Rubber-up

Apparently another month has somehow happened in the seemingly few days since I last posted on here.  I've been doing a variety of small jobs, all aiming towards getting the outside sealed and the whole thing watertight.  The roof is now watertight, thanks to EPDM membrane expertly installed by the guys from Ken Whalley Roofing in Weymouth (the nearest installers).  EPDM is a synthetic rubber, it's incredible strong and durable including in exposed positions - it doesn't degrade in sunlight, flexible (allowing for movement of the building without damage) and when installed correctly is totally watertight.  For all of these reasons it's often recommended for use as the waterproofing layer of green-roofs.  As modern roofing materials go its environmental impact is relatively good too: it's calculated to have a global warming potential of just under 7 kg of carbon dioxide per square foot.  This still sounds quite a lot to me, but it compares with 11kg CO2/sq.ft. for PVC, and just under 12kg CO2/sq.ft. for modified bitumen (the common roofing felt seen on lots of garages and leaky extensions) and a whopping great 20kg CO2/sq/ft. for built up roofs (bitumen in layers with other materials). [source of data: http://www.epdmroofs.org/3.2_Supplement_LCA.pdf].  The manufacturers claim that no toxic materials are released during it's production or installation but I haven't found the hard facts to back that up yet.  I see it as the least-bad option, definitely lower-impact than most alternatives for the job.

The edge trims for the EPDM system (the visible finishes around the edge of the roof) are smart and crisp but very much standard.  It's metal with some kind of plastic coating.  This covers the join between the rubber membrane and the timber fascia board.  It's bugging me a bit at the moment, this trim and the large white fascia boards we've ended up with.  The original plan was that the fascias would be the same depth as those on the existing bungalow, but for various practical reasons they've ended up slightly larger.  I don't know what the alternative would be but I suspect with a bit more time we could have found something a bit softer to look at, and more in keeping the rest of the build in terms of natural materials.

There's a stark mismatch (in my mind anyway) between the fascia and trim at the top of the extension, and the lovely natural oak render-stop that now lines the bottom edge of the straw walls.  Hopefully this will become something I don't even notice but right now it's niggling at me!

sealing the cavity around new corridor opening into extension

This represents a major lapse in sustainable materials use.  It's polyurethane foam insulation (Kingspan/Cellotex etc). High embodied energy and quite polluting in its production.  But it's hard to find a more sustainable alternative for this kind of application (any ideas please tell me).  The roof lights extend above the rest of the roof and so above the insulation layer in a smartply box; this box would be a huge thermal bridge, rendering the triple glazing pointless.  So the PU insulation provides a high level of insulation around that box without adding too much width.

Awkward triangle gap above wall plate on outside wall.  Using baling needles I restrung the bales with strings angled to match the roof pitch, then strimmed the excess straw off until the strings were exposed and the bales triangularish. Then bashed them into place with the Persuader.  The even more awkward spaces at each end of the gap are stuffed with lots of Thermafleece sheeps-wool insulation

Trimming straw on the gable in the Tent Of Doom

Tim fitting cavity trays.  These bridge the cavity and catch any water that finds its way into the wall above the extension roof, forcing it out onto some flashing and then onto the roof - not down the internal wall of the extension.  It's a bugger of a job and I'm very glad I didn't do it! They're plastic, but 100% recycled plastic and made in nearby Yeovil.

Supermarket fascias at the back (they look smaller now the trims are on)

The gazebo finally died after a particularly stormy night.  It's been held together mostly by gaffa tape and bailer twine for most of its working life.

More rain dripping off the new roof and glistening in the sunshime

At end of first day of EPDM work.  The membrane is wrapped over a timber just below the tiled roof, forming a gutter that will channel water from the tiles roof away from the green-roof so that it can be collected in the rainwater harvesting tank.

Bendy panorama of half a rubbered roof

Cavity filling pipes. Filling the cavity in the bungalow so that there's a continuous layer of insulation, and not a big unhelpfully ventilated space between the indoors and the new bale-wrap insulation.

It's filled with chopped up glass-fibre, made from recycled glass

The walls hummed and made a range of interesting sounds as the fibre was pumped in.

Rubber roof

Last bit of brickwork, to line the entrance.  Screws behind it to provide improved key for the render to stop it falling off the timber.

studwork to form wall between the great outdoors and the bungalow, under the back porch and conservatory roof.

Nice bit of flashing by the gulley where the tiled-roof water is funnelled.  Went for lead-flashing this time.  Flashing choice for green-builds is tricky.  Lead is quite toxic, throughout mining and production, and installation, and use.... But - it is also incredibly long lasting and recyclable.  It can be taken off very old roofs and reused immediately.

Finished EPDM, trims and fascia boards.

Oak render-stop.  The lime render will come down to this, flush with the outside edge of it, then stop.

I spent a morning in Darren's workshop planing the front of the render-stops and routing a drip groove in the bottom (so that water drips off rather than being drawn underneath onto the wall).  He called me a cowboy when I said I was just going to screw or nail diagonally through the top of the render stop to fix it.  Suitably shamed I followed his advice and drilled countersunk screw-holes in the front and cut same-sized plugs to fill the hole once the screws were in.  Bit of a pain but very satisfying when done.

Highly manufactured trim at top, lovely timber detail at bottom.  Plus recycled wall for 1st layer of path build up.

Top to bottom: straw, Douglas fir, oak (with plugged screw-hole), lime mortar and slate damp-proof course, fired clay brick.

Temporary rainwater downpipes and supports from skip.  Not sure if it's arms or legs.

Reed mat on the stud-frame between conservatory and bungalow.  This will be plastered onto.

Preparing for render.  Laths and reed mat provide something for the render to cling to where there's no straw (which makes a brilliant surface for render to stick to).

Reed mat bridging gaps and covering the timber wall plate, again so that the render has something to hold to.

Beyond burning

The extension and conservatory are now well on the way to having a proper roof, thanks to Tim and Mike who've been dealing with various complications from multiple angles of roof and unusual details.  It's been great to watch the roof growing across the site.  Mike and Tim came on the volunteer weeks for the strawbale building which seems very serendipitous for me as I didn't know who was going to be doing the roof and they turned out to be excellent carpenters.  It also meant they were able to talk to Kuba (building designer www.jakubwihan.com) about the structure and resolve at least some of the details while he was on site.  They've been very helpful too, giving me advice on my first experience of timber framing for the conservatory/rear-porch supporting timber-frame and various other bits and pieces.

I really enjoyed building the timber frame (pictures below), with occasional assistance from volunteers Robert and Steve.  My previous experience of working with wood has essentially involved mostly chopping it up and burning it to fire kilns, or walloping bits of it together with nails to form basic kiln sheds.  It's very satisfying to work a bit more sensitively with it, cutting mortice and tenon joints and half-lap joints and fixing it together with wooden dowel and glue rather than screws or nails.  The joints are - unsurprisingly - not the neatest and don't bear up to too much close scrutiny but they're pretty much in the right place.  The whole structure is more or less square and true, is where it's meant to be and is now holding up the new roof across the back of the bungalow.  I find this last bit in particular both very pleasing and very unnerving.

The roof will hopefully start to get it's waterproof EPDM rubber waterproof coating next week, the windows and doors have all been measured up and are now being manufactured, so things are moving along.  There's ridiculous amount still to do, not least trying to get some render on the straw before it's too late (ie: before it gets frosty out there).  As throughout the build, the trick with not freaking out is to keep dealing with one thing at a time.  If I look at everything that needs doing I'm prone to larger than normal amounts of gibbering.  If I focus on the task in hand (whichever task it is) then I can get it done and mostly enjoy it (with the exception of priming/undercoating both sides of 40 metres of fascia board - today's task and a particularly dull one).

Building doorsteps up to correct height so that when the frame is fitted the top of the frame is level with finished floor level, producing level mobility thresholds. Timbers of the same size as the one above also fitted to the sides of the door and window openings, to form the box that the doors/windows will be fitted into.

Front doorstep doctored for same reasons as above. Bottom hacked off door so it can remain in place until last possible moment.  We're having different types of door in different places, all with different thicknesses of frame, making calculating what height to set the doorstep a right old headache!

Stage one of conservatory structure - eaves beam on (very) temporary support.

Extension roof structure taking shape.  It's a shame none of this will be visible, it's beautiful!

The most complicated carpentry I've undertaken.  Notching top of glulam timber post to support eaves beam and cross-timbers.

The post in place, with douglas fir cross-timbers and glulam base-plate added.  It's all pegged and glued, no screws.

Self-supporting now.

My first foray into timber-framing, nearly complete.

Breather membrane on extension roof.

50mm battens on top of membrane to provide ventilation above it (to remove any condensation).

Raining again.

Mike finds out whether my timber frame is at the right height and can support the rafters.

Timbers and membrane across conservatory, brickwork built up to frame.  Very very satisfying.

Last details of the timber-framing, notches cut to receive tongues of a diagonal timber.  Working this out took a disproportionately long time.  There was a lot of standing up a ladder with a tape measure, a square and a bewildered expression.

Ta-da! It fitted - phew!

Straw to the left: strimmed, ready for render.  Straw to the right: not yet strimmed, straggly, not ready for render.

Trimmed end.

Trimmed corner.

Soffit overhangs taking shape.  These will keep the worst of the direct rain off the walls.

Boarding the roof with Smartply, highly sustainable OSB/Oriented Strand Board: formaldehyde free (unlike most OSB) and made from forestry trimmings/waste.

Fitting lintels ready to cut new opening for corridor into extension.  Had a long drawn-out and very boring saga with these, trying to find a way to get them above ceiling height so we could have continuous ceiling level through the opening, whilst still supporting a critical structural beam of the exiting roof.  Turned out that all the lintels capable of supporting that beam and its load were too big (apart from one that was specified but appears not to actually exist), so now there'll be a slight step in the ceiling. 

Roof windows fitted, nearly all boarded.  The roof is huge when viewed from above - partly because it comes up over the existing roof by quite a lot.

Outer brick skin removed, no collapse yet, good.

Brick Man (after using the dust-monster disc cutter to cut the opening above, wearing goggles and mask).

Up on the rooooof....

Dust.  This is just the dust that spilled outside when cutting through remaining bricks from the inside.  On the inside, with a tarpaulin hung to contain the worst of the dust I was in my own private dust cloud.

PPE Man (PPE: Personal Protective Equipment).  Suitable attire for cutting holes in walls in a personal dust cloud, when mistrustful of bricks/lintels and not wishing them to fall on my head.

New opening!  Felt momentous.  Now boarded over to maintain security.

Roof and internal gutter now fully boarded and ready to be covered with EPDM rubber waterproof membrane (the least toxic/polluting and lowest embodied energy option for sealing the roof beneath the green-roof build up.  Also extremely durable and reliable.