We built a £13,500 garden office. It saves £500 in monthly mortgage costs

Cheryl Crossley, 37, jokingly refers to her 4.5m by 1.5m garden office as a ‘coffice’: “It’s very narrow and a bit like a coffin but it’s perfect,” she says. It’s also saved her a huge amount in moving and mortgage costs, didn’t require planning permission, took three weeks to build and cost only £13,500. Cheryl is the head of PR at a digital marketing agency and lives with her husband and their 17-month-old son in a suburb of Leeds. Shorts They bought their three-bedroom, three-storey, semi-detached house in 2017 for £250,000 and for just the two of them, it was ideal. “We have a private garden but also access to a big communal garden, where the neighbours all get together,” says Cheryl. The exterior of the ‘coffice’ “We liked having the spare room for visitors and also an office where we can both work from home, but we also needed a bedroom for our son.” Their parents regularly come to stay, so having a dedicated guest bedroom was non-negotiable. When the couple found out they were expecting their first child, they started looking for four-bedroom properties in the same area, and discovered they’d need to increase their mortgage by £100,000, or even £150,000 in some cases, to ascend the next rung on the property ladder. “We had our house valued at around £335,000 and explored the cost to move, around £20,000 [including stamp duty], as well as the cost of a property with the extra space we needed, which was closer to £450,000,” she says. To fund this would mean the family paying an extra £500-a-month in mortgage repayments, right at the time when they would also start paying £1,000 a month in nursery fees. “That’s a significant amount of money,” says Cheryl. “I was feeling anxious about what that extra investment was going to look like and how we would afford it. I was also planning on taking a salary reduction when I went back to work as I wanted to be part-time. “Moving stopped feeling realistic.” Instead, the family started investigating whether they could use the narrow space between their house and garage. “We had previously explored extending into it from the kitchen and making a utility room, but a friend had a garden annex, and we decided to go and have a look at it,” says Cheryl. The interior of the coffice “We got quotes for garden rooms as an alternative to moving, and even at the top end – £25,000 – it still made more financial sense to go down this route,” she added. After deciding that this was the way forward, things progressed quickly. They didn’t need to get planning permission because of the temporary nature of the structure. “It doesn’t have full foundations, but groundworks and big screws that hold a load of cement. It’s then built on top,” she said. “It’s also not attached to the house.” The build took three weeks and was completed in December 2025. It cost £13,500 for the main structure, with an extra £1,000 spent on furniture and interior décor. She said: “Any build is difficult and stressful, but this was quick and it makes a massive difference. I can close the door on work and leave the laptop open without worrying that my son will get to it. “In there, we have a desk and a chair. It’s only small but you could put in a treadmill as well. Even if we both end up going back to the office five days a week, it’s nice to have the extra adult space”. Cheryl’s experience reflects a wider trend among UK homeowners. New research from Electric Radiators Direct found that 21 per cent of Brits feel their home is too small, while 61 per cent homeowners would consider building a garden room rather than moving home to gain more space. One unexpected benefit of this garden room is how it’s reduced the family’s bills. “We’ve saved £20 a month on gas and electric as I don’t need to heat the whole house, just this one room,” says Cheryl. What’s less certain is whether it has increased the value of their home. Two estate agents said the family would probably break even, while another thought it would add value to the right buyer. “A well-built and insulated garden room can typically add between 5 per cent and 15 per cent to a property’s overall value,” says buying agent Robin Edwards of Curetons. “Buyers increasingly see garden rooms as a genuine extension of the home.” In Cheryl’s case, the 15 per cent figure works out at roughly £50,000. But for this couple, the major plus has been that they haven’t had to increase their mortgage or splurge out on moving. “We will look to move again when our son starts school,” Cheryl says. “But it’s bought us at least another four years in this house. That gives us time to save up and be clear about what we want next.”