' the Woodlouse: June 2012


Thursday, 28 June 2012

The bales! The bales are coming!

Before the groundworks began I hadn't really taken in the complexity of the new drainage, rainwater harvesting and soakaways.  In fact that's been far more complicated and taken far more time than digging the foundations.  Access around the bungalow is very limited and once the groundworkers have put a drain in somewhere they can't drive back over it with the digger for risk of crushing it.  I've been impressed repeatedly by the skill of the groundworkers and how well they've planned the work so they can get to it all and then escape from the site.  I briefly considered attempting all the digging myself but I'm so glad I didn't.  It would have been a right mess.

There's one set of drains to channel rainwater to the tank from the tiled (relatively clean) parts of the roof.  Another set of drains take rainwater from the green roof to a soakaway, avoiding the harvester tank.  Then there's the soakaway and the harvester tank themselves.  Finally there's the new foul drains (sewers) from the toilet in the extension and new drain from the existing bathroom, now linked up to the old sewer.  A lot of new pipework!  But it should all help to make the bungalow fit for the next 40 years and beyond.

All the foundations are now dug, hooray!  I'm so happy to have the extension foundations dug at last (and to have some hardcore down under it, the lagoon of mud is no more).  The new-build strawbale extension feels in some ways like the main part of the project, though in reality it's probably the most straightforward part (ugrading the existing bungalow is much more complicated).  Straightforward but blooming hard work, below ground at least.  I've spent most of this week shovelling gravel and going over layers of it repeatedly with a compacter plate (Wacker machine), following the same design of cement-free foundations as for the wrap and the conservatory (see last blog post) only on a much bigger scale.

The structural engineer and building inspector have insisted on 1 metre deep foundations because of the clay it's built into, and the wide bale walls mean wide foundations (70cm wide).  When it was dug out it was basically a moat, rendering the extension area inaccessible.  So far 17 tonnes of stone have gone into the those foundations.  I had help from one of my sisters and my brother-in-law who wonderfully re-arranged some of their week so they could help me.  After seeing the scale of it Caroline came back for a bit the next day too.  I think with their help we got about 8 tonnes in (it comes in 1 tonne bags), leaving 9 tonnes which I seem to have shovelled in on my own.  I'm stiff and I ache an awful lot but I seem to have got away with it.

I've mostly managed not to look at the whole amount to do with the gravel and just to plug away at it.  A certain amount of delirious hysteria has definitely crept in though.  I hope my future neighbours aren't bothered by me talking and laughing to myself as I stumble in and out of the moat with a shovel, a rake or the magic beepy stick (laser site level).

Another - hopefully final - 10 tonnes of gravel are now onsite (at least, they should have arrived this evening, I haven't been up to check) hopefully to go straight in the foundations first thing tomorrow, this time with help from the builders.  I've caved in and called them back to help because the bales arrive tomorrow too.  The only place the bales can go is in the level area that will be the extension, and they can't go there until the gravel isn't in the way.  The gravel can't be stored anywhere else either: the only other possible space needs to be clear for a new water pipe to be dug through it on Saturday.

I'm not ready for the bales, they're going to be in the way, but understandably the farmer who produces the dense, regularly-sized construction bales needs his barn-space back.  The phone call saying he was sending them on Friday, essentially whether I'm ready or not, tipped the balance of calmness well towards the manic.  I feel like a green-build Quasimodo, hunchbacked from all that gravel, stumbling around exclaiming "The bales! The bales!".

During the week I read this blog about strawbale selfbuild by Andrew Morrison (www.strawbale.com/staying-sane-during-your-build/).  I seems like sound advice and I was pleased to find I was already following most of it.  Number 1 is "expect the stress".  Wise words.

Hole for rainwater soakaway.  Water from the tiled roof will collect in the rainwater harvesting tank, but still needs somewhere to overflow if there's a storm and the tank is already full.  More lovely clay stored up now from this hole.

The soakaway crates.  Simple way create a void that can fill with excess water before it soaks away, without recourse to huge amounts of reinforced concrete.  It's wrapped in geotextile to prevent ingress of roots and soil.  Although it looks like just glorified milk crates, apparently you can drive 20 tonnes over it once it's buried.

Lowering it into the ground with the digger.  I had a brief funny moment here, when excitement at getting it done mixed with odd feelings about the grave/coffin-like nature of the whole thing.

Anna watching, with support from apple tree

100mm of pea gravel on all sides.  Cleared area is where inlet pipe now sits.  The inlet flows from a leaf collector after the harvester tank (which sort of spits out any leaves that get in to the filter at the top of it).  The rainwater from the green roof will join the drain at the leaf collector and flow straight to the soakaway (chance of fine soil particles in it - would clog harvester tank over time)

Covered back over with the turf so carefully removed by the groundworks guys.  very neat job.

A rare dry moment in the mud.  Running through this area now are two sets of drains (one for the harvester tank, one straight to soakaway) and the tank itself.

Fully functioning plumbing.  The loo is belatedly joined by the sink in their new location (though probably not the loo and sink we'll ultimately use).  I find (successful) plumbing very satisfying.

Couple of small test holes to judge level to reduce-dig to for the extension.  Filled with rainwater of course.

Foamglas (cellular, airated insulating block made from mostly recycled glass).  Very high comressive strength too.  Will form the inner wall of the foundation plinth that the bales will sit on, making the foundations themselves insulating to cut down on heat loss through the floor and foundations.

Ready for setting out string-lines for brickwork.  Or for vampire attack.

Natural Hydraulic Lime (NHL) for building the foundation plinth walls with (mixed 1:3 with sand to make mortar)

Bricks and sand too.  Might actually get to do some building soon!

Making the most of the quality clay we finally found in the tank and soakaway pits to make some rough clay plaster tests.  Aim is to gauge roughly what proportion of sand and clay will produce strong plaster without too much cracking.  In reality the plaster will be made up with finely chopped straw too.

Reduce dig for the extension, removing the mush and finding harder ground

Replacing mush with hardcore

Blue line marks the outside of the foundation trench

1metre deep, 700mm wide.  Pink area in left side of trench = where the manhole for the old foul drain was dug out and back-filled

New drain for the toilet in the extension and the sink in Anna's studio.  Connects with the new drain from the bungalow in the black inspection pit.

Grey-line to the right is another new rainwater drain, which will collect run-off from the green roof.

Lovely straight-sided trenches messed up by the concrete strip foundations for the old garage sticking a few inches into them - so had to be taken out, hence big holes on left.

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So that's where the rainwater's been going: small soakaway made from rubble at the base of the downpipe.  Considering these little soakaways appear to have worked fine, our ridiculously oversized one certainly ought to do the job.

This was once the front lawn.  Nearer pile of more-yellow earth is another store of lovely clay for plaster.  The rest is the rubbish from most of the extension footings.  Towards the back of the bungalow the ground is all mixed up rubbish, made-up ground from when they built the bungalows.  Towards the front the clay is nearer the surface as it follows the original sloping ground level.

Final foundation trench finished! Clay just below the surface here.  The existing bungalow foundation were clearly just dug into the top of the clay only.  They step down towards the back as the clay goes down the hill.

Supports for rain-cover

Covered to try and prevent them filling with rain before I can fill them with compacted gravel

Earth-pile neatened up a bit and sealed while it awaits removal.
Open to the morning sun the next day

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I used to do paintings that looked a bit like this.  At least, this is how they looked in my mind.

The dark line is the original ground level from before the bungalows were built, sloping off downhill to the left.

Giant trench lined with geotextile and ready for gravel to go in, as before compacted in layers of 100 to 150mm

Much time this week spent with just me, a shovel, a wheelbarrow, and a whole heap o' gravel.  I had help for about 8 tonnes of it, leaving 9 that I apparently shovelled in and compacted alone.
The dog inspects the foundations

The far side of this trench started to collapse from the weight of the forklift pushing down on it after Mark the builder fork-lifted the bags of stone into the middle for me, so I had to get it filled quickly before it could cave in.

Underneath the covers.  It takes about half an hour at each end of the day to uncover and re-cover the trenches for the extension; trying to keep them dry and safe from rain-induced collapse until they are full

17 tonnes of "40mm clean" gravel, and still the darned trenches aren't full.  Another 10 coming tomorrow.  I've given in and asked the builders for help so we can get it in asap.  Apart from anything else we need it out the way so there's room for bales when they arrive!

Monday, 18 June 2012

Cement-free foundations

Just about there with the blog catchup: from here on I'll try and update more regularly.  Today's thrilling instalment: cement-free foundations.  I think I've talked before about reasons to avoid using cement-concrete (I'll check and rectify that if I haven't), but in brief: cement has a very high embodied energy and very large amounts of C02 and other pollutant chemicals are released in its production.  We're using compacted gravel and limecrete - lime requires less energy to produce than cement, less CO2 is released in its production, and it then re-absorbs some of that CO2 as it cures and carbonates.

Foundation construction details with the photos below.  But first, this:

Clearing the mud left at the bottom of the foundation trenches after days and days of torrential rain.  I'll try and make sure the next foundations are filled asap after being dug...  Note 'tide mark' from water level, about a foot up.

Geotextile lining the trench.  This will prevent the clay-soil from permeating through the gravel infill.  Clay soil tends to moves as it expands/shrinks when it gets wetter/drier (this is why our foundations had to be so deep).

Foundations for the strawbale wrap sit on top of the existing concrete foundations of the bungalow

Eventually, this will be the kitchen area.  That pile of rubble came from the trench through the utility room where I was re-routing the foul drain

More emergency guttering.  I didn't have enough downpipe so used the tubular plastic bag the geotextile came in.  Water flows down the bag and into the pipe (incidentally, this is how silenced toilet cistern valves work, sort of)

Whacking with a wacker.  Compacting the gravel in roughly 150mm layers.  The gravel is known as "40mm clean" meaning there's no dust or fine particles, which could produce similar unwanted result as clay particles getting into the foundations.  It also allows the foundations to be draining.

Chunky gravel is a pain to shovel.  Much easier to dump it out on a hard surface and shovel from there (even better to use a mini-digger to shovel it off the ground into wheel barrows, like we did)

Finished gravel level.

Excess muck being removed from site.  I'd hoped to re-use it all on site but there's too much coming out of the deep excavations.  This stuff is a horrible mix of old building rubble, soil, clay and general muck in any case.  We have a lovely big pile of purer clay to use for clay plaster

Cores from core-drilling the wall.  Left hole is for the drain from the bathroom and utility room, right hole is for the service pipe from rainwater harvesting tank.

After about a week with no loo, I reconnected it in roughly its new position, into the new drain.  Not worried about neat plumbing at this stage... Still hoping to replace the water pipe that enters the house anyway.  Current one is corroded and unlikely to last as long as we'd want.  We should find the main underground pipe once we dig out the extension footings.

Aerial view of new drain from bathroom.  Coffee cups showing need for the sink to be reconnected.

A final layer of geotextile to separate the limecrete from the gravel

Short lengths of rebar (reinforcing bar) embedded into the bungalow wall with resin, to tie the limecrete to existing structure.  The was a dearth of the correct size of rebar in town.  Getting it sorted involved a trip multiple builders merchants, returning to one a second time, armed with bolt-croppers I'd just had to go and buy from another supplier, in order to cut the rods to a size that would fit in my car.  Drain and service pipe entering bungalow below floor level.  All of this was inspected and approved by the building inspector just before limecrete arrived.

Ready for the off

Ready-mix limecrete.  Not as local as I'd like, but the nearest available (possibly the only supplier of premix limecrete outside of Norfolk).  It saved me days of mixing small batches.

Mark showing me how it's done

The face-spattering device

Checking limecrete level with the magic beepy stick (laser site-level, wonderful bit of kit I will never own).

Me hunching over the beepy stick, my sister Caroline hunching over a barrow of limecrete.

Wheelbarrow sloppy races

Conservatory foundations.  Some last minute shuttering was needed here as the ground was a bit lower than intended.

In order to carbonate properly and harden fully, lime needs air and mositure - not loads of rain washing it out, and not sun drying it out.  The timbers are to hold the rain/possibly-sun protection off so that air can get in

All wrapped up.

Fully be-skirted bungalow.  Re-using the plastic that functioned as temporary roof covering earlier in the build.