Formwork, Access, and Line Pump Setup
Getting site-ready for a concrete pour vastly increases the chances of that pour being successful. By the time wet concrete hits your shuttering it’s too late; you’re managing thousands of kilograms of fluid pressure that offers no second chances. If a timber brace buckles, access is blocked by an overhanging bough, or the pump line kinks across an unprotected lawn, the job has to stop while the clock keeps ticking.
Unlike drum mixers that carry pre-batched concrete ticking toward its initial set through morning traffic on the A421 or M1, the volumetric concrete delivered by Custom Concrete is mixed fresh on your site. The dry materials stay separate until they hit the mixing auger. This removes the panic of a ‘hot load’ setting in the drum, but nevertheless, your site still has to be physically prepared to receive, pump, and hold that material without unnecessary problems.
1. Truck Access and Site Clearance
Before booking a pour, check that an eight-wheel volumetric mixer can physically reach your drop point. In rural Buckinghamshire lanes, Bedfordshire villages, or dense Hertfordshire suburbs, tight access is the primary reason pours have problems.
Specification | Site Requirement | Why It Matters | |
Gross Vehicle Weight | Up to 32 Tonnes | Solid tarmac, concrete, or compacted Type 1 MOT | Domestic block paving, uncompacted gravel, and flagstones will crack or rut under axle weight. |
Width Clearance | 3.0 Metres Minimum | Clear gateways, gateposts, and scaffolding | Mirrors and wheel arches need clearance; narrow piers leave no room for correction. |
Height Clearance | 4.0 Metres Minimum | Cut back branches; check low telephone/power cables | The mixer body sits high, and skip hoppers need overhead clearance to operate safely. |
Direct Chute Reach | 3.0 to 4.0 Metres | Drop area directly behind vehicle footprint | Direct discharge requires the truck to reverse square to the target footing or slab. |
Turning Radius | 12.5 Metres | Clear street parking opposite the entrance | An eight-wheeler cannot pivot tightly into a driveway without sweeping the opposite verge or kerb. |
2. Shuttering and Ground Conditions
Wet concrete weighs roughly 2,400 kg per cubic metre. It behaves like a dense hydraulic fluid, which creates continuous pressure outward against your timber shutters before curing begins. If you skimp on timber thickness, ignore ground conditions, or set levels poorly you won’t get the structural integrity and finish you need for your slab.
- Timber Selection – Use a minimum of 25mm (1 inch) thick sawn timber or 18mm exterior-grade structural plywood. Standard 12mm cladding or gravel boards will flex under pressure, leaving you with wavy edges along your finished slab.
- Peg Dimensions and Depth – Drive 50x50mm timber pegs at least 300mm to 450mm into firm, undisturbed subsoil. Space them no further than 600mm apart along the entire perimeter.
- Brace the Bottom Third – Pressure is greatest at the base of the shutter. Nail diagonal kickers angled at 45 degrees from the outer pegs directly into the bottom third of the shutter boards to resist outward blowouts.
- Sub-Base and Membrane – Compact a minimum 100mm layer of Type 1 MOT hardcore using a vibrating plate. Blind the compacted stone with a thin layer of sharp sand to cover sharp aggregate points, then roll out 1200-gauge DPM (damp-proof membrane). Overlap all joins by 300mm and seal with waterproof tape to stop puncture tears and leaks.
- Ground Temperature and Moisture Control – Never place concrete over frozen subgrade or frost. Cold ground stalls hydration and causes permanent surface delamination when the ground eventually thaws. Dry summer ground acts like a sucks mixing water out of the bottom of the slab before cement crystals can knit. If working over dry hardcore, mist the subgrade lightly with a hose before the pour. Damp it, but don’t leave any puddles.
3. Routing and Setting Up a Ground Line Pump
If your slab or footings are more than 25 metres from the road, or you need to navigate around tight building corners, or your access is through a domestic property, don’t even consider using wheelbarrows. Our line pump hire service bypasses the access obstacle and places the mix directly into the trench.
1. Establish the Pump Hardstanding
The line pump needs level hardstanding next to or behind the volumetric mixer. Allow a combined operational length of roughly 15 to 18 metres on the road or driveway for both vehicles to work together.
2. Map the Pipeline Run
Lay heavy-duty 4-inch steel delivery pipes and flexible rubber hoses along the shortest path. Keep the line as straight as possible. Every 90-degree bend adds friction, slows down the discharge speed, and increases line pressure.
3. Protect Lawns and Finished Surfaces
Line pumps pulse under hydraulic pressure. Lay timber scaffolding boards beneath the pipe couplings where they cross lawns, flowerbeds, or finished block paving to stop pipe whip from bruising turf or chipping stone.
4. Prepare the Slurry Primer
Before concrete enters the pipe, the line must be lubricated with a cement grout slurry or specialised priming compound to prevent aggregate bridging and blockages. Have a couple of bags of basic cement on hand if requested by the pump operator.
5. Build an On-Site Washout Station
Environmental regulations don’t allow washing concrete slurry into roadside gullies, storm drains, or soakaways. You’ll need to create a washout station – this is a heavy-duty builder’s bulk bag lined with a sheet of heavy polythene, or a small timber bund lined with plastic. The operator will discharge hopper remnants and wash down equipment safely inside this area.
4. Volumetric Concrete Benefits – Precision and Slump Control
Traditional drum deliveries force you to commit to an exact volume and slump when placing the order. If your ground worker dug a footing 50mm wider than planned across a 20-metre run, you end up short and facing costly part-load charges for a second truck. Volumetric concrete solves this directly at the chute.
- Pay For What You Lay – Dry aggregates, sand, water, and cement stay unmixed in separate onboard hoppers. When the pour starts, the mixer calibrates and batches on-site. When the shuttering fills, the operator stops the auger. You pay only for the exact cubic meterage placed. Check your trench, slab, or pad dimensions in the Custom Concrete Calculator beforehand to establish your baseline estimate.
- Slump Control Mid-Pour – Different parts of a build demand different workabilities. If you are casting a sloping trench footing, you need a stiffer, low-slump mix (S1 or S2) that stays where it is placed. If the pour then changes to a line-pumped floor slab, the operator dials up the water-to-cement ratio right at the control panel to deliver a fluid S3 or S4 slump – without weakening the structural grade.
- No Hot Loads – Drum mixers on long hauls can experience premature curing. Volumetric delivery guarantees that the water touches the cement only seconds before the concrete enters your forms.
A smooth, successful pour comes down to 30 minutes of detailed site prep. Check your clearances, double-brace your shuttering, map your pump line, and let the mixer handle the exact batching on the day.
Get the Site Ready, Negate the Risk
Wet concrete is a hard taskmaster, exerting relentless hydraulic pressure that exposes any lack of prep with formwork or access. Taking time to walk the pump route, lay scaffold boards across finished paving, and check overhead line clearances protects your build from expensive problems. With a volumetric setup, you only pay for the concrete that enters the forms – make sure those forms are rigid, pinned, and ready to hold it.
Ready to plan your pour?
Check your footing, slab, or trench dimensions with our Custom Concrete Calculator to calculate your baseline volume. If your drop point is over 25 metres from the road or tucked behind the property, speak to our team on 01582 861 899 to arrange Concrete Pump Hire alongside your volumetric delivery.