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When Peter and Rhea Marshall of Co Antrim bought their house they did so with a view to building an extension, as their family was expanding. Nurturing the design process was their first priority… 

Converting a 1950s semi-detached house into an open plan, modern living space is no small feat but Peter and Rhea were clear about what they wanted, and about their limitations too so they got the ball rolling by looking for an architectural consultant.  

“We were complete novices,” confides Peter. “All of the rooms were quite small and the kitchen was disconnected from the rest of the house. I also needed an office.” 

“It wasn’t clear to us how to reorganise the space, we just knew it wasn’t working for us. We had an idea of the functionalities but weren’t sure about the layout.” Adding a new bathroom was also high on the wish list, as was introducing a light-filled living area, probably in the form of an extension.  

“We didn’t know how to extend or even in which direction,” he adds. “We did put together some initial sketches to see how much space we might gain, and took these to several architectural practices.” 

They approached different designers on the basis of recommendations and asked them about the process and the costs involved.  

“In the grand scheme of things and from an artistic point of view it was important for us to improve the aesthetics. This was originally a square of a house and we wanted a brighter and a more organic space,” adds Peter. 

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“We gave our architect our budget and he came back with sketches. To counterbalance the angular, box-like shape of the house, he introduced a lot of curves in key places and a long glazed opening extending into the garden.” 

“The addition of a deck draws the eyes outside, and that’s a feature I really enjoy now.” 


Three-year gestation period 

The design process took much longer than the Marshalls expected. “We went through two or three iterations of the design, for instance the new utility room originally didn’t have a window and we insisted on getting natural light in there, we also decided to add a shower to the downstairs wc,” explains Peter.  

“At this stage we felt like we had plenty of time, we were happy to spend it getting it right. We already really liked the house and the area we were in and since we knew we wanted to spend the rest of our days here we decided to invest in the design phase.”  

In total, the couple spent three years planning it all. “By the end of it we were getting quite impatient to get started,” remembers Peter. The build started in December 2012 and took six months to complete. “We were much longer designing it than building it.”  

An element that took a while to get right was the mechanical and electrical (M&E) engineering.  “When we looked at how to heat the extension, we decided to use the existing boiler as it had enough capacity. But the question was how to heat a large open plan area with a glass wall.” 

The engineer advised Peter and Rhea that using radiators alone wouldn’t reduce the cold spots caused by the glazing and wouldn’t heat the space evenly. 

“Since we wanted to create a comfortable space to live in year-round, we looked at complementing the radiators with either underfloor heating or trench heaters recessed in the floor in front of the windows,” says Peter. 

“We wanted the space to heat up quickly in the mornings so we went with fan assisted trench heating, which has the fastest response time.”  

“We also took time figuring out how to light the extension and where to put the sockets – the M&E engineer was kept busy!” Despite these efforts, some elements couldn’t be foreseen. “There were a few snags, for example the LED light fittings were buzzing so we got those fixed.”  

Not having done anything like this before they were keen to follow a predictable process, especially considering some aspects of the design were quite ambitious. “We were outside our comfort zone, and we were aware various things could go wrong,” adds Peter.  


“At this stage we decided to keep our architect on board to get us through the build; he’d already secured planning permission and sorted out the tenders for us. He covered all aspects,” adds Peter. The long planning stage allowed them to give builders very detailed tender drawings, which made selecting the right one easier. 

While the couple managed to live in the house during the works, there were some drawbacks. “We had to clean the dust off the countertops before we started to prepare food – it’s quite an invasive operation building an extension! – but we knew it was short term so it worked out.” 



“It’s a once in a lifetime experience, so we went high end on the finishes where we could,” says Peter.  

“For instance, when we got to the fixtures and fittings, we decided to fit a wooden floor – it’s hard  wearing but warmer than tiles or concrete. We also chose aluminium frames for the windows because we like how it looks, and for the low maintenance aspect. These elements added to the cost.” 

The windows are in fact the main feature of the extension, drawing the eye out to the garden. However Peter says that due to the big ‘picture window’ effect they were after, they had to go with a sliding system.   

“Not that many options were available to us; due to the size, span and height of the windows we were told we should go for sliding doors instead of folding ones,” explains Peter.  

“For people considering this option I’d recommend they look at the product installed in a few houses, to determine how effective the sliding system is,” he advises.  


“Our windows were done in three sections, which meant each section was at its maximum size and I now realise that the overall weight makes them not glide as well as they should. We’ve also noticed that the windows can be a bit draughty.”  

As the back of the house is south facing there is a risk of overheating in the summer but this was factored into the design.  

“The curve maximises the amount of light hitting the room in the morning,” says Peter. “The overhang limits the impact of the sun in the latter part of the day preventing overheating from happening in the summer. We also did some future-proofing so that we can install mechanical ventilation at a later stage if we feel the need for it, but haven’t yet.” 

Neither Peter nor Rhea plan to do anything on this scale again but theirs is a growing family with growing needs. Even though they love where they live, you never know, a self-build might even be on the cards… ν 

Astrid Madsen 

House size:  157 sqm/ 1690 sqft 

Plot size:  367 sqm/ 3950 sqft [/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text css=”.vc_custom_1470304206761{padding-top: 5px !important;padding-right: 5px !important;padding-bottom: 5px !important;padding-left: 5px !important;background-color: #f2f2f2 !important;}”]Build spec 

Floor: 85mm screed on 150mm PIR insulation board on damp proof membrane on 100mm concrete floor slab. Floor finish to living and dining areas: engineered timber floor boards. 

Floor finish to kitchen, utility room and shower room: large format ceramic floor tiles. 

U-value: 0.12 W/sqmK 

White curved wall: Cavity wall comprising 100mm dense concrete block inner and outer leaves and 100mm wide cavity filled with 100mm flexible full-fill cavity insulation. External finish: 18mm proprietary textured external render finish. Internal finish: 15mm plaster. 

U-value: 0.30 W/sqmK 

Brick faced wall: Cavity wall comprising 100mm clay brick outer leaf, 100mm dense concrete block inner leaf and 100mm cavity partially filled with 60mm PIR insulation board. Internal finish: Plaster. U-value: 0.24 W/sqmK 

Roof: Reinforced polymeric roof membrane on polyester fleece on 100mm PIR insulation board on vapour membrane on 18mm thick plywood sheet on tapered timber firrings on timber joists. Underside of ceiling joists dry-lined with 12.5mm plasterboard and skimmed with 2mm gypsum plaster. U-value: 0.22 W/sqmK 

Doors and circular roof light: Double glazed, argon filled, low e inner pane, polyester powder coated aluminium frames. Glazing centre-pane U-value 1.10 W/sqmK [/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

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