For the last year Rachel has been in the process of building an extension to her home in Sheffield. The project is a self-build project being constructed as much as possible by Rachel and her partner, Ross, over holidays, evening and weekends. As the extension becomes watertight, Rachel reflects on the process of building so far:

Demolition July-Aug 2014:

The first step was to demolish an old brick garage at the back of the existing house. We did this piece by piece, removing the windows and doors and then slowly demolishing the brickwork and roof by hand, being careful everything fell safely onto our side of the boundary with the neighbours. The demolition was relatively straightforward, we kept some of the bricks for infilling patches of the existing house, and kept the concrete base for an old shed for tools and materials storage.

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Foundation dig Sept-October 2014:

IMG_3417With a little help from a neighbour with a mini-digger the foundations were dug quite quickly. Once dug, the Building Control Officer came to check on the ground conditions and asked us to go a little deeper and change the design of the foundation slightly to allow for the possibility of shallow mining in our area. This was a little frustrating, we had to work with the structural engineer and BCO to agree a revised design and dig some more, but at least we know the foundations shouldn’t go anywhere! This stage was very hard work, barrowing tonnes of damp, clay soil from the trenches to the front of the property, where a grabber would come regularly to take the spoil away, and felt very destructive, leaving the site in a worse condition from where we started, but at least the footprint of the new extension starts to become apparent.

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Drainage and concreting October – November 2014:

The drainage for our extension runs from the back of the house beneath the extension, so alongside digging foundations, we dug trenches for the new drainage. This was made slightly more difficult by our need to keep living in the house and keeping the old drainage running alongside the new for as long as possible, but we got the new drainage reconnected (after a few days without a working toilet!) and the BCO checked the system before we covered with pea gravel and prepared for the concrete pour over.

The concrete pour was very satisfying, with tonnes of concrete arriving on two very early Saturday mornings. We found a great company who were very understanding that it was a self-build project. They came to site twice before we started, once to check the access and the night before the first pour, while we were busy installing the reinforcement, to check that we were ready. On the day they worked around the fact that we couldn’t afford a pump to get the concrete to the back of the extension, and poured in stages, allowing us time to barrow, shovel, rake and wrestle the concrete around to the back of the extension before pouring more. One thing we have definitely learnt is that finding companies that understand that it is just you doing the work, and making sure that you and them completely understand how things will be done before they start is essential.

 

Winter hibernation November 2014 – February 2015:

With the concrete in and the weather turning, we took a break from building to plan the next stages. The main frame for the building was to be SIPs (Structural Insulated Panels), so we spoke to and visited a number of companies to find a supplier who again understood our position, and were willing to work with us on the design, delivery and advise on the build of the frame. Working alongside an existing building has definitely been one of the most challenging parts of the extension build. The existing 1920’s house has moved and settled over the years, aligning this with a SIPs system that works to very little tolerance was a challenge at both design and construction stages. To ensure we wouldn’t be left short, we agreed to oversize certain elements of the frame to allow these to be cut to size when on site and exact measurements at the correct heights could be established.

A bit of blocIMG_4152kwork February – March 2015:

When the weather improved slightly we got on with preparing the base for the SIPs panels. Being timber panels these have to sit above the finished ground level, so a base was built up in blockwork, clad in blue brick slips with a black mortar to the outside. This base construction can be a thermal bridge issue with SIPs construction, to mitigate this we used thermal, lightweight blocks (which are also easier to move around!), but these have also given us a few problems. To fix the baseplate for the timber to the blocks, we had to source special fixings to ensure a good fix into the base, and took several attempts before we found a method that didn’t also crack the block.

 

Panel construction April – June 2015:

The SIPs panels arrived as a big flat pack jigsaw puzzle, alongside a laminated set of instructions. Each wall was built from several panels, splines, timber posts and lintels. Every panel had to be found by it’s unique code, fitted with any splines and timber end pieces needed and lifted into place. It was a physically and mentally hard job, but the walls went up very easily and quickly, although we did slightly regret not getting a nail gun to save a lot of hammer time! Within 2 days, all the walls for the ground floor were in place, which was incredibly rewarding to see.

 

Joists and lifts June – July 2015:

_IGP9747When the ground floor walls were built, the next step was to install the first floor, before raising the walls on the first floor. Again the main difficulties with this was the connection back to the existing (wonky!) old house. We fixed a timber wall plate to the existing house, then laid joists between this and the top of the ground floor SIPs. Getting this level and working out how to fix all the elements together was a lengthy process and involved ordering several types of joist hanger and a bit of trial and error before getting it right! But with the floor in, the first floor SIPs walls went up as easily as the ground floor, and the flat roof construction was similar to the first floor, so quicker with experience.

 

All covered up July – August 2015:

With the main frame all in place and inspected by the BCO, it is now slowly being covered up. The outside of the panels are covered with a breather membrane, to allow the timber to breathe but avoid moisture penetrating the strcuture, and this is covered in timber battens, to allow ventilation, and thermowood cladding. The cladding is treated with 4 coats of black Sadolin stain. To save money we decided to treat the timber ourselves, again adding a lot of time, but thankfully both our parents volunteered for a few weekends to help us get the base coats on. Whilst we get on with cladding, roofers are working around the unseasonably wet weather to get the GRP roof coverings on. The low roof over the dining room will be planted, but we’ve decided to wait now until next spring before installing this, so we can take our time choosing a system that we are happy to install and get the right plants in place (we already have a few sedum plants growing in the garden that we hope to move onto the roof!).

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Windows and doors are also in manufacture and due for installation next week. This is one of the most expensive elements of the build, so again we have taken our time choosing a manufacturer and system that we were happy with. We also waited until the frame was up before placing any order, so that we could be sure that the planned sizes matched the as built window openings. More confident builders may be able to place the orders based on as designed sizes to save on the overall build time, but with our lack of building experience it was better to wait before ordering. The windows and doors are going to be double glazed and thermally broken aluminium frames, with solar control to the south and west facing windows. I can’t wait for them to be arrive and the extension to be watertight and ready for us to get on with the internal work over winter!

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Main advice for self-builders so far:

  • If you don’t understand something, ask for advice – whether from the architect, structural engineer, consultants, manufacturers or sub-contractors. If they’re not prepared to help, then you’ve not found the right one yet.
  • Give yourself plenty of time to find the right systems, right sub-contractors, make and correct first time mistakes, and enjoy the process!