Projects
Conservatory demolition and groundwork for house extension, case study
We were approached by a long term customer of ours, a builder and developer, to do the groundwork for a reasonable sized house extension in Towcester.
Objective
Our objective was to demolish the existing conservatory. Then to dig and pour footings for the new extension and do the masonry up to underside of block & beam. Then some foul and rainwater drainage, followed by installation of block & beam.
About the project
We started by removing the conservatory from site, and we removed this to a skip in our own yard, due to limited space on site. We we’re only able to get a 1.5 tonne digger in to this back garden through a narrow gap between the existing house and the standalone garage. There were a few steps here as well, so we put some plastic down on the steps and then laid type 1 MOT to form a ramp for the digger and to enable easier access for wheelbarrows back and forth. With the digger in the back garden, we started breaking out the floor of the conservatory. This came out easily enough, as it was only about 150mm thick, and not reinforced.
The footings were a bit more difficult to remove. At about a metre deep, which is a bit unusual for a conservatory, we had to break with the breaker attachment on the machine, then put the bucket on the machine and dig out what we’d broken. Then we had to put the breaker back on, then the bucket back on, and so on. We got the footing broken out in a bit over a day, and then we were ready to set out for the new footings.
The drawings asked for a 1-metre deep footing, but this is standard, and final depths were subject to the Building Inspector’s decision. There were a few small trees within 10 metres, and ordinarily any trees within 15 metres will have an effect on the footing depth, subject also to ground conditions of course. The Inspector asked for slightly deeper footings on two sides, to a depth of 1.4 metres, and then stepped back up to 1 metre on the final stretch.
We poured the footings to a depth that would enable 300mm of masonry to be laid to the underside of the beams (block & beam floor on this one). There was 8 cubic metres of concrete required in the footing, so we used a ‘line’ pump to get the concrete round the back of the house. We dug the oversite off to the required depth the next day, so that we had 250mm clearance underneath the block and beam floor.
With the masonry done, we filled the cavity to the required level, with Gen 1 concrete. Due to the available access, we had no choice but to carry the concrete beams round, one by one. These were laid within 2 days nonetheless, and the infill blocks and splits done thereafter. The floor was sealed with cement slurry, to complete the block and beam.
There was some drainage to complete for the project including foul and also rainwater from the new roof. The extension was generally for a new kitchen, so we laid new drainage from the proposed drainage points, to the existing foul manhole within the patio. We dug out for and laid underground rainwater pipes from the new downpipe positions. We had planned to dig out for and form a soakaway, but we discovered there was a dedicated surface water sewer in the Highway, and the existing rainwater pipes were connected to this system. We spoke to the Building Inspector, and he was fine for the new rainwater pipes to connect into this existing system, within the confines of the property.
With all of this work complete, we handed over to our customer, who continued with the build. It was good to carry out a small domestic job, and locally as well. A lot of our work is far from home and often on much bigger sites. Please contact us should you have a similar project you’d like help with.
