
Following is the step by step process of the Rubble Trench Foundation which is as follows
- Dig a trench that is at least 4 inches deep and slopes toward daylight or a dry well in order to keep the ground from freezing. One-eighth of a degree “Lines must be at least one foot long At the very least, I do at least 16.” Despite the fact that this trench is broad, the depth needed for support of structure depends on the carrying volume of soil and loads of building.
- The trench is to be stroked with a fabric of filter to keep silt from clogging the footer over time.
- You can tamp it with your hands if you want to add another 4 inches of stone. Maintain the drainage slope by placing the gravel fill under the line of frost.
- Lay a continuous pricked pipe of four inches on the crest of the sloping rock. The pipe should be sloping toward the light, like a typical foundation footer. As a technical side note, the drainpipe isn’t necessarily required as the whole rubble trench footer gives sewerage. Even though it serves no purpose, incorporating a drain pipe in a construction plan can make it easier to obtain building permission in some places.
- Use 1-1/2-inch gravel to fill the remainder of the trench, tamping after every vertical foot of fill. A stone the size of a grain of sand No need to utilize a pneumatic tamper in this case…hand tampers are sufficient. The tamper can be dropped over the entire trench as you go down it. To ensure that the bearing remains stable throughout time, it is necessary to tame the stones.
- Stone or broken concrete rubble fill can be used, but it must be cleansed of fines, and it should have an average diameter between 1 and 1.5 inches, with at least 1/4-inch in diameter. Rubble trenches can become clogged with fine dust or sand-sized particles, preventing them from draining correctly. A hose can be used to check the drainage in your trench before you go any further.
- The formwork required for the grade beam can be coated with biodegradable oil. This ensures that your form may be easily released for future usage. Vegetable oil of any kind will do the trick. 2×12’s are used to make the grade beam and then used to build structural framing when the beam has hardened. For a grade beam or thicker perimeter beam, set the formwork.
- Concrete will almost certainly require a steel reinforcing bar (rebar). Grade beams need to be structurally sound. A single concrete pour is all that is needed to install a thickened perimeter beam over the rubble trench and a slab-on-grade with a thickened perimeter beam.
- Pour a concrete grade beam at this point. A slab-on-grade foundation’s thickened perimeter can incorporate the grade beam, or it can be used as a separate structural member all the way around the building’s perimeter (as this photo shows).
- When it comes to constructing a home’s structural framework, the options are nearly limitless, from a stem wall and crawl space to full basements, stud walls, or post-and-beam structures. All structural elements should be sized by an engineer. Note that Rebar is still protruding from the ground to support the wood shape until the concrete has hardened.
Benefits of Rubble Trench Foundation
The Trench Foundation has various benefits, which are as follows:
- Not so expensive – Compared to a standard concrete footing, less effort and less material are needed before the rubble foundation. Over-digging, footer formation, and backfill are all omitted.
- Because the excavation is restricted to the building’s outline, there will be as little disruption to the surrounding area as possible.
- Rubble trench footers require around 80% less concrete than the standard footer would (which depends upon the depth of the frost and the foundation type inducted). For every pound of cement used in the mix, 1.25 pounds of greenhouse gas emissions are generated. Concrete production is a major source of these emissions. The use of less concrete reduces emissions of greenhouse gases.
- As long as the fine particles are cleaned off, recycled crushed concrete can be used as a rubble fill.
- Many natural builders prefer to use rubble trench foundations because they save money, time, labor, and the need for cement and rebar. This type of foundation also improves drainage. There is no need for cement or rebar if you don’t want to use them.
- Drainage and appropriate load distribution are two of the most important aspects of a successful foundation. The footer remains dry at all times thanks to the rubble trench that allows complete water sewerage below the structure of foundation carrying elements.
- Using a static foundation system like this one assures that water will not freeze beneath the structure. It is possible for a building foundation to be heaved when groundwater freezes.
- To avoid frost heaving, a foundation in a temperate climate must be designed to prevent water from accumulating beneath the foundation walls. 6. The Frozen Landscape Water in the ground freezes and expands, causing the ground to rise up with it. In the spring, the ground thaws and the water evaporates, causing the ground to sink anew.
- The home will twist and skew as a result of the repeated pressing up and down, which could cause structural difficulties and make it difficult to open and close doors and windows. By using a drainage trench filled with crushed stone that drains water away from the foundation, the Rubble Trench Foundation overcomes these difficulties.
- However, it wasn’t until the 20th century that American architect Frank Lloyd Wright adopted this technique (which he named “drywall footing”) in his architectural designs.
Also Read: Types of Beams in Constructions
Rubble Trench Foundation Cost
The construction of the Rubble trench foundation cost is relatively lower due to the less labor required, the lesser material required. In the construction of the Rubble trench foundation cost required is lesser than the conventional concrete footing.
In the Rubble foundation, there will be no over-digging, no footer or backfill is required.
Advantages of Rubble Trench Foundation:
The various advantages of the Rubble Trench foundation are as follows:
- Cheaper than the other options.
- Environmentally friendly.
- Allows for excellent soil drainage. Due to its resistance to moisture, groundwater will not harm the stone.
- The rubble used in this type of foundation is extremely strong and durable, making it an excellent choice.
- Suitable for all climates and all-weather.
Disadvantages of Rubble Trench Foundation:
There are also some disadvantages of Rubble trench foundation which are as follows
- There are a variety of footing alternatives for soils with low bearing capability, such as digging a very long trench.
- Since building codes do not specifically mention rubble trench foundations, it is possible that.
Conclusion of Rubble Trench Foundation:
A building’s foundation is responsible for distributing the weight of the structure above it equally on the ground below. There are a number of factors to consider when choosing a foundation for a building, which include its dimensions and appearance, the structural system form it uses, its slope and how much weight it can bear, and the depth of winter ground freezes.
Rubble trenches are an inexpensive influence method of building the building footer, that is generally located below ground level. It has been employed in construction for thousands of years in various versions of the rubble trench foundation.
The rubble trench foundation technique was discovered in the early 1900s by Frank Lloyd Wright. This is because the structures were “absolutely still,” showing no symptoms of heaving, according to him. The “drywall footing” became his standard method of construction from that point on.
This type of foundation uses a continuous trench filled with crushed stone, and a grade beam on top of it to ensure a solid foundation. When a damp proof course is required in concrete, this foundation is the only one that can offer both structural support and water drainage in a single system. Water tends to seep into the foundation, especially during the rainy season.
Because water can’t move freely through loosely packed rubble, it can’t generate moisture in the foundation by capillary action.
The water is then channeled beneath the loosely packed rubble in a channel. This channel runs the length of the foundation and is slightly slanted. There is a hole where all of the water from the deepest point is collected and drained away. Aquifers are created as a result of this water being injected into the ground.