Groundwork: Part 4 - Oversite and drainage

After a few days the foundation walls were strong enough to withstand the weight of a mini-digger which Kevin (Nick-the-blockie's brother) manoeuvred into position to start work on levelling and compacting the soil within the new house. (Click pics to expand)





The first of many stone deliveries that would arrive over the next few days.





All the loose soil was removed from the oversite and the underfloor void was then gradually built up using the freshly-delivered stone.

Alan and I smashed up the old patio tiles and garden paths and used them as hardcore to help backfill the trenches all the way around the house. 





A wacker plate was used to compact the stones in layers. Alan found it such good fun to use that the groundworkers had trouble prising it off him.







75 tonnes of stone and much wacking later, we'd finally reached the right level.









You don't get much drainage gear for £800. Even with our 80% 'trade' discount.





The mini-digger was small enough to fit round the side of the existing house which made digging the trench for the water supply a lot easier. We laid the pipe from the borehole through to the utility room of the new house where we will fit all the water filtering equipment.

Please Note: The tree in the background has formed a suspicious shape of its own choosing - nothing to do with us...

Trying to connect the new sewer pipes to the existing septic tank caused much head-scratching onsite. Remember those carefully-constructed drainage access points (see previous post) in the foundation wall? Well (cue Laurel & Hardy music) it turned out that these weren't actually built high enough. So in order to get the required fall, we needed to knock out several blocks from the wall and place the pipes directly on top of the lintels that were supposed to be above them. Grrr again.       





Pipes and chambers were laid on a bed of pea gravel and then adjusted to get the 1:40 fall required by the building regulations. 





Along with the sewer pipes, the stormwater pipes that will eventually connect to our roof guttering were also set out ready for inspection by Building Control. 









Alan and I covered the stone with a layer of sand blinding which is used to stop any sharp stones from puncturing the plastic damp-proof membrane that goes on top.  





As we live in a 'full radon' area, Alan constructed a radon sump to comply with the regulations. The sump (or pile-of-bricks-with-a-paving-slab-on-top) is connected to a pipe that runs from the centre of the house to an exit in the outside wall. If there are ever any dangerous radon gases building up under our floor, the sump can provide an easy way to get them extracted safely into the open air. 

After the sand was given a thorough going-over with the wacker, we were ready to lay down the damp-proof membrane and finally pour the concrete floor slab. Or so we thought...

Groundwork: Part 3 - Blockwork foundations

A few days after the concrete footings had been poured, we were able to begin construction of the blockwork foundations. After carefully setting up lines and levels, the block laying was ready to begin.





Alan carried over and laid out the very heavy (28kg each) trench blocks in readiness for our blockie Nick. Despite ignoring my sage advice about not overdoing it, he then proceeded to complain about his bad back for three weeks afterwards (tut).
 

With Nick's son and regular work partner away on honeymoon, Alan pitched in helping to mix the mortar and acting as general labourer.









I wanted to try my hand at some blockwork and after a quick lesson from Nick, I gave it a try. As you can see in this picture, after laying one block I'm now a real pro.













Openings in the wall were created for drainage pipes and the water supply pipe from our borehole.







The initial intention was to only build up 4 courses of trench blocks. We decided to add a fifth course in order to raise the floor level. This helped compensate for digging down much deeper than planned when the site was originally cleared.





It almost seems a shame to spend so much effort on a neat blockwork wall that just gets buried under the house & never seen again.






With the blockwork completed, we were ready to begin work on the ground floor construction.

Groundwork: Part 2 - Trenches & footings

With the site cleared & levelled, we were able to begin setting out exactly where the new house would be built.







After the perimeter of the house had been set out and marked on the ground, the trench digging began.





Disposal of the muck would normally be very expensive as it would have to be transported to a licensed pit, however we managed to strike a deal with the local farmer (more on that later). Our excavated soil was dropped in the dumper truck which was then unloaded into a nearby field. Considering the amount we ended up removing, this arrangement saved us a small fortune.  







It is quite hard to budget accurately for groundworks because you never quite know what the soil conditions will be like until you start digging. The original plan was to dig the trenches 900mm deep, however the groundworkers felt that the soil at that depth was still too soft and ended up going to 1400mm. A bigger hole in the ground meant a bigger hole in our pockets as more concrete would have to be swallowed up.





After the Building Control and warranty inspectors had visited (both seemed puzzled why the groundworkers had dug as deep as they had - grrrr), wooden boards were put in place to help prevent the trench collapsing overnight as heavy rain had been forecast.





Steel pegs were set out using a laser level to mark the height of the concrete fill. Building regulations only required 225mm concrete but thanks to our deeper trenches we were now looking at more than three times that depth.







The next day after clearing any collapsed soil from the bottom of the trenches, we were ready to start pouring the concrete. A brand new lorry with a fancy remote-controlled conveyor resembled something out of Thunderbirds but was perfect for reaching the far corners of the site.

 


 







More rain overnight had caused the trench walls to collapse in places but luckily the concrete had already set well before the rain arrived.