Fifteen-year-old Jack Morris was born with a rare form of muscular dystrophy, which has led to a lifetime of painful operations. His mother Helen has always been his rock and his elder brother Daniel his best friend. But as Jack grows into a man, it has been impossible for Helen to get him upstairs and he is forced to sleep in the living room of their small three-bedroom semi in Swansea. With no other social space in the house, Daniel rarely brings his mates round and they spend less time together as a family. So Nick and the boys, with designer Gabrielle Blackman, take on the challenge of turning the house into somewhere for Jack to grow into a man with dignity, a place to give Helen sanctuary and to reunite two amazing brothers.

Scott Russell and Jenny Watts got together when they were 16-years-old. Twenty-two years and three boys later, they are now a family of five. Charlie, their third son, was born with severe disabilities - spastic quadriplegic cerebral palsy and global developmental delay. He needs around-the-clock care, which Jenny has given up work to provide. Since he was born 13 years ago, they have struggled in a two-up, two-down end-of-terrace home, and Charlie faces going into care because they simply cannot keep him at home. Carrying him upstairs is a daily battle, and the older boys, Danny and Bradley, are crammed into tiny converted attic rooms. In the biggest build ever on an individual house, Nick, the boys and Naomi Cleaver rebuild the whole of the downstairs as well as remodelling the rest of the house to provide a more suitable home to bring Charlie up in and keep him at home with his family.

In April 2012, 35-year-old Mark Burrows had retrained to follow in his father's footsteps as a scaffolder. Then, during an unprovoked attack, he fell and hit his head on the pavement, resulting in severe brain damage and paralysis. Now unable to walk, talk or feed himself, he requires 24-hour care, something his parents Frank and Christine are desperate to give him, rather than him being in a care home 15 miles away. With the help of flamboyant designer Laurence Llewelyn-Bowen, Nick and the boys take on the task of building a self-contained apartment alongside Frank and Christine's two-bedroom bungalow so that after two years away, Mark can at last come home.

Nick Knowles comes to the aid of Liz and Jason Liversidge, a Hull couple in desperate need of help in future-proofing their family home. Not long after getting married and starting a family, Jason was diagnosed with both Fabrys disease, which causes a build-up of poisonous toxins in the body, and Motor Neurone Disease, which drastically reduced his life expectancy. The pair also discovered that Jason would have passed Fabrys disease on to his two daughters, which means that once her husband is gone, Liz will need all the help she can get in managing her children's condition. Nick joins forces with designer Oliver Heath and an army of volunteers to put together a home in which Jason can build meaningful memories with his girls, but one which also gives Liz the best chance of providing for their future needs.

Identical twins Katie and Emelia were born with achondroplasia, a form of dwarfism. At just 41, dad Mark is recovering from aggressive bowel and liver cancer. The family are struggling for space and in desperate need of some good luck. Thankfully, the DIY SOS team are on hand to help build them a home for a better future.

Paramedics Sam and Ben Laws spend their days helping people. With two children to look after, one with special needs, they work opposite shifts, often not seeing each other for days on end. While they have done everything they can as a family to make life better, the challenges of living in a totally inadequate home have been overwhelming. Reluctant to ask for help, they had to be nominated by a close friend for Nick, the boys and designer Oliver Heath to transform their house from the prison it has become into a stunning home that could offer five-year-old Ewan the best hope for the future.

Nick Knowles and the DIY SOS team are back for a two-part special with their most ambitious build ever, and this time they are joined by two special royal helpers. The team are taking on a whole street in Manchester and turning run-down empty properties into homes for veterans. The team rally the local community to get stuck in and are also helped by Prince William and Prince Harry, who volunteer on site. In this show, the trades come together to build homes for two former soldiers who fought in Iraq and Afghanistan and are suffering from post traumatic stress disorder (PTSD), before also helping them to find new careers in the building trade. But with numbers of volunteers lower than what's needed and the buildings proving trickier than anticipated, it's turning into the toughest build yet.

In the second episode of a two-part special, Nick Knowles and the DIY SOS team continue with their most ambitious build ever - an attempt to regenerate a rundown community in Manchester. The team are aiming to transform an entire street, turning empty properties into homes for war veterans and building a support centre to help other veterans find homes and jobs. The plan is to redo the fronts of all the houses and put in new utilities - but with late nights and delays, it is looking like the team might not meet their deadlines.

The team transform a family's house in order to assist Richard's recovery, after suffering a brain stem stroke, and build a new family home. Ten years ago Richard and Jude Ford met while working for the police. They married and started a family and now have three sons, nine-year-old Harry, seven-year-old Oscar and Archie who is four. Richard was a keen athlete and coached his sons' football club, but in June 2012, two weeks after running the Edinburgh Marathon, he suffered a devastating brain stem stroke and he was put into an induced coma. For 9 months he suffered from locked-in syndrome, meaning he was aware of everything that was going on around him but could not move or communicate. He's no longer locked in but Richard has limited movement and speech and is confined to an electric wheelchair, communicating via an iPad. Since his return home, the family have had to convert the children's playroom into a bedroom for Richard. He has no choice but to use a commode chair to go to the toilet, sometimes in full sight of his family. Tragically, though his body no longer works, Richard's mind is unaffected, so he is fully aware of his situation. He has very little privacy or independence. With the aid of his iPad voice simulator he tells us 'all I want is to be a husband and a father again'. Reluctant to ask for help, Nick, his team and designer Charlie Luxton transform the Ford's house in order to assist Richard's recovery and build a new family home.