Building our blockwork up to lintel height!

We bought a truck-load of concrete blocks last year, expecting to use most of them getting the wallheads blocked out. That is still a work in progress, so we used the dumper truck to move blocks 40 at a time to the two gable-ends and to all the openings that need squaring up or converting to windows.

We went over the building warrant plans to work out exactly how the damp proof course was to work. We used 90cm DPC, wide enough to cover the full 50cm width of the foundations and to get up and over whichever leaf of blockwork was higher that the other – the inside at a bit above finished floor level, the outside at ground level + 150mm. It was to be bedded in to mortar below and above, then the blockwork on top of that. We had already decided to use cement mortar for the first metre upwards, because it will be tanked on the inside and have DPM painted on the outside. Above 1m, we used lime mortar. The blockwork will still have the liquid DPM painted on, but it will make the wall more breathable into the narrow 25mm cavity between the wall and the timberwork/insulation .This is to help keep the wall dry, not to benefit the living space, which has a vapour barrier just inside the plasterboard.

We tied the blocks into the existing walls every 3-4 courses with Bluebird stainless steel swallow-tail ties. We cut 50cm strips of Expamet expanded stainless steel mesh and bedded these into the mortar at 90 degrees to the blockwork every 4 courses and at approx 1m intervals. These will be tied into the rubble wall when we get to that point.

Geoff worked on the big gable-end, the big opening in the side wall of our garage area and the area between the garage door and front door. Ric worked on the smaller and more fiddly openings. The windows that were doors need to go up to around 700mm or 800mm and already have the quoin stones in place, so will simply need lintels above the blockwork. The new openings, the ones we needed to widen and those that were brick/block lined additionally need blockwork up each side to form the window /door opening.

Geoff & Ric made really good progress and only stopped once they got blocks to lintel height.

New/rebuilt walling

The first of teh blocks we need in the gable-end.

The pilehas grown…

The DPC is in place.

A corner of the gable-end wall is being laid on the DPC,itself beddedonto the slab DPM.

Here is a swall-tail wall tie in place. The tie is screwed into a hole drilled in a granite boulder, the swallow tail is bedded into the mortar.

This is the east edgeof the gable-end wall, showing what was once a door converted into a window.

The gable-end wallheads upwards, teh upper courses are mortared with lime.

This is the gable-end wall at lintel height!

The water supply and the three power cables all in place in what will be the power room.

The bathroom window opening, to be built up 70cm.

The old garage door is to be fully blocked up – it overlooks our neighbours driveway and will have our air sourced heat pump on the other side.

Preparing to rebuild walls

Getting the floor slab in place was quicker than planned, plus my brother Geoff stayed on for three extra days, so we wanted to get on to the next big job – re-building walls. We need to do this so that we can finish raising the wallheads, in preparation for putting a new roof on.

Not having expected to get this far on, we had quite a bit to do before we started laying blocks. For example, with the floor slab in place, we could accurately measure heights over the entire footprint of the steading and compare with the building warrant plans.

New/rebuilt walling

Single-storey wallhead height: So the height from finished floor to wallhead height, on the single storey north wing, will be 2170mm. The architect has specified doors that are 2050mm high, leaving 120mm between the top of the door and the wallhead. All the windows in that section are designed to finish at the same height – 8 openings in total. This is significant. The plans assumed we would have 150mm above doors & windows i.e. we would need decorative lintels because they will show. The best measurements I took before we had a floor slab convinced me there would be no space, so we could get away with structural lintels only.

It is good that we are close to what the architect planned, but it means that granite lintels are back o the list, but we are very short of them. Most that we removed were cracked or were concrete.

Ric suggested that we get what lintels we have and consider sawing them down.

Fortunately we do have one lintel that is long enough to fit over the 1.5m front door opening – it used to be over the old garage opening which is on the way to being blocked off.

Structural lintels

In general we are to use 3 or 4 (depending on the depth of the decorative outer lintel) 100mm wide x 220mm tall reinforced concrete lintels over all our openings. We bought a whole lot of 1500mm and 1800mm lintels months ago, in anticipation, but will need a small number of longer ones.

We looked separately at the garage opening, which is 2440mm wide and needs 200mm bearing either side – around 3m in total. We have no chance of getting a decorative granite lintel that would survive long un-supported. So we looked at steel lintels and discovered the Catnic CM81C model that has the same 100mm x 220mm profile as the concrete ones, plus a 100mm shelf that would support the outward-facing lintel. They are lighter, stronger and probably cheaper than the concrete ones. We found a modification, by the structural engineer, to the architect’s instruction, that show a ‘T’ section Catnic ‘or equal’ for openings over 2m. So it looks as though we should be able to use two of the Catnic lintels back-to-back and make our lives a little bit easier.

New wall profile

All new walling is required to have a 220mm course of concrete blocks on the inside face i.e. standard concrete blocks laid on their sides. This is what we want to work on during this visit. They are to be tied in to existing walling at either end and to have expanded stainless steel mesh strips that will tie in to the granite outer facing. As we build the outer granite, we will first paint a liquid DPM on the outer face of the blockwork – Synthaprufe or equivalent. This will lap down to the damp proof course, on the foundations.

Furthermore the inner face of the whole external wall – blockwork and granite – is to be tanked to 1m height, over a sand-cement render, then horizontally over the concrete slab by 1.5m. The tanking will lap both the DPM from under the floor slab and the DPC. In an effort to improve the breathability of the wall overall, we will use lime mortar in the blockwork above 1m.

A particular challenge with this design is that the granite outer face can only occupy 250 – 300mm depth, yet it needs to integrate completely with the style of building either side of the new stretches. The original walling very clearly was built in courses. Each course had large stones at the base on the outside, held up by a framework of smaller boulders on the inside face of the wall and between the big stones – with lime mortar walls, the stones support each other and the lime mortar stops them moving. A second row of large stones was built over the first one, with some overlap. This was filled then out with smaller & smaller stones until the upper surface was completely horizontal. They repeated this double-banding upwards, spaced to tie in with the various quoin stones.

It looks like we will be spending quite a bit of time splitting our large stones to no more than 250mm depth.

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.

Creating the floor slab – I

We pushed on with our main priority – getting a concrete floor slab in place. A job of many layers…

First, clean up the excavation
We squared up the excavation, clearing bits by hand that the digger could not get to – this was quick, a few hours and barrow-loads for the whole floor area. I spread the trimmings across some of the low areas. We temporarily removed most of the drain pipe we had placed the year before, to make access easier and avoid damaging the pipes. We left the drain for the cloakroom area in the north wing, because it only stuck out by a metre or so, and the deep drain in the bathroom area in the west wing, because it was still (just) buried in the subsoil.

1 – Hardcore
Next up was the 200mm layer of hardcore. We started in the garage area because it was easy access and small. It would also let us access the master bedroom area beyond. Ric used the digger to load the dumper and drop the hardcore in the area we were working. I spread and levelled the hardcore, working from the back of the area towards the entrance. The hardcore is brutal stuff and was a pain to work with. It includes hefty lumps of broken concrete/stone up to 15cm long and the matrix looked like a mix of smaller broken concrete/stone and quarry dust. The big stones seemed to ‘float’ to the surface when dropped from the dumper, I spent a disproportionate amount of time and energy shovelling or throwing them by hand into the un-filled areas. I spread it by eye, trying to get it 5cm or so above the compacted level we needed. It got easier with a bit of practice, eventually I had no problem getting a decent regular surface with no more that 3-4 cm difference in height over the area. We filled the area then used the wacker plate to compact it. That worked a treat. After four runs – along, across, along and across – it compacted down the expected 50mm and had all locked solid.

We built a ramp of hardcore to get the dumper truck in and out – 6 dumper loads. We left the long sides clear of hardcore to form troughs along the edges, about 50cm wide at the top and 20cm at the bottom. These will fill with concrete, to thicken the slab as per the architects design – to support the structural timberwork that will hold our floor joists up. We did not bother in the places we had already laid foundations, these will support the slab directly. We cleared the hardcore ramp into a space we had left, compacted the whole lot and that was job done. We put the pipes back in and had to use pickaxes to break up the compacted hardcore, a couple of hours of hard labour. Lesson learnt – we will put the pipes back in place before compacting!

The following day, Ric built hardcore ramps to get access to the long north wing and the east wing. Then it was a lot more of the same – empty a dumper-load, pick out the big stones on the surface and drop them out of harms way, level with a shovel and, when the area was filled, compact it.

In the north wing we needed to complete the pipe that will feed air to our woodburner – I had run the pipe under the wall from the outside but could not finish it because there was a pile of spoil inside. Ric had uncovered the end of it when he excavated the subsoil out, it projected about 50mm into the floor space so that it will be easy to get at, to finish off. I waited until we got the run of hardcore right up to the pipework, connected a pipe to halfway across the floor and put an upright on the end of that. We dumped the next loads of hardcore right on top of the pipe, then carried on as normal.

In the east wing, we left the long edges clear of hardcore, to form the troughs for thickening the floor slab, just as we did at the west end.

After three days work, we had all 230 square metres covered in hardcore and compacted. We had used 110 of our 180 tonnes of hardcore, more that I estimated, but we are not short of the stuff. I guess we had over-dug some areas e.g. because of obstructions.

Floor slabs

We did the garage area first, it is a bit rough because of the large stones on the top.

We ran this ramp from the garage area to the master bedroom area.

We used a broken scaffold board for the run up

Adn another load makes its way.

We levelled out the ramp at the end.

We got a flatter surface this time around.

We used a pick-axe to re-lay the drain pipes – slow work

We are making inroads into our hardcore piles!

In the long run in the north wing, the cloakroom drain pipe is currently above the base level and will just be covered by the hardcore

The drain is safely under hardcore

We put pea gravel around the drain pipes

We got teh best finish so far…

And this is the wacker, amazingly effective.

The last area to do, the east wing.

Annoyingly, this pipe is partyl above hardcore level.

And the last of the wacker-work!

2 – Running services through the floor slab
We had already laid two armoured electrical cables, originating in the plant room area, near the future front door. They both run through the master bedroom area and into the south run of drain trenches. One is for the bothy and diverts off and (temporarily) above ground under the caravan. The second carries on all the way beyond the septic tank, where it will power the pump for our raised drainage mound. We have also laid a 20mm blue water pipe alongside the cable that runs to the bothy. It too starts its journey in the plant room, where the rising main will appear above concrete. This pipe is in use as our temporary water supply to the caravan, we will run the pipe and cable into the bothy once the caravan is finished with.

We want to lay a third electrical cable, for our polytunnel. It will run from the plant room, along the full length of the north wing and across the west wing to our family bathroom area, where it needs to exit the building on the east side through the foundation opening.  We are burying all the cables and the pipe in the blinding layer, above the hardcore and  below the damp proof membrane.

We did one other job at this point, testing the reinstated drains for leaks. We bunged up one end of each pipe at the inspection chamber, filled the pipe  with water and left it for ages to see if the level dropped. They did not, they all passed with flying colours.

The electric cable for the polytunnel is laid on the hardcore before the blinding.

The water supply and the three power cables all in place in what will be the power room.

3 – Blinding
The 50mm of blinding helps level the surface and protects the damp proof membrane from being punctured by stones in the hardcore. On advice from our builders merchants, we got 20 tonnes of quarry dust delivered. This is more gritty than the sand I was expecting to use and compacts well. Plus it is half the cost. We divided the floor area up into equal-sized segments and put a dumper-load – a tonne or so – in each segment. We raked it out roughly level then used a home-made screeding rake to level it out and compact it. This was one of our short, fat, kwikstage scaffold boards on its side, with a handle attached. We even put a spirit level on it to work out when the blinding was levelled. The tool was surprisingly solid and heavy and using it was hard and slow work, but after enough runs across at different angles, it produced a very flat, compact, smooth finish. We finished off with a single run of the wacker plate for good measure. We used a couple of extra dumper loads to line the edges and bases of the troughs we had left in the east and west wings. The three electricity cables and one water pipe were duly buried. They all come up together out of the blinding, cable-tied together, in a corner of the plant room area.

We spread the piles of quarry dust evenly over the hardcore

We got a pretty good level surface.

We did a single run with the wacker.

It was a comparatively quick and easy job.

The east wing was slower to sort out because of the foundation blockwork and the drain pipes.

We lined the troughs at teh sides of the east and west wings (to thicken the floor slabs).

This is our screed rake, made from a scaffold board. Note the spirit level!

The most troublesome area…

4 – Expansion joint
We are required to put an isolation joint round the perimeters of all the slabs, to accommodate expansion of the slab. I used 13mm bitumen board, which is a soft fibreboard that I could cut with a Stanley knife, but which went quite floppy in the rain. I cut the boards into strips – 17cm wide (7 per board) for most of the perimeter and 40cm  (3 per board) in the troughs. It was my least-favourite job to date – slow and too much bending, standing & kneeling. We ran the board into our doorways and the various nooks & crannies in our walls. The positive in all this is that the damp proof membrane will be protected from sharp edges in our walls.

The strips of expansion board in teh troughs were 40cm deep.

Elsewhere they were 17-18cm.

5 – Damp Proof Membrane (DPM)
We used 1200 gauge (300 micron) polythene DPM in standard 4m x 25m rolls. We always worked across the floor area between outside walls, using PVC single-sided tape to seal the 400mm overlaps. We did not bother with the double-sided tape we had planned to use. The open areas were easy. Where we had a pipe coming up, we cut a slit, dropped the membrane over the pipe, then cut a small square of membrane that we cut accurately to the diameter of the pipe, slid down and securely taped to both pipe and membrane. It was a lot more tricky sorting out the various door recesses and the troughs. We had to cut and patch it a lot – a sort of giant craft activity. The tape was very effective, even on damp membrane, but was not so good when rain puddled up. I also found by experience that DPM is not the thing to do on a breezy day – at one point I had to give up and wait until the wind died away.

A slow start!

We used a couple of sheets of mesh to stop the DPM being blown around. We overlapps the lengths of DPM by c. 40cm.

We cut out sqaures of membrane to push down over drain uprights, then taped then securely in place.

Most of the garage area was covered in one length of membrane!

We ran the DPM up onto the foundation blocks and taped them down.

6 – Reinforcing mesh
The last job before we got the concrete mixers in was to lay the reinforcing mesh. We used 8mm A252 panels 3.6m x 2m on 70mm supports. This in theory gives us at least the required 25mm of cover over the mesh, even where the mesh panels overlap. We made slow and steady progress, working through a handful of 9” angle-grinder disks cutting the panels to allow for pipes and recesses. Moving the panels into place was definitely a two-person job, it was too easy to catch the membrane and make holes in it. We overlapped the panels by 30cm and wired them together – using a twizzler device to wind the wires and tighten them. It was all solid enough to walk on. The most awkward bit was where one of our pipes gradually sloped up above the blinding and up to mesh height. I cut out a couple of small panels of mesh and used a sledge hammer to form them into curved up-stands that went over the pipe and were tied to the mesh either side. Hopefully there will be enough depth of concrete that they will be covered!

The mesh is in place in the west wing…

We used teh angle grinder to cut the mesh and wired the sheets together with a 30cm overlap.

The long run in the north wing, ready for concrete.

The west end ready as well.

I used a sledge hammer to bend this sheet of mesh over the raised drain pipe.

We hung mesh down into the troughs to further reinforce them.

Excavating our floor

How not to travel
We headed up to Aberdeen, for our last block of work for 2017, with a cunning plan: To drive half-way the night before, stop overnight and get to the steading early enough next day that we could get something useful done as soon as we arrived. We had booked in at the Chester-le-Street Travelodge, expecting to get there around 10.30pm.

It was all a mistake – motorway maintenance now all appears to be done at night. We got to the A1 and up just beyond Elkesley, to find the A1 closed. We diverted on the A57 across to Sheffield and the M1. Shortly after we saw signs that the M1 was closed somewhere near Barnsley. So we followed a slow diversion to the following junction, getting back on the M1. Up at Leeds, the M1 was again closed. The diversion was through parts of the city centre and at one point we got onto the south-bound diversion, ending up back at the M1 before the closure. Second time around, we took executive action, ignored the signs and worked our way across to the A1. We were not done yet – the long stretch of A1 from Leeming Bar to Caterick was also closed, we diverted across to the A19 and up to Stockton, getting back to the A1 a couple of junctions before Chester-le-Street – two and a half hours late.

The following day was much better, we got to the Edinburgh city bypass without mishap and, with a couple of wrong turnings, to the M9 and Linlithgow. Which is a lovely old town, with the ruins of the palace just off the main street. We found our lime shop and half an hour later were re-arranging the contents of the car to get 8 bags of Singleton & Birch NHL 3.5 lime in beside the dog. Given the extra 200kg, we took it easy and got to the steading around 3.30pm. It was raining heavily when we arrived, so we caught up with what Ric had been up to over the week. Which was a lot.

Excavating the floors

He had dug out all the floors of the steading to the required 53/55cm below finished floor level, apart from the garage area, which will not have insulation and screed, so needed to be 40cm below finished floor level. The holes looked deep, dark and huge, more like we were digging out swimming pools. Also the courtyard that Ric had spent a week or so clearing earlier in the year was full again – all a bit off-putting. As we well knew we would, we had exposed up to 300mm of the soil below our stone walls – they have minimal foundations. This will be sorted out with the hardcore and concrete, but it was a bit scary seeing the walls unsupported for the next week.

Floor slabs

Ric had done a pretty good job scraping out the base for the slab – just a few barrow loads to square up the edges.

The foundation concrete will finally disappear out of sight…