Over budget & behind schedule

Foundations and drains – way over budget and running late…

The last few months have been a bit of a roller-coaster for us. We have got masses done, but my estimating has broken down quite seriously. The plan was to get foundations done comfortably in July and complete both sets of drains in September. Here we are, with foundations spilling over into September and a half-completed surface water drainage system. We have gone around £2,500 over budget with more to come to finish the job. The full cost may easily be double the estimate by the time we finish.

My concern is mostly cost. The time delays are annoying, but we do not cost our time, and it does not matter if we take weeks or months longer to get finished. It does matter if Ric is spending his time on lower grade work like digging trenches – we need him doing the planning, complex stuff, applying his specialist knowledge and transferring skills.

Trying to tease out what went pear-shaped:

• I estimated costs for materials based on ideal trenches. Our ground was quite a bit more bouldery that I expected based on when George dug our fencing strainer posts. Mechanical digging was slower and trenches wider and deeper, so we used (much) more digger time and materials than estimated.
• I had not estimated the time needed to hand-dig foundations at all well, it took longer than estimated.
• It took longer than expected to break through our hardstanding.
• I underestimated the amount of pipe, the number of fittings and their costs.

Ric took the pragmatic view that anything involving digging into the ground was quite unpredictable, so was not fazed. Anecdotally other people have said the same.

How good are my estimates (in general?)

Out of 50 completed tasks on my plan, 4 incurred no costs, 28 came out under-budget, so 8 went over-budget. My notional ‘savings’ for under-budget tasks are around £13k, the notional ‘losses’ are around £5k, I am still nearly £8k underspent on £154k spend to date (includes purchase). Twelve tasks were within 10% of estimate, 15 are more than 25% out. None are more than 100% out, yet!

Following my miscalculations, I reworked all tasks involving groundworks, including landscaping and handling spoil.  I used experience to date to allow sufficient digger/dumper time and materials. Unsurprisingly this has increased the cost of completing the whole project, but not outside my ‘expected’ upper and lower limits.

Foul drains

Our building warrant spends little time talking about drains, but they are one of the things Building Standards want to see before they disappear under ground.

Our steading is not compact, plus we insisted on having bathrooms in east and west stretches, so our drain plan is not simple. Where possible the architect runs internal drains outside under existing openings. All drains leaving the steading connect to inspection chambers along the main run of drain.

North run: So we need a drain that runs along the north of the property from our front door to take waste from upstairs en-suites at each end of the building. It also takes waste from a cloakroom and the kitchen. It does a 90 degree turn southwards at the north-east corner and takes waste from our main bathroom.

South run: A second length of drain is to run along the south side, starting with our master en-suite in the west stretch, It is to run straight across from west wing to east wing, with a branch off to our bothy (to be connected at some point in the future). In meantime we will use that for the caravan. It is to join the north run at an inspection chamber then run downhill and to wards the boundary to the septic tank, but not closer than 5m from the boundary.

The septic tank & beyond: The effluent from the septic tank is to be held in a storage chamber just south of the tank, to be pumped at intervals up to our raised mound soakaway positioned west of the pump station. We will build the pumphouse and raised mound later.

Good to go: We ordered large amounts of brown drain & fittings, inspection chambers, 20 tonnes of pea gravel and a 3750l septic tank, with neck extension.

Trenches: Ric started digging the trenches whilst we finished the foundations. He opened up the southern run first, then up the east side and northern sides. We positioned the trenches a safe distance from the steading foundations, but well away from where vehicles will run – never closer than 1m – 2m from the steading boundary wall. Once we had finished foundations, we levelled the bottoms of the trenches out and laid pea gravel to get the required 1:40 slope. We hit all sorts of niggling issues including poor bouldery ground (a lot more wider/deeper trenches than we wanted), the water table being higher than the lowest points of the trenches and large amounts of high quality hardstanding to break through. We made slow progress and we had to head home, leaving Ric on his own to plug on. Just before we left, I had contacted Building Standards to arrange a visit date. We got a reply back saying one of the two inspectors was on leave and take photos and submit them instead.

Ric did make impressive progress. He put inspection chambers at every point where a drain entered the system. At the (shallow) starts of the runs we used 350mm inspection chambers. As the drain got deeper, we used 450mm chambers. Fortunately we had got to the point where north & south runs joined and could just get away with a standard chamber – any deeper and we would have been constructing more complex/expensive solutions. Having placed the drain pipes and connected the fittings, he put gravel up to the top of the drain pipe, photographed it and left it.

Running drains out from the steading: The master bedroom en-suite has two drains that run through the gable-end foundation, under lintels into the start of the south run. The drain that will serve the west wing upstairs en-suite runs through the front-door foundation into the north run, as do the two pipes from the family bathroom area. One of the latter, which also serves the east wing upstairs en-suite, runs through the foundation for the bathroom window. All easy to set up and they run straight out into inspection chambers.

The second bathroom pipe and the drain for the cloakroom area near the front door do not have nearby foundations, so needed the less-easy option: digging down under the foundations.

The cloakroom pipe is shallow because it is near the start of the north run, we dug a hole 50cm wide and 50cm deep immediately below the base of the wall, from both sides. To support the wall, we poured a 200mm pad of concrete in the base, laid concrete blocks each side up towards the blocks, then placed five lintels across the blocks, leaving a narrow space above. Finally, we pushed dry-ish mortar into the gap. Job done. The second bathroom drain was more demanding because the inspection chamber was a metre down. No different really to the cloakroom drain, but lots more digging. We put the lintels just above the drain and laid blockwork up to the base of the wall and pushed the mortar in to fill the gap.

So the bathroom inspection chamber has a low pipe than leaves the building at the level of the inspection chamber base and a high one through the foundation. We created a backdrop – a vertical length of pipe – to get the high drain down to the right depth.

Installing the septic tank: We arranged with George to spend a day digging the hole for the septic tank and the effluent pump. Because the water table is high-ish, they had to part-fill the tank with water after it was dropped in to the hole. The first attempt failed because having left the hose pipe in the tank to fill, he did not notice that it had a stop-end. The water level in the hole rose and the tank duly erupted from the ground. The second attempt worked.

Ric temporarily ran the effluent drain to our convenient concrete sump at the bottom of the plot.

Connecting the caravan! As part of the block of work, Ric installed a drain from the inspection chamber that will serve the bothy and ran it up into the caravan toilet. It feels so civilised being able to use an indoor toilet rather than the composting toilet in the bothy! And that was about it for the foul drains, at present. He aimed to use the same trenches for our surface water drains.