Anyone who has dug footings for the first time discovers the same thing. The heap beside the trench is visibly bigger than the trench, and it keeps growing. Groundworks spoil is the part of an extension that most consistently blows the waste budget, because people size the skips against the drawing rather than against what actually comes out. Our Knowsley skip hire service handles a steady run of extension work across the borough.
Why the heap is bigger than the hole
Ground that has been sitting undisturbed for thousands of years is compacted. Dig it out and you break that structure up, air gets into it, and the same material now occupies noticeably more space than it did in the ground.
That expansion is real and it is significant. Excavated clay and subsoil take up meaningfully more volume loose than they did in situ, and wet clay lumps up rather than flowing, which makes it worse. So the trench volume from the drawing is the minimum you will be moving, not the amount.
Around this area the ground is generally heavy, and heavy ground swells more and holds more water than sandy ground does. It also means everything you dig out in a wet spell is carrying water weight on top of everything else.
Working out roughly what you are dealing with
The arithmetic is simple enough. Length by width by depth of the trench gives you the in situ volume. Add a substantial allowance on top for the swell. Then remember that footings are rarely the only excavation on an extension, because there is usually an oversite dig, drainage runs and often a soakaway as well.
Then apply the weight test rather than the volume test. Soil and clay are dense, and a skip taking them will reach its legal limit while looking barely used. Our page on how full can you fill a skip with soil goes into what that means in practice, and our guide to skip size versus weight limits explains the two limits.
The counterintuitive conclusion is the same one that applies to any heavy load. Smaller containers exchanged more often move more material than one large container that cannot be lifted once it is full. A 4 tonne midi skip on a regular exchange is usually the efficient answer on a footings dig.
Separate the topsoil before anything else moves
The first few hundred millimetres of any dig is topsoil, and it is the most valuable material on the site. Below that is subsoil and clay, which is not.
Once those two are mixed in a single heap, you have turned something useful into something you are paying to remove. Strip the topsoil separately at the start, put it somewhere out of the way, and use it later for making good around the finished extension or for raising beds elsewhere in the garden.
Almost every extension needs soil bringing back in at the landscaping stage, so any you keep is soil you do not buy twice. Where the site does not produce enough, we can deliver screened top soil at that stage rather than you arranging it separately.
Skips or muck away
There is a point at which skips stop being the right tool. On a large dig, or where the excavation is happening over a day or two with a machine on site, a grab lorry or a tipper taking the material away in bulk is faster and often cheaper than a series of skip exchanges.
The deciding factors are usually access and volume. If a lorry can get to the heap and the quantity is substantial, bulk removal wins. If the site is tight, the dig is happening by hand or in stages, or the spoil has to be barrowed out through a narrow side access, skips are the practical answer.
Talk to us before the machine arrives rather than after. We would rather tell you that skips are the wrong answer for your particular job than sell you eight of them.
The later phases produce different waste
Spoil is only the first stage. Once the footings are in, an extension produces broken concrete and blockwork offcuts, then timber and packaging through the shell stage, then plasterboard and insulation at the fit out.
Those streams want different containers at different times. Plasterboard in particular has to be kept out of the general load, which our page on plasterboard disposal and building waste separation explains. Clean inert material from the groundworks phase gets crushed and recovered, and our environmental and recycling page covers what happens to it.
Access and placement on a live building site
The skip position on an extension needs thinking about for the whole programme, not just the dig. The obvious spot at the start is frequently where the materials need to be stacked a fortnight later, or where the mixer is going.
The other constraint is ground condition. A driveway that carried a loaded skip in March can be a different proposition once a mini digger has been over it a few times. Our drivers carry boards and will use them, but tell us if the surface is something you care about.
Local coverage
We work across this area from our own yard, running Maghull skip hire and Aintree skip hire jobs alongside Knowsley.
Ring us on 0151 909 6399 with the footprint of the extension and the footing depth, and we will tell you what to expect rather than leaving you to find out on the second day. Our contact page works if your builder would rather deal with us directly.
