Tuesday, 5 July 2016

Building the extension slab

The rain held off for 24 hours so we cracked on with shuttering and filling the trench with a strong concrete mix, and reinforcing bar because of the clay underneath. Our trench was around 18-inches deeper than the bottom of the hardcore, and a further 36-inches below finished floor level.

We had to lay some old smashed concrete on the slab area just to walk on it without collecting clay-mud on our boots.


Because the house itself has no foundations, and the bottom of the stonework lays at the exact level we are building UP to with the concrete, we were in great danger of causing a collapse of the house. So an important task we did in carefully managed stages (not many pics to illustrate it, sorry) was to build a large concrete buttress below the corner of the house.

We did this by creating a form-work out of concrete blocks, and carefully digging in to the clay below the corner, We hammered in several rebar sections and then filled the area with a strong concrete mix 2ft deep and 4ft long. 



Whilst that set, and before we did any more work in scooping out the clay near the house, we set about moving back in to the slab area tonne after tonne of hardcore. It took 2 full days with 4 people to hand-shift bricks, concrete, tiles, slabs and stones, smashed down to half-brick and smaller sizes to fill the slab area and make a stable base on top of the clay. Worst job we've ever had to do.


In fact, we ran out of 'clean' hardcore so we had to start sifting through the earth which we'd dug out of that hole to get large stones and bricks to throw back in. We ended up with around 10 tonnes of earth left over, which a kindly local farmer took away to fill some holes!


The amount of materials used in the extension has boggled my mind. My rough calculations are that, to get to finished floor level, we've hand-shifted in barrows 23 tonnes of 'stuff'. I'm not kidding when I say that I now have a knackered back and a new appreciation for labourers. 


By day 4 of having the Builder on site, we'd got the first blocks up towards finished floor level.

Here's a day's effort of filling that level with hardcore. The top of those blue bricks is finished floor level to give some appreciation of the task in hand.


Our trusty barrows - three at a time in operation during the day.


On top of the hardcore went down a layer of scalpings, which were whacker-plated to flat. You can see that below. On top of THAT went a layer of sand to smooth off any sharp corners, and then a layer of Kingspan insulation.


And eventually, after what was only 8 days but which seemed like an eternity of barrowing, the Builder got the concrete laid and level, and it started to look like a floor. Hoo-flippin-rah.

Foundation trench for the extension

Oh good, it's forecast to rain for the next week, just in time for the heavy clay foundation trench to fill up like a swimming pool. How we laughed.

When we finished laughing we strung up an enormous tarpaulin to try to keep as much of the rain off the trench as possible. You see, once the rock-hard clay/stone mix of ground got even the slightest bit wet, it turned from ground which you'd have serious trouble getting a spade in to, to ground which you'd have serious trouble getting your shoes out of.


That was a horrific couple of days of soul-destroying shoveling to get the trench to final depth (4ft-plus below finished floor level) and the entire area of the slab down to a flat and stable 3ft below finished floor.

Clay, you see, shifts and moves and grows and shimmies as it absorbs water, so the regs say you have to go deep, and provide a solid, heavy, reinforced base which won't cause your extension to crack. To hell with the fact that your house's foundations are (literally) above the finished floor level you're aiming for, and that it's just plonked down on the clay.., that's old building with stone and lime versus modern thinking and materials.

And the rain, as if to illustrate the fact that the clay was absorbent, kept on coming. Our tarp served to redirect most (not all) of it in to a bathtub we rigged up, where we pumped some away, and watched as more filled our trench repeatedly. It was frustrating, shall we say.


But in the end we got there, and you can see the bottom of the trench, where we threw in some spare Glapor to give us a walking surface, versus the finished floor level (see the gravel line on the house wall).

It took 3 days of manual digging and fettling to get the levels right. 

Tuesday, 10 May 2016

Reinstating a brick arch doorway pt2

Last night I decided to crack on with the brick arch so we can block up the doorway properly and get a little security back in to the house.

I started off by tracing the curve of the existing upper arch bricks (which have loosened a little more), and cutting a 110mm smaller radius in to two sheets of 18mm ply.

I nailed those two sheets to a block so ended up with a curve that you can balance a brick on.

It was then a case of holding it in place and mounting it to two uprights to keep it in place.


I chose 9 clean but old (reclaimed from a now-removed chimney stack) bricks and placed them in to the former to check for size and fit. It also tested the former for bearing the weight of the bricks whilst they dried.


I gave the existing arch, and the new bricks a good soak in water to stop them drying out my NHL5 lime mix, and then set about the task of 'mucking them in' using that lime.

It was a particular pain of a job, and the last brick had to be persuaded in to place with a rubber mallet.


The new arch was allowed to dry for 15 hours so the lime had a chance to harden (but not yet completely go off). Then I slowly relaxed the support from the wooden former to see if anything was going to slip.

It held fast, and is now slowly drying.

Sunday, 8 May 2016

Reinstating a brick arch doorway

Further to the last post, I had a brief conversation with a blacksmith (who happens to be a dab hand at period property renovation) and who assured me of the structural virtues of brick arches. And that, if I could support the arch whilst doing it, adding proper supports both sides would give more than enough structure to safely resurrect the arch without need for an iron bar.


So I sat with a cup of tea and planned how to attack the job, and in what order things had to be done to stop the thing collapsing.

The arch bricks are deep, and supported by two separate oak lintels. I was able to cut away the larger of the two lintels and remove the fill above it to expose what I was working with properly. The large protruding stone on the left is huge, and solidly embedded in the wall, so it gives a good platform for building another layer of stone on top and the arch off that.

On the right, the oak has been cut and left in place (it took a hell of an effort with a chainsaw!) and will form the basis for a platform on the right hand side.


Once cleaned up of all the old lime and bits of fill, the protruding stone shows a really nice flat face for mounting another stone on top of, and by using an oak wedge, and bits of stone fill, I was able to balance a perfectly shaped (and interesting) stone on top of this, lock it in to place and then use NHL5 mix to secure it in place.


I had to cut the second oak lintel in order to get the new stone in to place. It's enough of a cantilever to hold the remaining fill and brick arch up until the NHL cures (dry in 2 days, cured in 7-10).


Once it's cured, I'll build a wooden former and add another layer of bricks to form a lower arch - the aim being to match the height of the outer arch - which you can see in the above photo is about a course of bricks lower than the inner arch.

The new head height of the doorway, with a raised floor to minimise the issues with our lack of foundations, will be around 6ft at the middle of the arch. That's a couple of inches higher than some of our internal doors!

Saturday, 7 May 2016

Raising a doorway

In tandem with planning a step up somewhere in the extension, I began looking at ways to increase the head-height of the doorway from the main house, and as such allow us to raise the floor level even further without compromising too much.

You can see the faint outline of an arch above the doorway, so today I set about investigating if that was structurally intact and whether it would help our problems.


The external arch is sound and strong, and has been supported by a large protruding stone on the right of the doorway. It was easy to remove the modern-ish door and frame, and peel this back to the original arch.


However, I suspect that when the 1880 extension was built, they did a fair amount of buggering about with this doorway and pulled out some of the internal side structure. They put in two oak lintels, about 3 inches deep and 6 inches wide, and bricked up the internal arch.

The lintels aren't sat on any kind of structure on the left of the picture below (except for a bit of lime holding them in place), so I had to think of the best solution to create a taller door and keep the structure.


I've decided to have an iron bar fabricated to support the internal arch - similar to the ones used to support curved fireplaces. I can cut this in to the stone on both sides and it will prevent the weak arch collapsing. Above the arch sits another oak lintel (shown in above photo) which is taking most of the weight of the 2nd storey walls.

More on this when the builder has confirmed my plan looks OK.

Digging extension foundations

We hired a 1.5t minidigger and a skip-lifter for the weekend in order to dig out the foundations for the new extension.

We've planned to have a continuous floor level from the doorway you can see at the top right of the below photo, to future-proof the new bathroom and study for less-able people. 

We hit thick yellow clay mixed with rocks after 6 inches of gravel (the previous extension's foundations!) and it took some serious skill on the digger (not by me, I should add) to get the area clear and vaguely level.


Once we were down 18in from finished floor level, we set about planning the foundation trench, which will be a further 18in deep, 2ft wide, and be filled with reinforced concrete.

Getting the digger to work at any sort of decent angle to the trench in an area 4m x 7m was hard work, and the trench was slow-going.

In the end we decided that a slope-sided trench would have to do, and gives us the option to shutter and backfill the sides if needs be later.


By the end of day 3 it was as complete as we could do with a digger. The rest would have to be done by hand. And as you can see we're considerably lower than previous ground level.


In fact, that ground level thing through up a bit of a nasty surprise. We'd often wondered what the large concrete moulding on the end of the house is. I finally twigged its importance today! 

When the house was built, it was built in to a hill. Original ground level was at the height of the line 18 inches up the concrete moulding (where it goes smooth). 

At some point in the past, that 18in of clay has been removed to increase drainage and allow for a walkway around the side of the house.

BUT, the house has no foundations, and only a couple of courses of large stones which were originally in the ground! What you can see in the picture below is it... there is no more stone beneath those walls - only clay and small rocks.

Suffice to say that, once I discovered that, all work on the digging stopped.


You can see in the photo below, towards the barrow, a dark line on the wall. That's the sub-foundation clay on show. It was quickly covered back up to keep it from drying out, and what you can't really see in these photos is that the digging-out from that point comes outwards at 45-degrees, so structurally we're still dissipating the weight of the house OK.


However, this does put any plan of having a floor which is level with the bottom of the door (far right of the pic above) out of the question. We're going back to the drawing board with the extension and re-planning the internals with a step up at some point.

Tearing down the extension

The time came to say goodbye to the shoddy, damp, rotten extension last month, which comprised of the Sun Room and downstairs WC. We had long ago ripped out all the internals, but left the structure up to provide some storage space and weather-proofing for the doorway under the stairs.

We've scheduled a builder to join us in mid-June to rebuild almost exactly the same floorplan (properly), so we're doing the prep work in clearing the area in time for that.

You can see below the state of most of the timbers. They had obviously been repurposed when the extension was built in the late 1970s, and in places were nothing more than dust.


The roof had long ago rotted through, and instead of properly re-roofing and repairing the joists, the previous owner had put 18mm ply boards directly on top of the damp, failed old roof - bitumen and all!


The hardest part was removing the incredibly heavy plate glass window and crittal double-doors without leaving smashed glass all over the garden. Having a dog on-site tends to focus one's mind to minimising sharps on the ground, and that's a good thing.


The 18mm, soaking wet ply boards were too heavy for me to lift down from the flat roof, so I set about dismantling the structure from underneath and then sawing through the uprights one by one. When all had been cut, it took a sledgehammer to the corner post to bring the roof down to ground level where I could cut it up.


It took 2 more days to chop up and clear all the old materials from site, and a further day to smash the 15cm thick concrete floor up and remove that. We're keeping that aside as hardcore for the rebuild.


Since the majority of the extension was wood, and skips are expensive, we set about for a 2-day long bonfire on the driveway.