Creating the floor slab – II

The Plan
We had booked our concrete over three consecutive mornings. I went with the volumetric mixing trucks because they have up to 6m of reach from the back of the truck and because they can hold 9+ cubic m of materials, however the trucks are 8m long, much bigger than barrel mixers, so we had to do some rearranging on site to give them access. The first day we would fill the garage and master bedroom areas in the west wing, with one load, estimated 7.6 cu m. The following day we would use two loads to fill the north wing, estimated 14 cu m. Then on the third day, do the east wing, estimated 7.6 cu m.

The Reality
We used more concrete that I expected: My estimates were bad, I had assumed a dead-level blinded surface and exactly 125mm depth of concrete. There was a few cm variation within each discrete area (master bedroom & garage in the east wing, the north wing and the east wing) and some variation between them. So the garage area base was not exactly 15cm higher than any of the other areas. These differences were significant. If the north wing, for example, was just 1cm lower than it should be relative to the other areas, we would need almost one extra cubic metre of concrete. My other mistake was to assume that the extra volume to fill the troughs (along the sides of the east & west wings, to support structural timber) were to be spread evenly across all the floor area.They were not. So I particularly underestimated the amount of concrete for the east and west wings.

Both my brothers told me, after the event, that I should have added 10% to my estimate and ordered 33 cubic metres.

Day 1
Anyway, the truck turned up on the first day. We got him to pull up in next-door’s driveway and back up to the master bedroom area. We had parted our fence, so the truck could get as close as possible: We will patch it up once the job is done. It went very smoothly. The concrete was set up for a C35 mix and was fairly runny and well-mixed, so flowed easily. By adjusting the number of chutes on the end of the mixing auger and the direction of the auger, we really did not have much raking to do. My youngest brother, Geoff, did the skilled work. He had a laser level that stood at one end of the area and a receiver that he fixed at the right height on his tamping tool. If the tool was low, it made rapid beeps, when too high, it made slow beeps. When it was at the required level it made a continuous tone. So with a minimum of fuss we got the master-bedroom area filled.

It had used at least a cubic m more that I had estimated and the driver thought he did not have enough materials to fill the garage area, so we rescheduled for a separate job over a fourth day. This was annoying, but not disastrous. Geoff used his concrete roller to push the aggregate down, then his float at intervals to smooth out the surface. It rained, but we still got a good surface.

Floor slabs

We cut our fence to let the truck back right up to the steading building

The chute went right to the middle of the master bedroom area

Geoff used the roller to push the aggregate down out of site, then this float to polish the surface

It rained, so the wet concrete is partly underwater

But the water does not seem to damage the finish

Our dog, Misty, escaped at one point and left her mark…

Day 2
The following day a different driver turned up with a smaller truck. he backed up to what will be our garage door and filled the garage area. We opted for a stiffer mix, which was bit more work, but should allow a better finish, since it is the final surface (no insulation or screed on top).

Annoyingly it rained more heavily than the previous day, but again Geoff got a good smooth finish. Ric spent part of the day clearing lintels and granite out of the way so the truck could back up next day to the north wing through two openings.

Ric built up the access to the garage area with hardcore to allow twh truck to get as close as possible

This is a itlle truck compared to yesterday

Raking the concrete to the edges

Another excellent finish from Geoff

Day 3
We got the first truck load in the west half of the north wing and got the full 9 cubic m. We were a bit concerned about whether we had got the area more or less that half-filled. We also had to get the concrete spread over a longer distance. Ric constructed a separate chute from a sheet of galvanised steel on a wooden frame and, when the truck reappeared an hour and a half after leaving, it worked perfectly. As it happened, we used 6 cubic m from the second load – I think the floor must have been, on average, a bit higher here.

The galvanised sheet on the chute came out looking polished and shiny – just like new. Was this the abrasive action of the flowing concrete, or a chemical thing?

At one point the driver did say he would had enough concrete on the first day to finish the garage area, after all. Hey ho!

Geoff spreading the concrete delivered down Ric’s home-made concrete chute!

The chute in all it’s glory

Geoff polishing the surface!

The end-result

90 square metres of concrete…

Our water supply pipe finally fixed in place by 125mm of C35 concrete!

Day 4
On the final day, the driver loaded a full 10 cubic m of material on the truck, got it backed up to the bathroom window area and, with Ric’s chute, got the whole area filled with one load. Just. There was about a bucket of mix left over. It rained again and Geoff worked a smooth surface under water.

Geoff working his magic on the west wing floor

We used 33 cubic m of concrete in total – my estimate of 30 illustrated exactly why I needed to have used the ‘add 10%’ convention. Laying concrete is stressful because of what can go wrong and the difficulties with correcting mistakes. Aberdeen Concrete ltd made it much easier than it could have been. They were helpful and we only paid for the concrete we needed. But we were all relieved once the last load went in. We did have to clear quite a lot of space to allow their trucks to get backed into the opening we wanted to use.

Having spent the last three years climbing about inside the steading, it is quite strange walking on a flat, hard, continuous surface. The drain pipes look much more professionally installed now they poke vertically out of the concrete and it is blessing not to be tripping over the external electrical cables and water supply. We know from the puddles on the concrete that the surface varies by less than 1cm over each area. It will be a good base for the insulation panels and screed.

Concrete & Lime

Concrete

I have discovered the complicated world of ready-mix concrete. We need around 30 ‘cubes’ and want delivery trucks with elevators at the back end, so we can get the stuff within the steading walls before barrowing it i.e. no more than 10m to push each barrow load.

I looked around, there are loads of companies in and around Peterhead and Fraserburgh. I checked out a reasonable sample, none do trucks with elevators. By chance I looked nearer Aberdeen and spotted one that did on-site mixing, which I knew nothing about. I glanced at their website and Lo! They had a piccie of a truck with an elevator and a chute, that would reach up to 6m from the back end of the truck. I phoned them, they can deliver when we want it, it will take 3 loads of one of their trucks, we can have one or two trucks relaying the materials to our site. Perfect. The price, £115 inc vat per cu m, is also not bad.

It turns out the company uses ‘volumetric mixing’ trucks. They have hoppers for sand, gravel & cement plus a tank for water. They mix on site by metering materials onto a conveyor belt and into an auger screw, add the water, then the screw mixes the concrete and pushes it out into the chute. Fine by me. I texted my two builder brothers and got suspicious replies. One said he tried it years ago and did not like it because it did not mix as well as a normal barrel truck. The other asked dubiously whether they would certify their mix.

I did some due diligence on Google and discovered that the industry is ‘somewhat’ divided about volumetric mixing. In the pro camp, they all say that you only get and pay for exactly what you need, there is no transport time for it to go off, it is cheaper because the trucks can do several drops in one round trip, they can alter the mix at any time. Nothing about the quality of mixing, though. The anti camp say that it is lower quality, but also that it is unfair because the volumetric trucks are classed as ‘engineering’ vehicles not HGVs, so they pay less road tax, do not need operators licences and do not need to meet upper weight limits for their vehicles. A fully loaded volumetric truck can mix 10 cu m in one load and weighs in at around 40 tonnes. Some-one suggested that if the trucks had to meet HGV weight limits, they could carry enough materials for about 4 cu m, so they would not be economic. And so on. The debate is heated.

I checked with our architect, he said we did not need a certificate for the concrete.

A question for another day, “how hands-off can you be and still get decent quality housing stock?”

I found some US technical documents about the relative qualities of volumetric v weight batched concrete. If the equipment is set up correctly and the operative knows what they are doing, they found that volumetric concrete was marginally stronger than barrel or drum mixed. So, what to do? Actually, it was an easy decision, the plusses greatly outweigh the minuses. The mix they quoted for, C35, is so massively over the top for a floor slab that it would have to be wildly variable to cause us future problems. So I will phone them and give them the opportunity to show their expertise and customer service. At a not-bad price.

Lime

We have found a source of lime that we will go with. In principle we want to match our mortar to what was used when the steading was built, but that may well have been produced from local materials that we do not have access to. Possibly sea shells. Or that rare outcrop of limestone up the coast towards Boddam. Who knows? We also observe that the walls in east and west wings are substantially tougher than those in the north wing, but is that because the builders used more mortar or a different composition?

So, to be practical, we looked for a commercial medium-strength naturally-hydraulic lime (NHL 3.5) that we knew we would be able to get hold of in large enough quantities, over several years. There are several candidates, so we looked at a) availability in Aberdeenshire and b) cost. Our local builders merchant sells a brand of lime, but it is over £17 per 25kg bag ex vat. Looking at on-line suppliers, their per-bag costs are lower, but by the time you add in transport, it is up to that sort of level. We kept looking until we found Singleton-Birch. They are based in the Lincolnshire wolds near Louth – close to where I was brought up – but have a stockist in Linlithgow, a stone-throw from the Forth bridges. I will drop in on our way up to Aberdeen and get 8 bags or so, at £11 + Vat a bag. If it is what we want, they will deliver tonne pallets to the steading for around £13.75 inc VAT per bag.

Lime goes off quite quickly, in the way cement does. I will take a whole load of heavy-gauge plastic bags (that we get out dog food delivered in) to wrap them up. We will see if that extends their life enough to work through a tonne batch.

Our next challenge is finding a consistent sharp sand to go with the lime, that resembles the original mix. We will start with the local stuff, which comes from a local quarry the far side of Ellon – recommended by the architect.

Finishing foundations

Finishing the block work: We carried on where Ric left off in July. I learned how to lay blockwork and finished off all the short stretches. I was slow and messy, but the end result was quite acceptable. I used the level to get the inner-leaf heights right for finished slab level and used the angle grinder to cut the blocks. Once Ric was back up, we worked on the blockwork for the inner foundations, measuring up pretty accurately against the plans to make sure that they snaked exactly where they should – to support stairs and structural timber for roof trusses & garage.

More concreting: We needed to pour concrete around the blockwork to finish the foundations off. Those for windows have the two leaves of blockwork. We filled the gap with weak concrete (half the cement compared to the C35 foundation mix). For doors and windows, we then filled the inside edges to 30cm from finished slab level – they will directly support the slab. We filled the outside edges  of the door foundations to slightly below finished ground level, to support doorsteps.

Having got the short stretches done, we tackled the gable-end foundation. Deeper and wider than we wanted, because of the rough going digging it, it was a comparatively big job. We filled up to the level of the openings for drains. Once it had gone off, we blocked and lintelled the openings, then topped the concrete up to final level.

The internal foundations were fairly quick, just levelling up either side of the block work to the 30cm below finished slab level.

Finishing the foundations was a definite achievement – the first visible signs that we are heading upwards.

Laying Foundations

We got all our foundation trenches dug out then moved on to pouring the concrete.

Cutting the mesh & setting depth markers: Ric cut up the rebar mesh ahead of time. He then cut lengths of rebar rod into c. 30cm lengths, to use as pins to mark the levels of the tops of each foundation. The short trenches needed a single pin, knocked in leave just 200mm exposed.

In the longer trenches we used the level & staff to find the highest point and knocked in a pin with 200mm exposed. We used the level to set the other pins along the trench at the same level. There was  no more than 5cm or so of variation in the base of the trench, not bad considering the rough going.

Mixing concrete: We worked out that C35 concrete required one bag of cement to 4.75 builders buckets of block mix, yielding two barrows of concrete. We spent several solid days mixing concrete: Jill filling the buckets; me/Ric chucking them into the mixer with the cement & water (some water, two buckets blockmix, the bag of cement, the remaining block mix, more water); me running the barrows to the trenches. Access to the maze of trenches was indeed a problem, we bought some long scaffolding boards to set up runs over trenches and obstacles.

Pouring concrete: We did the short trenches first, barrowing c. 75mm of concrete into each trench, used our patented wooden tamper to get air bubbles out and to level the tops and dropped the rebar mesh on top. Then more concrete on top until level with the rebar pins and using the tamper to level it off nicely. We ran out of blockmix, ordered more and carried on.

The gable-end trench: We did the gable-end trench next. We had temporarily diverted the water in the damaged clay pipes onto some guttering, caulked with clay, to allow us to finish the trench. We ran concrete under and up the sides of it, dropped in the mesh, then used rather stiffer concrete to build up either side without collapsing into the gutter and blocking it. The rest of the trench was as normal. The end result was 8m of foundation all within a cm or so of horizontal.

We filled the internal foundations just about in time for myself & Jill to head back down south.

Taming the Wilderness

The land attached to the East Byreleask Steading is former farmyard, slightly over 3/4 acres, 0.3 hectares. There is very little in the way of farm buildings remaining, but it is still a challenge.

Concrete: We have quite a bit of concrete…

1. The concrete bases of former farm buildings, hardstanding and the floor of the silage clamp amount to about 700 square metres of concrete. Assuming it is 10cm thick on average, that is 70 cubic metres or 170 tonnes.
2. There is around 80 metres of concrete wall that is 50cm thick and 2 metres high. This is an additional 80 cubic metres or 190 tonnes.
3. The floors of the steading amount to about 210 square metres. Assuming it is 10cm thick on average, that is 21 cubic metres or 50 tonnes.

Whilst concrete is just as typical of traditional Scottish farming as granite steadings, there is mercifully no planning requirement to preserve it as part of the built environment! I hope the walls can be knocked down by our digger man. I will buy a concrete breaker to get the concrete slab into handle-able chunks. What do we do with 400+ tonnes of broken concrete? We will hire a crusher and break it to hardcore. We can use it within the steading floors and to build up the shared track – all 470 metres of it, probably. The alternative would be pay to remove the waste, then pay again to get the hardcore we need for the building works.

Whilst the cleared areas around the steading will be building site for a few years, we will want to get the rest of it restored to garden. Given this will take years, we need to start sooner not later. We have yet to find a source of manure of other organic waste, but have started our first compost heap.

Track: The ground between the steading proper and our out-building is a well established farm track and runs across much of the plot. Assuming we will also want to convert this to viable garden, we will probably need to dig it out, remove the hardcore and start to build up the fertility.

Jungle: On our visits to the site before we owned it, we could not see from one end of the plot to the other. There are a number of mature ash and sycamore trees but everything around and between them is overgrown with smaller trees and perennial weeds, especially nettles. There is a good deal of concrete and stone scattered around. A strip down the eastern side is rough grass.

During our September visit, we found time to clear a small area. We removed some smaller trees, mostly sick-looking elder. We cut branches from two of the mature trees to above head height. The effect was immediate – a much more open wooded area that we could access. We will need to tackle the perennial weeds over several seasons – we have asked for a petrol strimmer for Christmas.

Japanese Knotweed: During our September visit, we came upon a patch of not un-attractive bamboo-like fronds, with somewhat heart-shaped leaves. It meant nothing to me, but Jill was suspicious. Back at her parents house, she confirmed that we had Japanese Knotweed on site. Reading up about it, it is a real nuisance. It is invasive and the roots can break concrete. It grows rhizomes out and down for several metres and small fragments of broken rhizome will quickly grow into new plants. Whilst it is not notifiable, we are required to make sure it does not invade anyone-else’s property and must not sell the property without informing the buyer. It is a headache for commercial builders, where time is of the essence. If you only have months to work on a site and sell it, you more or less have to excavate several metres down, sieve root material out and burn it. We have more leeway. By regularly using glyphosate on the foliage, over at least three years, it should eventually weaken and die.

Fortunately, this was the best time of year to treat it, whilst it is flowering. We bought weedkiller and sprayed the patch we had uncovered. We delved further and found more. Then more. Then more. We ran out of weedkiller, bought more and carried on. Much of it was too tall to spray, I cut it at ground level and we later burnt it. A month later, most of the sprayed foliage had died and there was some regrowth, this should not survive winter. We did read that the new growth can be cut, steamed and eaten. We will be working on destroying it for the next few years.

In November 2014 this headline, from the Independent, was typical of a minor feeding frenzy – “Japanese Knotweed: Government to issue Asbos (Anti-social behaviour orders) to those who fail to deal with invasive plant“. Here is the article in full…

“People who fail to control the growth of Britain’s most invasive and pernicious alien plant species could be issued with anti-social behaviour orders (Asbos), the Home Office has said.
The Government has named Japanese knotweed as one of the “non-native” plants which “have the ability to spread and pose serious threats to biodiversity, the economy and human health”.
As a result, new rules have been introduced in the Anti-social Behaviour, Crime and Policing Act 2014 that could see people and organisations served with notices for “not controlling Japanese knotweed [when they] could be reasonably expected to do so”.
“Failure to act” is defined specifically as a form of anti-social “conduct”, according to a Home Office document, and individuals could be fined up to £2,500. Companies who allow the weed to get out of control could face a fine up to £20,000.
Japanese knotweed was brought to Britain in the 19th century as Fallopia japonica, a medal-winning ornamental plant.
But it has become a botanical menace, capable of ripping through concrete and brickwork and causing £170 million of damage a year.
Just a few millimetres of its underground root or rhizome is sufficient to spawn a new plant, making its removal from soil time-consuming and expensive – getting rid of it from 10 acres of the London Olympics site reportedly cost more than £70 million.
The new powers come after trials have raised hopes that psyllids could prey naturally on the plant, and in doing so diminish its ability to spread so vigorously. The targeted introduction of the specially-bred insects for trials was the first time the release of an alien insect species had been authorised in the EU.”