If you are building an extension or a new home in Northamptonshire, the ground floor decision matters more than most people expect. Both a suspended beam and block floor and a ground-bearing concrete slab will do the job, but the right one depends on your soil, your site levels and your budget. Here is how we weigh it up on real jobs.
A ground-bearing concrete slab sits directly on a prepared and compacted sub-base, with insulation and a damp-proof membrane underneath. The ground carries the load, so it relies on the soil being stable and not too deep.
A beam and block floor is a suspended floor. Pre-stressed concrete beams span between the foundations, the gaps are filled with standard concrete blocks, and the whole thing bridges over the ground with a ventilated void below. The foundations carry the load, not the soil directly under the floor.
Around Northampton you find a real mix, from firm boulder clay to made-up ground on older plots and shrinkable clay near established trees. That variation is usually what settles the argument.
If we would need to dig out and import a deep stone build-up to reach good ground, a ground-bearing slab can get expensive and risky. A suspended beam and block floor often becomes the sensible choice because it spans across the weak ground instead of depending on it.
For a small, level extension on good ground, a ground-bearing slab is normally the lower-cost option and can be poured and finished by us in a couple of days once the dig is ready. There is less to crane in and less waiting on deliveries.
Beam and block typically costs more per square metre once you factor in the beams, blocks and grouting, but it can save money overall on a difficult site by cutting the amount of muck away and stone in. As a rough steer, expect beam and block to add somewhere in the region of 15 to 40 percent over a simple slab, depending on span and access.
Beam and block needs a properly ventilated void, so you will want air bricks and a clear gap below the beams. That void is also handy if you ever need to run services or deal with future ground movement.
A slab is unforgiving if levels are wrong, because it is set once it is poured. Both floors need good insulation to meet current Building Regulations, and both need a continuous damp-proof membrane tied into the wall DPC. Getting those details right at groundwork stage is far cheaper than fixing them later.
Both can be made equally warm because the insulation, not the structure, does the work. A ground-bearing slab can feel slightly more stable underfoot, while beam and block performs just as well once correctly insulated and finished.
Yes. Underfloor heating works well over both, usually with a screed on top of the insulation. We just need to know early so the floor build-up and levels are set correctly from the start.
It comes down to a look at your ground conditions, site levels and any nearby trees, ideally alongside your soil or trial hole information. We are happy to assess the site and give you an honest recommendation before any digging begins.
Tell us about the plot and we will come back with a free quote.
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