1. Preliminary works

Excavation is among the first jobs to be undertaken when starting the construction of any building, including a family home. Preliminary works, which are carried out before the actual construction work begins, include: staking out the construction area, i.e. marking the outline of the future building, erecting a fence around the building site, and making sure that the site is protected and secure. Excavation also falls into this category – marking out and excavating an access road (if there isn’t one already) and the excavation of construction pits, piling holes, trenches for the installation of services, basements, swimming pools, septic tanks, and boreholes for water. Each of these jobs must be set out in the planning documentation, on the basis of which planning permission is obtained.

2. Where and how to find contractors

Excavation involves removing earth to form a cavity in the ground. The earth and debris that has been removed is then set aside in a specific place on the building site so it can be used later for other works, or it is taken away to a landfill. Excavation creates the necessary space for construction work to begin on infrastructure or building projects. If you’ve decided to build a house and have already embarked on the venture, you’ll know that excavation work cannot be carried out without heavy machinery and construction equipment and tools. If you’ve opted for a turnkey project, then you won’t have to worry about hiring a contractor to carry out the excavation work. However, if you’re building your home in phases, then renting heavy machinery and construction equipment will be something you’ll have to think about.

Considering how many companies there are on the market that specialise in excavation work, it won’t be an easy decision for you to make unless you yourself are involved in the building industry and/or you’re armed with accurate information. Therefore, we’d definitely recommend you contact us, since we only work with reliable companies and contractors whose references can be found on our website along with all the comments from their previous clients. Complete the online form with some basic information about your project and interested contractors will soon get back to you with detailed quotes.

3. Geotechnical survey

A geotechnical survey is actually a document that reports on soil consistency and structure, as well as groundwater levels and recommendations for the technical project. It needs to be completed before any work can begin and has to be submitted as part of one’s planning application. More importantly, though, without it, calculations related to the foundations, excavation and construction pit protection, wastewater disposal, etc. cannot be performed. This study analyses the ground bearing capacity and the composition of the soil on the land you have purchased, and also what type of construction is possible if any. In addition, it determines the presence of groundwater, which is particularly important when it comes to water pumps and drinking water wells. The survey is compiled by a geotechnical engineer, who drills boreholes and performs various analyses. By analysing various factors and parameters, they assess the land and give recommendations, providing relevant and critical design guidance, which planners use when deciding on the type of foundations, building structure, load, and load capacity. The report also recommends whether excavation should be carried out, and if so what type, or whether filling is advisable.

4. Types of excavation

The type of excavation depends on the nature of the project - infrastructure or a building. Excavated earth and debris can be used for topsoil, fill, levelling the terrain, building paths or roads, and the foundations themselves. 

Surface excavation and deep excavation differ, as the names suggest, is the depth of the pit and also the purpose. Any type of excavation, i.e. how it is done, what type of machinery and tools are used, is determined by the intended purpose of the structure being built. Earth is categorized according to soil type. However, in more simple terms, it is usually loose, hard, or rocky, and each of these types requires a different approach, using different machinery and, certainly, the price will always depend on the complexity and scope of work.

Excavations are divided into two main groups – wide-area and narrow-area, including:

• excavations for foundations and concreting,
• excavations for installing services, sewer lines, plumbing, and manholes,
• excavations for drainage channels,
• excavations for swimming pools, basements, 
• excavation of construction pits,
• clearing and levelling terrain,
• strengthening and securing excavations with retaining or breast walls, and
• horizontal drilling in order to install services under roads and the like.

Additionally, once complete, the excavated area needs protecting against collapse, slips, and cave-ins, which also requires special material and equipment.

4.1. Wide-area excavations

The most common example of a wide-area excavation is a construction pit that is needed when a building requires space below ground level; this is usually a basement in a house, or an underground garage, a plant room, or service areas in public and commercial buildings.

Wide-area excavations are carried out using heavy machinery, such as bulldozers, excavators, dozers, and wheel tractor-scrapers. Excavation of soil is carried out in layers: a shallower layer at 0.2-0.4 m and a deeper one at 0.6-0.8 m. Rough excavation work ends at a level 0.2-0.3 m above the projected depth of the pit bottom and the next phase begins with the next stage of construction works.

If, after excavation, it is necessary to install a subbase or to compact and consolidate the earth, loaders, dumpers, excavators, and scrapers are used, since it is done gradually, layer by layer. Small amounts of a mixture of soil and aggregate are used as fill - 0.2-0.4 m if fine-grained or 0.3-0.7 m if coarse-grained. The spreading and rough grading of the soil is also performed by excavators or scrapers, with finish grading carried out by graders at the end.

4.2. Narrow-area excavations

When a new building is planned between existing buildings, building land will be limited. Hence, a narrower and deeper construction pit must be dug with vertical supports. Of course, this also requires accurate calculations and precise planning. In this case, too, compaction and consolidation of the bottom of the pit, a subbase, and protection are usually needed. The only differences in relation to wide-area excavations are firstly, that utility connections and service distribution lines are shorter, which means great care must be taken when it comes to existing pipes and lines in order not to damage them, and secondly, that debris is usually taken to landfill immediately rather than being left on site for later use.

5. Excavations for civil projects

Building an access road to your future property, a driveway to the garage, and later, garden paths all requires some kind of excavation work. These must all be routed and marked out, and then the terrain stabilized and a strong subbase laid before they are tarmacked or paved.

This type of excavation work also includes drilling boreholes for water and heat pump wells, horizontal drilling under roads for utility connections, and digging pits for swimming pools, septic tanks, and rainwater tanks. Various types of trenches and channels for the laying down of utility lines and pipes, storm drains, manholes, and, possibly, flood defences also need excavating.

6. Excavations for various types of services

Of course, before any work can begin, access needs to be secured for the machinery that will operate on the building site. In addition to excavation of the construction pit for the foundation slab or drilling and digging out for pad or strip foundations, there is also trenching for all types of lines and pipes (electrical, water, sewage), channels for foundation drainage and retaining and breast walls, and, finally, if necessary, those for telephone, television, and the Internet.

Some of this excavation work is carried out within the framework of preliminary works, some by specialist trades during building work, and some at the end when landscaping the exterior. However, whenever this work takes place and whatever its purpose, it must be well planned and carried out expertly and professionally to make sure problems are avoided altogether or, even worse, exacerbated. You must bear in mind that, regardless of the size of the project and the investment, the stability, longevity, and usability of your future home depends on how well this first phase of construction is carried out. Rectifying any resulting problems at a later date will involve great expense and an even greater headache.