Stunning ICF Home with a Butterfly-Style Split Roof, Set in Beautifully Landscaped Gardens

Martin and Mandy Newnum have self built a beautiful new home accompanied by a stunning landscaped garden with water features that run right up to the building
Emily Batesmith

Backed by the experience of converting their large garage into a small one-bedroom home, Martin and Mandy Newman felt the time was right to take on the big house build they’d long dreamt of. “I’m 65 and thought, if I don’t do the project that’s in my mind now, I’ll never do it,” says Martin. A great view was the big-ticket item for the couple; however, they struggled to find the perfect plot. “There was an opportunity near the coast, but that vista also came with the wind,” says Martin. “We realised careful garden planning and landscaping could create the scene instead.”

When they visited the half-acre plot, they ended up buying, even though it didn’t come with that sought-after view, the overground garden surrounded by trees could be transformed into the right place for them – plus they loved the privacy it offered. It also came with planning permission for a five-bedroom house with tile-hung elevations. And although this wasn’t the house they ideally wanted to build, knowing there was consent to build was a winner, so they went ahead with putting an offer in, which was accepted.

This all happened before the Pandemic hit, but in April 2020, as the world turned upside-down, the sale of their home fell through, meaning they needed to pull out of buying the plot. And, to add to complications, they were in lockdown at their property in Greece at the time and unable to get back to the UK.

Their home had previously been the garage of the neighbouring property – a house that had originally been theirs before they’d converted the garage and split the land. It transpired that the owners of that house were interested in buying their one-bedroom garage conversion, helpfully putting the couple back in the position to buy the self build plot. “Our second offer on this land ended up being lower – we didn’t want to be rude, but everyone had lost invested funds in Covid,” says Martin. “We were even able to a deal with our neighbours to become their tenants and keep our old house while working up a design and going through planning.”

Developing the house’s unique design

They looked at replacing the existing planning permission with a house design better suited to them. “We didn’t have something particular in mind before finding the land, as we knew you can’t pick out a house style until you can establish how it sits in your building plot,” says Martin, who worked with a local architect to create new plans for a single-storey dwelling with a double monopitch roof.  “As we went on with the design process, we got involved in trying to make the property more sensitive to its surroundings. We saw the house as sinking down, with the garden growing up around it.”

Stunning ICF Home with a Butterfly-Style Split Roof, Set in Beautifully Landscaped Gardens

The overhang of the property’s roof is angled. Instead of using parallel steeled beams they used normal steel beams cut at an angle, which was a lot cheaper than having special ones made

The layout was inspired by a butterfly they’d seen land on their plot when it was still an overgrown garden. “It struck me that this could be the shape of the building, with the accommodation in one wing and the living spaces in the other,” says Martin.

The floorplan consists of two rectangle-shaped wings, connected by a glazed link entrance hallway. The space is all on one level and every detail was thoroughly considered. “Being in our 60s, we didn’t want any stairs,” says Martin. “We also wanted to be able to drive the car right up to the door and not get wet bringing the shopping in. We liked the idea of a living roof, of ponds either side of the hallway entrance and a bridge to the door, with rooms pointing in the right way for the sun.” The bedroom side of the building sits parallel to the edge of the plot and the other rectangle is angled to ensure daylight falls into the living spaces in the morning and early evenings.

Stunning ICF Home with a Butterfly-Style Split Roof, Set in Beautifully Landscaped Gardens

The entrance hall acts as a glazed link between the property’s two wings, with living spaces on one side and bedrooms on the other

The planning application was submitted during the Covid months, but the parish council objected to it at first as being too modern and not in-keeping with surrounding houses. “But the planners were keen, as were our neighbours – there was already permission for a big home and we were asking for a single-storey house,” says Martin. It went to committee. The couple had two letters of support and in the end, the vote won in their favour.

Fact file
  • NAMESMartin & Mandy Newnum
  • OCCUPATIONSRetired
  • LOCATIONWest Sussex
  • TYPE OF PROJECTSelf build
  • STYLEContemporary
  • CONSTRUCTION METHODICF
  • PROJECT ROUTECommissioned architect; homeowners project managed
  • PLOT SIZE0.5 acres
  • LAND COST£400,000
  • BOUGHT2020
  • HOUSE SIZE185m² (plus 125m² garage)
  • PROJECT COST£688,000
  • PROJECT COST PER m²£2,219
  • TOTAL COST£1,088,000
  • BUILDING WORK COMMENCEDJuly 2021
  • BUILDING WORK TOOK48 weeks (plus three years to final sign off)
  • CURRENT VALUE£1,300,000

Deciding to build using insulated concrete formwork (ICF)

Martin and Mandy got quotes for both timber frame and SIPs build methods but decided to go with insulated concrete formwork (ICF) as the structural system for their self build. However, they came up against an issue with their supplier as it transpired there weren’t enough ICF blocks to build the house.

“We took them to court, but as we hadn’t established it wasn’t right when the blocks were delivered, we were in the wrong,” says Martin. “You’d never be able to know that when your plot is full of polystyrene; however, it was in the company’s terms and conditions.” This caused stress and left the couple £3,000 out of pocket. “That was the only unpleasant part of the project,” says Martin.

Stunning ICF Home with a Butterfly-Style Split Roof, Set in Beautifully Landscaped Gardens

The mix of cladding looks striking, with vertical boards (also featuring under the overhanging roof) on each of the wings. Tiled cedar shingles on the central section works to give the appearance of two rectangles being pulled apart to expose a core

The couple had always planned to get hands on with their self build, taking on the project management. “It was sometimes difficult to know what to commission out – then every so often you spoke to someone who sounded like they saw our vision,” says Martin. “It was down to whether I thought they’d do a good job and if we’d get on.”

The groundworks caused a complication, as their structural engineer’s boreholes in the clayish sand ground exposed the need for 2m deep foundations – which came with an unexpected cost of £20,000. “Things had already begun to go wrong before we’d started to build,” says Martin. “But I was here all the time, and I was fascinated.”

CLOSER LOOK Ponds alongside the building

The entrance to the house acts as a glazed linking corridor between the two rectangular wings of the house. Martin and Mandy loved the idea of having a pond on both sides of this section. “Originally this was going to be two ponds connected by pipes, but it felt like there was too much potential for it to go wrong and leak under the house, so it’s two separate pools that butt up against the walls of the house,” says Martin.

Stunning ICF Home with a Butterfly-Style Split Roof, Set in Beautifully Landscaped Gardens

“We knew nothing about how to make these ponds happen and it took a huge amount of research, but they were a big deal to us in terms of the design.” The result is spectacular and the water can be viewed from numerous rooms in the house, including when walking over the entrance bridge to the front door.

Hiccups along the way

The Newnums moved out of their garage conversion and into a caravan on their self build plot just as the ICF blocks started to be laid in September. Although they were in the fortunate position to spend a month or two in their Greek house at this point, coming back to life in the caravan was a bit of a shock. “It was only three degrees inside the caravan one day – it was quite miserable and an added strain,” says Martin.

Stunning ICF Home with a Butterfly-Style Split Roof, Set in Beautifully Landscaped Gardens

The open-plan living-dining-kitchen is filled with wooden details and benefits from spectacular views of the surroundings

They were around when the first concrete pour into the ICF blocks took place. “We made a big effort to put plastic pipes through the polystyrene to run electrics through where we needed it, as you end up with a six inch steel-reinforced concrete wall, which is a nightmare to cut,” says Martin. “And we know this to be true, as we ended up having to cut through it to put another window in.”

This came to light when it transpired they needed a fire escape in the snug, as it’s positioned off the kitchen and there were no opening windows. “There was one planned, but the architect left it off the glazing schedule at the last minute – plus the exit was over the pond, which Building Regulations wouldn’t have allowed either,” says Martin. “This was the only thing that went wrong with the design.”

Stunning ICF Home with a Butterfly-Style Split Roof, Set in Beautifully Landscaped Gardens

The level threshold between the open-plan hub and patio creates a wonderful inside-outside living space

As they started getting into November, with shorter days, they felt pressure to keep things moving. “Mandy was up on the roof under the flood lights putting in thousands of screws,” says Martin. The flat topping is covered with a living green roof, which caused several headaches. “There was a leak in the roof and the membrane must have been slashed accidentally, which meant we needed to redo the plasterboard in the entrance hall,” says Martin. “Also, the gutters along the edge of the roof have downpipes into our ponds, but it turns out that the nutrients of the living roof can’t be in the pond – we didn’t realise that so it has to empty somewhere else.”

Creating the perfect result

For car enthusiast Martin, building a good-sized garage was another important part of the project. “You can’t generally get a garage this size unless you build it,” says Martin. “There was a bit of an issue with planning as they didn’t want it bigger than either of the rectangular blocks in our house, so it’s ended up being a bit smaller.”

Stunning ICF Home with a Butterfly-Style Split Roof, Set in Beautifully Landscaped Gardens

Rooflights over the kitchen space flood the home with natural light

The finished combination of the main building, the garage and the beautifully landscaped garden creates a striking home full of eyecatching details and clever design. The building features a mix of timber cladding (both outside and inside), angled roofs with overhanging edges, corner glazing and two ponds that surround the building a bit like a moat. The garden offers peaceful natural surroundings thanks to an attractive mix of planting that certainly creates the views that the couple were after. “We thought the garden would be about 25% in terms of importance in the project, but as time has gone on it’s become more like 50%,” says Martin.

Stunning ICF Home with a Butterfly-Style Split Roof, Set in Beautifully Landscaped Gardens

Glazed sliding doors pull away from the corner space, maximising garden views and the indoor-outdoor connection

The airtight house is heated by an air source heat pump and underfloor heating (UFH), with the interiors remaining fresh thanks to a mechanical ventilation with heat recovery (MVHR) system. “I put all the piping in for the UFH myself really neatly – but then you have concrete poured on it so never see it! But I know it’s there,” says Martin. The rooms are filled with natural light with a mix of colourful walls, white bright spaces and natural wood finishes. There is smart home technology automating the lights, security cameras and entrance gate – all controlled via Apple Home Kit.

The kitchen-living-dining area is the couple’s favourite space. “It’s quite large and airy with a high roof, plus the big windows mean we can see out. It’s like living outside, just like we’d done in Greece,” says Martin. “The decking runs out at the same level as this space and we love that you can hear the running water – it’s so calming.”


We learned

  • When your floors aren’t in yet it’s very difficult to work out levels for getting ceiling heights right. Builders use spinning lasers on the walls, marking a line 1m above where the floor will go in, then working out everything else from that. Our front door is just a few mm short of the top of the ceiling – in fact, the door wouldn’t go in at first and we had to put in thinner plasterboard to allow it to swing open.
  • We couldn’t find a kitchen that we liked, we saw an amazing cabinet maker on a local art trail and ended up having him make the kitchen doors and veneered edging on the island. It was a big luxury, but worth it, as we knew we’d touch and look at it everyday.
  • The bifold garage doors open out, which was quite an involved thing, but they are brilliant as you can open sections at a time. Having a slight overhang on the garage roof is great, too.

Emily Batesmith

Emily Batesmith is Build It's Contributing Editor, and an architecture addict. She has an in-depth understanding of the challenges self-builders and renovators face, as well as a keen eye for design. Alongside writing regular features for Build It, she curates all of our real-life reader homes.
Read more articles by Emily Batesmith

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