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Category: Ben’s self build blog

  • Ben’s self-build story: laying a beam and block floor

    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!”

     

  • Ben’s self-build story: what is a concrete strip foundation?

    Ben’s self-build story: what is a concrete strip foundation?

    After more than six years of research and planning, Ben Adam-Smith’s vision for a 226sqm Passivhaus is built on solid foundations. With a rollercoaster few years behind him, it’s a huge relief to be finally pouring the real thing.

     

    Like most first-time self builders, House Planning Help founder Ben Adam-Smith and his wife Kay have overcome stumbles and setbacks to get their ambitious plans for a Passivhaus off the ground. From a long and arduous plot search to being stunned by the sky-high bids from contractors, it’s not been the easiest ride.

    The good news is that their determination has paid off. After securing a beautiful rural half-acre plot in Hertfordshire back in 2016, they’re now putting their architect’s plans in the hands of their chosen contractor. Their dream home is about to get real.

    Plans for Ben’s Passivhaus were drawn up by Norfolk-based architecture firm Parsons and Whittley. An interesting element of their plans is that they don’t rely on rarefied building skills or unconventional and expensive materials.

    Instead, the house will be a traditional cavity wall masonry build, which is a common choice in the UK. The key difference will be the attention to detail that’s required by Ben’s building contractors.

    Cost-effective method

    “We wanted to build a Passivhaus because it would be cheap to run and would offer a really comfortable and healthy place to live,” says Ben. “When we first saw the return quotes from the contractors, we were surprised. We already had an efficient form and a cost-effective build method, but ultimately we had to make some compromises to bring the cost down. as well as pay more than our initial budget.”

    With contractors appointed and the site secured, the team has been busy getting the first few key stages of construction completed.

    First up was the precision job of pinpointing precisely where the house will sit on the plot. While this sounds a simple job in principle, it needs to be extremely precise – deviating by as little as 5mm from the approved plans.

    With that job done, and things getting off on a solid footing, it was time to build a genuinely solid footing in the form of foundations. Ben’s architecture firm specified a concrete strip foundation. But what exactly is that?

     

    What is a strip foundation?

    According to Chris Parsons from architects Parsons + Whittley, “strip foundations are how most houses have been built for the past 40 years. It’s a simple, traditional and cost-effective way of doing things.”

    The process involves digging out trenches around the perimeter of the house and along the line of all load-bearing walls. Concrete is then poured in until it reaches just below ground level.

    The site’s good sandy ground also made strip foundations a practical solution. Good ground conditions are important in strip foundations, because the sides of the trench play a big part in supporting the load.

    Rain, rain go away

    Heavy rain did slow the job down a little bit. Flooded trenches had to be pumped out before concrete could be poured, but overall this stage of construction passed without any nasty surprises.

    With the concrete foundations fully set and the rest of the earth levelled, it’s now deliveries rather than rain that are flooding the site. Ben’s team is ready to move on to the next stage of the build – laying a beam and block ground floor – and you can read all about what happened in our next post.