With all the prep work complete, we are ready for the concrete pour. The pump lorry arrived first thing this morning followed shortly after by the mixer lorry.
The pour goes well, but during the levelling out we learn that we are a bit short. The correct amount was ordered (7m³). We find out that we should have ordered and additional quantity of 0.25m³ as there is a residual amount of concrete that cannot be pumped out of the lorry. The difference is made up on site. Finally, the concrete is smoothed over with a power float and left to cure over the weekend. A small celebration as we’re out of the ground from here on (ignoring the back fill works to the retaining wall).
The extension area on the lower ground floor has been excavated this week. It has taken just a week to shift 50 tonnes. The photo above shows the excavated area, which is where the new kitchen (part) and stairs will be accommodated.The new pantry will also be in this area – so plenty of thermal mass to regulate the temperature, which is perfect for food storage, and perhaps a bit of home brewing!
On the left of the photo, the new retaining wall blocks are being used temporarily to prop the shuttering for the first section of underpinning along the side wall. The underpinning will continue next week.
The first block course has been laid on top of the ground bearing lintels. This course (highlighted in yellow in the section detail) will act as a shutter for the concrete slab pour. So, just a little more excavation to go and then the hardcore sub base can be laid in preparation for the lower ground floor slab.
The ground bearing lintels arrive: these will sit on top of the concrete pipes. They are huge: 290 x 100mm and 3.5m long, and incredibly heavy. Having perhaps sounded a little smug about the amount of concrete saved (in the previous post), I don’t think we will have saved much financially. These lintels are specials and have cost a small fortune!
The photo above shows the lintels in place. Two 100mm wide lintels are placed side-by-side, allowing the 200mm aerated concrete blocks to be built straight off the lintels. Hopefully we’ll be out of the ground soon.
We bury a scandalous amount of concrete in this country to prop up our buildings. I was keen to ensure that our structural engineer came up with a ‘creative solution’ to mitigate the amount needed, as we have had to go so deep to ensure we are below the level of the sewer. The concrete ‘pipes’ seems a good solution and getting hold of the steel ducts was a good find by the contractor. The picture above shows one of the four ducts for the founding ‘moulds’ placed in-situ ready for the concrete pour. In total, we need 2.5m³ of concrete as opposed to 8.75m³ with a traditional deep trench fill, a saving of 70% of grey stuff.
Yes, the rain came this week. 79mm fell here in 24 hours (Monday morning being the worst) – just perfect, absolutely perfect conditions to do anything other than dig the foundings for the new foundations! So, it has been slippy and sticky on site, which has meant slow progress. So not a huge amount to write about this week.
Not to despair, the guys have progressed as well as can be expected and have got the foundings prepared and ready for the first inspection by Building Control tomorrow (Friday). The concrete delivery is booked for the afternoon, immediately after the inspection sign off. So, all being well the foundations for the rear wall will be cast tomorrow. This is good as we’re expecting a dryish weekend before poor weather resumes next week.
In an attempt to minimise the amount of concrete in our extra deep (1.2m) foundations (see earlier posts related to Wessex Water requirements), the design adopted uses 750 dia concrete pipes as opposed to a massive trench fill to this depth. The top photo of this entry shows 2 of the 4 foundings for these pipes. On top of these pipes will sit large lintels which we will build the walls off. Our contractor has sourced some off-cuts of 750dia ventilation ducts (photo below) which will be perfect for casting the foundations.
In the meantime, the underpinning has continued this week and the rear wall is now fully underpinned. This has gone well, but there’s more to be done as we work our way up the slope of the house. The photo below shows the, recently poured, underpinning section with the formwork and bracing (granted not the most interesting picture, but I am a bit short of visuals this week!).