Ben’s self-build story: laying a beam and block floor
This time, we’re back on site at House Planning Help founder Ben Adam-Smith’s self-build to see how work is progressing. Let’s find out what’s involved in laying a beam and block floor.
In the previous post, we followed the early stages of Ben’s build and saw his contractor successfully install a concrete strip foundation.
When we left the story, the strip foundations had been poured and set, and the rest of the plot levelled. We were ready for the ground floor of Ben’s 226 sqm Passivhaus in Hertfordshire to be laid.
In order to meet Passivhaus standard cost-effectively, Ben’s house is being built using familiar, tried-and-tested methods. And that mindset continues with the chosen approach to the floor.
Ben's architecture firm Parsons and Whittley have specified a beam and block floor for this project. But what is a beam and block floor exactly, and why was it the right choice for this build?
What is a beam and block floor?
At the start of the millennium, solid concrete slabs were still the preferred method for ground floors in most houses. Today, things are different, and most are built in the beam and block style.
First, dwarf (small) walls are built to support a large number of cast concrete beams. At this stage, drainage and service pipes are also fitted into the floor voids. Next, the concrete beams are carefully arranged across the full floor area of the house. And finally, a bit like a jumbo jigsaw puzzle, concrete blocks are dropped in to fill in the gaps.
There are significant benefits to using beam and block. “It’s a cost-effective technique and it doesn’t come with the risk of settlement, which a full ground-bearing slab can,” says Chris Parsons.
One potential challenge of using beam and block in a Passivhaus is that it does create a thermal bridge – in other words, areas where you could lose a lot of heat.
“We’ve done a lot of work to model the amount of heat that could be lost and put plans in place to include for that,” said Chris. “So it’s not a problem at all.”
The floor will not be completed for some time
While beam and block flooring is a straightforward job for experienced building contractors, some important adjustments do need to be made along the way. Where services enter the house, for example, blocks need to be cut to fit.
With all the beams and blocks dropped into place on Ben’s build, the team then brushed the floor with sand. The floor will remain at this relatively raw stage for the time being, as it gives the contractors an ideal, flat base to work from as they embark on the next stage of the build, constructing the first-floor walls. Later in the process, the floor will be carefully insulated and then a screed will be laid. The final flooring finish goes on top of this towards the end of the project.
“It’s an exciting time for us now,” said Ben. “The excavator and dumper have been sent packing and the site is piled high with towers of masonry and materials. Walking through it all is like being in Indiana Jones!”