Focus on Foundations

This week has been all about the foundations. A five-tonne digger and three-tonne dumper truck were hired for excavations. We’re working on a 48hr notice with building control for sign off at the necessary stages of the build, so our initial requirement is to dig a first trench, 1m deep, for the builder inspector to sign off on the depth of the footings for the extension. As we’re putting in a block and beam flooring, rather than an oversite system, we’ve actually gone down 1.2m so this should more than suffice. What’s more, going down 1.2m we went beyond the clay and hit flint which is about as solid a surface as you’ll get.

I challenged Mac on why he’s putting in block and beam flooring rather than an oversite system. Not because I doubt his building decisions in any way, but more for my own understanding and to share his reasoning.

I’m well informed that block and beam flooring is always his preference as you can build it one go and then it’s finished without the mess and dirt that comes with an oversite system. In his view there is also less room for errors by the various trades further down the line. As the beams are put in, to the required measurements, with door openings and the likes all set up, the house layout is very clear for the subsequent bricklaying team. The block and beam is set 180mm below the finished floor level, allowing for the underfloor heating above that. It’s neater, quicker, cleaner and a more organised system, paving the way for the subsequent work, and can be brushed clean at the end of the day to leave a tidy site. With an oversite system, and the concrete and type one that comes with it, there would be mess for a lot longer. And let’s face it, Mac doesn’t like untidiness so the block and beam floor also pampers to his OCD!

With the initial trench dug, the building inspector was called and came out within the hour. He was more than happy with the depth of the footings, given no surrounding trees, the hard flint surface and our depth of 1.2m. The footings of the existing house were also proved and the structural engineer likewise happy with this relative to the truss roof we’ll be putting over the whole house. So we’re given the green light to proceed on this depth basis and agreed the building inspector will return again the following day once all the footings are all dug.

With footings dug, we’re now bottoming out – essentially getting our hands dirty and manually shovelling out the remaining soil and debris at the base of the footings so the bottom of the trenches are left clean and smooth to ensure a firm and even base when the concrete is poured.

The extension and new foundations go across the back of the house, as well as a section coming out at the front right side of the house to level it off across the front.

A second positive site visit from the building inspector signs off the footings in their entirety.

With footings dug and a smooth, clean and solid base left at the bottom, we’re now ready to pour the concrete.

Building control are then called and make their third site visit of the week to sign off on the completed foundations. Onwards and upwards!

A note of warning from Mac regarding the footings. This is one of the most important stages of the build. If you don’t get this right it can be very costly to fix at a later date. Be very sure yourself that the footings have been dug to the correct required depth throughout. Sign off is required on the depth, proved from initial trench dig, and then again on the poured concrete. A cowboy builder that is trying to save money may well get sign off on the initial trench depth, but then cut corners on the remaining footings and not dig the rest of the footings to the depth required – excavating and removing soil can be costly. So be very sure you’ve got a trusted, reputable builder for your foundations else check them yourself too. Sadly, we’ve heard several horror stories where footings were not completed to the depth required, but then hidden up with the concrete pouring, and those house owners have movement and other knock-on effect issues with their build. So be sure to get the building inspector to sign off the completed footings, from a site visit, before concrete is poured. Even be there during the inspector’s visit so you can hear for yourself that all your footings are to the depth required. You will sleep a lot better at night in the knowledge that your foundations are sound!

Ordinarily with footings poured, we’d then be looking to crack on with the block and beam flooring, but we’re going to spend a couple of days first on the landscaping. Think ahead and think smart! Whilst we’ve got the digger and dumper truck hired, it makes sense to prepare the rest of the land for any future landscaping. Let’s get all the muck and hardcore cleared off site early in the process too. We’re going to be putting a patio down at the back and improving the front driveway, so we’ll spend Monday and Tuesday next week scraping the land back by 10 inches ready to top soil and turf.

Follow us next week as we progress this and make a start with the build.

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