Day 24 - Starting the drainage

The first drainage run has been excavated, and bottom of the first inspection chamber put in place.


The drainage runs have been confined to the south side of the house, due to the extensive ground source heat pump loops on the north and east sides.  The public sewer runs just beyond the site boundary along the road, and has an invert depth of just under 6 metres.  We are connecting into the existing drainage used by the bungalow (because by the time we use the new drainage we will have demolished the existing drainage, so there will be no net increase).  This avoids us having to dig down about 6 metres to connect into the public sewer.

Day 23

The recycled concrete blocks arrived for the first part of the masonry foundations below ground level.  These 'Masterblock Enviroblock'  blocks boast a recycled content of a minimum of 80%, which was the highest percentage we could find.  It would be interesting to know if anyone knows of one with a higher content...


Ideally we wanted them located in the centre of the excavation, however the reach on the crane was not sufficient.  This was as far as they could get the blocks.

This was the other soft spot.  A perfectly circular hole!  Our best guess was a pole of some description.


Both the soft spots were dug out and filled with well compacted 20mm limestone.

...the bones!

We went over the whole footprint to check it was a firm base for our masonry, as we are not using concrete footings.  It was all rock hard apart from two very localised mystery soft spots.  These had to be dug out as they would not have provided a good bearing for our foundation walls.


This was the first - it was over two meters below finished ground level before we reached solid ground and it turned out to be a dogs grave (complete with a pile of bones!).

Day 22 - setting out the grid

We planned to set up timber bridges at a constant level, at each end of all grid lines.  These bridges were located using rough setting out marked with the tent pegs.  Accurate setting out of the grid was marked with nails in the top of each bridge, between which we could tie string to get a constant grid line.


We decided there were some areas we could not set out the grid today, as they needed further excavation.  The timber bridges would have been in the way here.   (And predictably it all took longer than expected so we also ran out of time!)

We ended up spraying our markers (tent pegs!) to make them more visible!

We planned to set out the main building grid today, so that we could set out the drainage ahead of it being dug on Tuesday.

Day 20

The excavated base is a mix of chalk and gravelly firm sand containing flint gravel with chalk lines.  It was not quite the continuous bed of chalk we were hoping for!  The main chalk area was in the back right corner of the photo.


In the front right corner the topsoil was much deeper than elsewhere (towards the back there is as little as 100mm in places), and was still present at the final excavated level.  We think that the chalk is about 100mm below this level, so we will need to dig down further and build the level back up.

Day 19 - Completing excavating the footprint

An amazing days work! Entire footprint excavated now! Thanks to James Knight Plant Hire & Construction, D S Plant, and A & S Topsoils.


We are now ready to start the drainage on Tuesday.

Almost there - excavating the last corner.


We needed the bottom of the excavation to be as level as possible, with not more than a 50mm variation across it.  It was regularly checked with the level, but it was virtually excavated by eye within 15mm.  Incredibly accurate, especially considering the soil variations.  Well done!

Another load of muck away leaving site.

DS Plant is back with the JCB!

Day 18

End of second day of excavating.

Day 17 - Starting the main excavations

Progress at the end of the first day of excavating.

Today we are starting excavations for the new house.  Our foundations are not traditional concrete strip foundations.  Instead, we are excavating the entire footprint of the new house.  We will then build up masonry walls directly off the chalk (that we are hoping to find when we excavate, like we did in the trial holes), which will act as our foundations and elevate our straw bale walls above ground level.  Within the foundation walls, we will start our limecrete slab from the same excavated ground level.

Day 15 - Clearing up the mess!

All done - what a good days work (and the new hedge is still in tact!).  Four loads of spoil taken off site - one to go...

The bigger diggers move in to backfill the trenches.

Day 14

Pressure had dropped to just under 3 bar today - which is fine.

All the sand is now backfilled, ready for filling in the trenches on Monday.  It looks like a hell of a mess out there, so it will be nice to start tidying it up!

A massive thank you to family and friends for all their help over the last couple of weeks.  We couldn't have got it done without them.  Thank you all!

Day 13 - Laying the pipe

We then pressure tested the pipe (we recommend a qualified plumber does this, who ideally is MCS registered).  The pressure testing kit was supplied by Nu-Heat with the pipe.  We  got 4 bar of pressure which was good and there were no leaks - phew!  We will now leave the pipe under pressure until we have finished backfilling all the trenches.  It is advisable when backfilling to check the pressure gauge every 1/2 trench, so if you pierce the pipe and lose pressure you know where the damage occurred.  The red marker marks the pressure at the start and the black pin will show the current pressure in the pipe.  We expect the pressure in the pipe to drop a little bit, particularly as the temperature is close to freezing most nights at the moment.  This is expected and does not mean we have a leak in the pipe.


Next task - backfilling with 100-150mm of sand over all the pipes.

The next task was to fill the pipe with water.  We tried first just wedging the hose in the end of the pipe - which quickly became unwedged (and narrowly avoided soaking the camera!).  So we applied one end of the pressure testing kit to the end instead and attached the hose with a jubilee clip.  It took between 15-20 mins to fill all 400 metres.

It slid on the pipe really easily.

Where the pipe crosses any services or comes within a metre of the proposed new house or itself, it needs to be insulated.  We used 13mm Armaflex Tuffcoat B (42mm diameter) which is designed for underground use.  It worked out about £12 a meter.

Laying the last run.  The pipe sat really well in the trenches after it had been laid.  We were concerned it would be trying to recoil and lift out. Even at the turns at the end of the runs the pipe was incredibly manageable.

Progress was rapid with the new method.  We laid 380 metres in about 1 hour (remarkably better than the 2 hours it took us to lay 20metres using the first method!).

Keep spinning!  The pipe was quite heavy to begin with - 3 guys could turn it but it was noticeably easier with 4.  It would have been much easier had the pipe been on a drum, which would have helped hold it together.

The pipe held together quite well.  Progress was much faster with our new method, but required much more man power.  Min 6 people required (we had 7) to turn and feed the pipe into the trenches without twisting it.

We decided to lay the pipe on its side on scaffold boards in a central position.  We would then spin the pipe and feed it into the trenches.  We started off with the ropes still on the pipe but quickly decided to take them off and see what happened!

It was time for a brainstorming session to think of a new way to get the pipe in the trenches!

It was really difficult to get enough tension on the loose ropes to hold the pipe together without denting the pipe.

We were making progress, albeit very slowly!  It took us about 2 hours to lay the pipe in about 1/2 a trench.

The pipe going in the ground!

We added two additional lengths of rope at the bottom to try and hold the pipe together better.  These had a loop at one end which the other end of the rope could pas through.  These could be loosened and moved as required.

We quickly ran into problems!  The pipe was difficult to keep on the scaffold boards.    Where it slipped off the boards the pipe would loosen on this part of the coil making it difficult to keep the pipe together and to wheel it forward.  It also became difficult to slip the rope round the pipe as its self-weight caused the pipe to spread at the bottom.

We needed to leave enough of a tail of pipe at one end to enable it to reach into the house (which starts where the pile of sand is in the photo).  We are locating the heat pump in the utility room.  Ideally we would have located it outside the house, in the shed.  However, the shed is going to be located where the bungalow is at the moment.  Logistically it was difficult to locate the heat pump here because we would have had to demolish the bungalow before we were ready to move out into the new house.  For this reason we opted for a Nibe heat pump, which are renowned for being very quite.  They are also MCS registered heat pumps, so qualify for the 'Renewable Heat Incentive' which is under consultation at the moment but expected to come into force next April.


Renewable Heat Incentive: This is a government initiative similar to the feed in tariffs for PV panels which came into force in April of this year.  More information can be found at http://www.rhincentive.co.uk/


Our trenches were very close to the propose new house, so we took our 400 metre length of pipe directly into the house.  However, if you wanted to locate the trenches further away, or if you required more than one 400metre loop (the length required was calculated by Nu-Heat as part of the ground source heat pump design) you could bring the pipes into a manhole.  Also supplied with the pipe loop are two 25 metre lengths of pipe which would be used to go from the manhole to the location of the heat pump.

The wheel of pipe set in motion on the scaffold boards with the rope holding it together.

Over the last week much thought has been given to how to lay the ground source heat pump pipe.  We thought about uncoiling it by the side of the road and trying to straighten it out before feeding it from the road up into the trenches.  However the access is now so bad from the road to the site (due to all the mounds of soil and sand) that we decided we would keep the pipe coiled and wheel it along the trenches on scaffold boards, uncoiling the pipe into the trench as we rolled it along.


We tied one piece of rope round the pipe in three locations (shortly reduced to two) that could slide round the pipe allowing us to uncoil it but still holding the pipe coiled together.  We then cut the ties on the pipe.


The pipe had caps on each end which we taped to the pipe to avoid anything getting in the pipe.

Day 12

...and the other end.

An overview of one end of the fully blinded trenches...

Day 11

All trenches blinded!  A welcome day off from the trenches tomorrow!  All ready to lay the ground source pipe on Saturday now.

An added challenge in barrowing the sand from the road - an uphill push!

More sand delivered ready for covering the pipes once they are laid on Saturday.  Because of the trenches we could no longer get access to the site, so the side of the road had to do!  We had to clear the overspill off the road straight away.

Day 10

So with all the diggers having left site, out come the shovels and spades!  A pick axe is also on its way tomorrow.  At least the sun is out!

And the mound of soil in this trench and the adjacent one is also not very helpful.

...this end doesn't look so good.  Yes, that trench is supposed to be straight!  We would like to point out, we are not digging these trenches ourselves!

All trenches dug.  This end looks alright.  But...

Day 9

Breaking the ends of the main trench runs out into the lateral gutter will be difficult as it looks like it is solid chalk.  Trenches should enter this gutter on the left hand side, at the same level as the gutter.  Where are they?!

Pace increased.  Almost completed.  However, looks like a lot of work to now join up the main trenches with the lateral gutters.  You can see in the picture the trench runs on the left hand side finish much higher than the lateral gutter and need the ends breaking out.

Day 8 - Still digging

Progress was frustratingly slow today.  Only 1.75 trenches dug compared to 3 on Friday.  Looks like the trenches won't be completed tomorrow.

Day 6 - blinding the trenches

All done!  Much quicker than expected, only took about 3 hours with four of us.  Amazing!

One completed sand blinded trench!