Part 1 of the Self-Build Guide: Laying the groundwork
Self-building and groundworks
The first chapter of this Self Build Guide is going to be looking at laying the foundations for your self-build, as the project finally commences and your new home begins to materialise. In due course we’ll be looking at the superstructure and roof, and other aspects of the construction process through to completion. We’re beginning with the laying the groundwork – the first stages of construction and aspects of the self-build that require excavation.
Ground-breaking exploits
If you’re embarking on the self-build route and constructing your own home, the safest and most reassuring solution is to engage a professional building company such as CB Homes. We offer a turnkey solution and in addition offer a great deal of added experience of the kinds of challenges a self-build project can encounter.
Surveying the scene for your new home
First of all, the site will have to be set out by a surveying engineer, according to the architect’s design. Years ago, this would have been set out using building lines and levels, and later levels and theodolite, but these days the equipment – still levels and theodolites – is digital. This has led to a high degree of accuracy and a very small allowance for human error when setting out.
The shape of the building, to its exact dimensions, will be set out by the engineer using profile boards and level readings. These often resemble wooden T-pieces. Benchmarks will be set up, to allow levels to be taken and compared across the site, so that all levels and lines of sight are included. There should be no ‘blind spots’ on the site where a level can’t be taken. These comparison levels can be taken above ground or below. For excavations, the levels will be below the benchmarks. This is an accurate way to ensure that the levels and height dimensions correspond to the plans. Interior wall foundations will be set out at this stage too.
In some cases, the digital information can be fed into the setting out equipment, in others the team will be working from plans. As well as levels, internal and external angles of the walls will be set out, to ensure the building is square. Details such as window levels and widths, doorways and other details will be added to the construction layout. Engineers will be on hand during the building process, to be involved in other groundwork, such as the setting out of drives or drainage. This may occur from the outset of the construction, or at a later date, depending on available access and scheduled timescales.
Laying a strong foundation
It is important to note that foundations are a relatively unknown entity before groundwork commences. Ground investigations give you an insight/snapshot into what will likely be under the ground but you never know until you start digging. It is always better to have a contingency in place for the foundations for a worse case scenario. Once you are out of the ground then there should be no hidden surprises.
Once the building has been set out, excavation can commence. The main types of foundations depend on the size and shape of the construction. They can basically be either strip (straight line trenches in the ground) or pile (vertical columns into the ground) or raft (a concrete slab spread out under the whole building or part of the building, supporting a number of columns or walls). The spoil can be retained on site for landscaping purposes later. If not, transport will need to be arranged to remove the spoil from site. For a new-build house, foundation depth will depend on factors such as ground conditions, soil type, load and proximity to trees.
Going underground for groundwork
At this point in the construction, the project may be delayed due to bad weather, especially heavy rains that results in the footings being flooding, or severe frost. It is always worth scheduling foundations to a period of dry weather as you always want to make these as effective as possible. The ideal scenario is to dig and pour concrete in the smallest time window as possible to ensure excavations are not left open for practical and Health and Safety measures.
As mentioned earlier, another possible delay is if the builder encounters something immovable, such as an underground obstruction like a well. Geo environmental surveys on many projects (if undertaken) will have been carried out in advance, in various degrees of detail. Sometimes ground type can fluctuate over small distances. Cheshire, for example, has shelves of red sandstone. If such an obstacle is found, the foundation design may require some amending, as rock is often strong enough to build off.
Building inspector visit at groundwork stage
If you have piling foundations, a specialist company will be appointed to undertake the entire foundation. These should be accredited and have all correct RAMS and H&S in place. If they are raft or trench foundations, the foundations themselves and any steelwork reinforcement to be included in them will have to be installed by specialist fitters and have structural designs and calculations. Once they are ready for the concrete pour, you’ll need to inform the local building inspector and warranty, who will visit the site to examine and pass them. Once they have been, you’ll be able to pour the ready-mix concrete. Depending on the size and scope of the building, this will be mixed to a specific strength, as detailed by your project structural engineer.
The foundation will give you a clear idea of the reality of the size of your project and a sense of the floorplan. Completing the groundwork is an exciting milestone on your self build journey. Once the concrete footings have set, the next stage will be the beginning of the substructure.
When building your own home, it is always better to have a professional company to oversee the foundations stage to minimise your exposure and unexpected costs. With CB Homes’ turnkey self-build solution, we provide a dedicated site manager and project management team so you have one direct point of contact throughout the entire construction process, keeping you informed of what’s happening every step of the way.
