From the outside, this single storey rear extension appears to be the run of the mill permitted development, adding a little extra kitchen depth, and enlarging an adjacent dining room, with the existing floor plan remaining relatively untouched. But behind those French doors, the entire rear wall of the existing property has been removed, creating a large open plan area, and totally transforming the entire look and feel of the ground floor in the process.
This article will walk you through the construction process of a home extension, from beginning to end. Showing images at various stages of the project in chronological order, and explaining some aspects of the build in more detail.
If you are about to have major building work carried out on your home for the very first time, this could be an invaluable resource, to give you an understanding of what to expect during the build, to hopefully leave you better prepared for any impact this may have on day to day life in your home.
This is the rear garden, a few weeks before construction is due to begin.
Existing radius wall, that looks nice. Somebody should write a blog article about that.
The excavation can often be a frustrating part of the job, if the ground conditions are wet and boggy, through winter especially, but it's all part of the job, and no job is without it's hard tasks. Fortunately ours was a pretty straightforward job, with dry and warm conditions, which made life just that little bit easier for us during the dig out. It also makes the excavation quicker, done in around two and a half days, which might not sound quick, until you consider there was 45 tons taken away by a grab hire.
We used a one and a half ton mini digger, and a one ton dumper, which could both fit through the side entry of the property. All the excavated soil and waste was loaded into the dumper, and piled on the driveway, which was heavily protected by a extremely thick polythene layer on the drive to stop anything leaking onto it, covered by thick marine ply. The waste was taken away by grab hire.
We spoke to the building control officer allocated to us by the local authority, regarding our proximity to a tree on the neighbouring property, and after a discussion with him during his first site inspection, we agreed on a stepped footing, with claymaster heave protection at the end closest to the tree.
You can see the problem tree in the top of this image, rising above the fence in the neighbours garden. The stepped footing begins that end, at its deepest depth of 2.5 metres, with the previously mentioned claymaster in the side of the footing, helping to protect against the shrinking of the soil caused by the tree sucking the moisture out of the clay. The depth continues at 2.5 metres around the first corner, then stepping up slightly at 1.5m intervals, reaching the reduced depth of 1.5 metres at the other end.
Once the dig was completed, we dug the footings for the surrounding retaining walls, to a depth of 1 metre, and had concrete delivered, and poured in using a pump delivery system. the concrete is trench poured, in this case meaning the concrete finishes roughly 450mm, or 2 courses of concrete footing blocks, below ground level.
Once a few days curing time has passed, the concrete footing blocks, and the blue brick damp course are laid for the extension and the retaining walls. Type-1 hardcore was then compacted inside the extension, for the floor slab base, and also in the garden where the patio will eventually be built.
A layer of sand protects this black damp proof membrane from being punctured by the compacted stone beneath it. We then put into place the 100mm Celotex floor insulation, with 25mm insulation around the edge, and another thinner layer of DPM over the top, as per building regulations requirements.
Once the building inspector visited site to approve our work, a 100mm concrete floor slab was poured in and trowel finished.
Its at this stage in the project, when all that sticky, boggy clay, that clogs up your boots, is either dug out and taken away, or covered over with aggregate, where the bricklayer, in this case me, can really begin to get their teeth stuck into things.
The next phase of development is where we begin to see things taking shape above ground, but I hope this segment has given you a better understanding of the amount of planning, time and knowledge required to complete the work below.
Timber door profiles were manufactured on site, and we began to build brickwork around them. Using profiles in this way, ensures not only a neat and plumb finish, but allows for accurate enough sizing of the openings to allow doors and windows to be ordered before the shell is completed, and thus minimise any possible waiting time for delivery.
The facing bricks used are an exact match to the existing property. All brickwork is also toothed in where the extension adjoins the existing house.
Once the masonry shell was completed, we cut and assembled the timber roof structure, and finished the verge cut brickwork at both ends. This is also the point of our next inspection, Where the building inspector checked our cavity wall brickwork, and monopitch roof comply with building regulations, and match the design shown in the plans.
This is a good stage in the roof tiling to show an image of, as it shows the breathable felt and roof batons beneath the tiles, and also shows how the skylight flashing sits above and below the tile. Upon completion of the roof, along with lead flashing, the 2 sets of french doors were fitted, which allowed us to then begin the internal work.
Weighing in at over a ton for this section alone, it was a slow and carefully managed procedure to move the beams to the rear garden on these heavy duty trolleys. The process of getting this beam inside and in place, when its almost as wide as the house itself, was planned weeks in advance, to be absolutely certain it was possible.
After carefully removing and disposing of the wall, adding more props as we worked left to right, we manoeuvred the main beam onto 3 genie hoists (pictured on the left). once tightly jacked up and propped, we could concentrate on the 2 steel stanchions.
One last check of measurements were taken either end, making certain of correct position and angle. The 2 stanchions fit plate to plate on the ends pictured above. Everything had to be millimetre perfect, otherwise the stanchions would be out of plumb, or worse still, they simply would not fit.
Point loading is a term you will hear a structural engineer mention, when he/she is calculating for a wall removal. Basically, the less wall there is touching the foundations, spreading the weight of what is above, the more of that weight is loaded onto the points that still are. Here we see a method of countering that, by widening the existing footing where the stanchion loads the weight. After connecting bars were drilled in, we poured concrete up to steel level.
Both stanchions were bolted to the main beam, and also bolted to their new concrete bases. when the support props were removed a day or 2 later, work began to construct the timber frame to which the fire proof boarding will be attached. framework was also built to hide the water and soil pipes from the upstairs bathroom. The building inspector assessed and approved the steel installation, and allowed us to proceed. As the main contractor, part of our service is to deal with building control on our clients behalf.
Building regulations insist on all new steelwork being boxed in with fire rated plasterboard, which in the event of fire, gives vital extra time before fire and heat begin to weaken the beams. The boards are then plastered in just the same way as standard plasterboard. We are now ready to pour latex floor leveller, complete all first fix electrics and plumbing, ceiling insulation, and continue the dry lining.
Once the remaining first fix electric and plumbing works were completed, we dry lined with plasterboard, and our team of fully qualified plasterers gave everything a professional plaster skim finish. As with all our projects, every wall or ceiling we plaster, is done so to the highest standard, and is ready to be painted.
For this project, our client, with close assistance and advice from us, and through one of our partner suppliers, chose to purchase the kitchen themselves, and use us on a labour only basis for fitting. When carrying out a build such as this however, all kitchen plans need to be finalised, and presented to us before first fix electric and plumbing work commences. Our project managed service makes this process as painless and smooth as possible, by coordinating all of the relevant design, supply and construction trades through the various phases of installation.
After the kitchen is installed, we can complete all second fix electrics and plumbing. For this project, it signals the final stage of the internal works. After a good clean up, presenting of certification from our plumber and electrician, and the nod from building control, We can now begin the final stages of the external work.
Here we can see work taking shape over those foundations we poured alongside the extension foundations, way back at the start of the build. We are using the same facing brick as on the main property, to give everything that tied in, seamless look.
As part of our complete garden renovation package on this project, once the garden retaining wall was built up to height, we then imported more soil, to change what was originally a sloped lawn, into a level and even, freshly turfed one. It should be noted that land drainage was also installed behind the new wall, to prevent water retention, which can lead to a damp and boggy garden during the rainy seasons.
We never cut corners, and we firmly believe that whats below ground is just as important as what you see above it. This is where we struggle to compete on price with some other builders, as we never compromise the prep work necessary for a long lasting product. Here we see the final base layer of stone for the patio paving, which has been compacted using a vibrating whacker plate, pictured left.
The transformation is complete! Raised beds, a solid retaining wall that will never move an inch, gently rising, evenly spaced garden steps leading to a brand new lawn, and a new patio. Designed and constructed with every attention to detail. If you scroll back to the top of this page, and look at the before construction image, you will barely believe that you are looking at the same garden.
And there we have it, a unique, detailed, chronologically ordered insight into the building of a home extension. It may feel after reading this article, that you were right there with us the whole way through the build. During which, at times you've been informed, at times you've been intrigued, and I am sure, at times you've been bored stiff!
However you have taken it, it has indeed been a pleasure to have re lived this project with you.