SATURDAY 29 NOVEMBER

In Cape Town airport, Niall Mellon greets the building blitz volunteers as they come off the plane. He has shaken 2,000 hands over the last couple of days.

We drive into the city past Khayelitsha, the township where we will be working for the week. It goes on for miles. People don't talk much; we are all – even the veterans – in shock. It was this same journey, taken seven years ago by Niall Mellon, arriving on holiday, and his conviction that no human being should live in a shack that was the genesis of the establishment of the trust. By the end of 2008, Niall Mellon Township Trust (NMTT) will have completed 10,000 houses, each one with a trademark red roof. This week, our target is to build 250 houses, giving 3,000 people a homé. I am travelling with my daughter Esme (15), a transition-year student.

In our hotel room is a kit bag with a week's supply of blue team T-shirts, the name of our team written across the back. We are Denim. I am relieved not to be a lemon.

SUNDAY 30 NOVEMBER

We are picked up from our hotels at 7am and bussed to an assembly point from where all 2,000 of us walk into Khayelitsha in our teams to start work, led by Mellon and Whitey Jacobs, a local housing minister.

We are the largest movement ever of white people into an African township. It is an emotional experience. Even this early in the morning, the streets are heaving. There are shacks that function as hair salons, cash stores, dentists, doctors, chemists, mobile phone shops and chair repair services. Gabriel's Undertakers offers funeral cover for 14- to 65-year-olds at a cost of 65 to 85 rand a month. Fly posters for quick and cheap abortions are everywhere. The shebeens will do a brisk trade today – Johan, an Afrikaans in charge of security for NMTT with 23 years in the Cape Town police force behind him – says Sunday is the most volatile day of the week. Many of the locals are dressed in their Sunday best. The sight of the shacks up close is sobering.

The Pink Lady supervising the bus back to the hotels announces that somebody has been given a red card by Mellon and sent home. Red cards are given for missing work due to alcohol or drug consumption.

"There are press all over the place," she says, "just waiting to write a bad story." By the end of the week, another two red cards will have been doled out, along with a dozen or more yellow cards for missing the morning bus after a late night. Behaviour is monitored closely. The reputation of the NMTT as a lean, efficient machine is held dear. But that doesn't stop the odd volunteer partying in Maverick's lap-dancing club until 5am.

MONDAY 1 DECEMBER

After a couple of hours lifting blocks and carrying planks from one end of the Denim site to the other, we visit Encotsheni primary school. On the bus radio, the morning phone-in show is sponsored by Contempo
Condoms – for maximum performance. The kids are cute, well-turned-out in their navy and gingham. All the volunteers want their photo taken with them. The children find Esme's train-track braces hysterical. They keep asking her to smile. Statistically, at least 20% of these children have HIV. They are, we learn, the ones with the runny noses. Everywhere we go in Khayelitsha, children sniffle.

We meet some of the families who will be getting the keys to their new houses at the end of the week. It's hard-going – the shacks range from squalid to spick and span but none could hold a candle to the average Dublin garden shed in terms of either size or comfort. I feel like an idiot for asking one man, who earns €10 a week as a gardener and has a family of six to support, what he's going to do about furnishing the new place. He says that he can't even dream of ever having furniture. Agnes Frans will also be getting a house at the end of the week. She lives with three of her children and her grandson, whose mother, Agnes' daughter, has abandoned him – "to go off and have a good time". She has taken the child benefit with her. Agnes sells crisps and fried fish at the school gates to earn money.

We pass TV presenter Glenda Gilson (painting team, light pink T-shirt) sitting on a block eating her lunch. Over at the garden, Diarmuid Gavin is wrecked. "I was here last year, and now I can't stay away," he says.

TUESDAY 2 DECEMBER, 2008

Over on the Yellow site, a middle-class neighbourhood by Khayelitsha standards, the team house displays a 'Vote Eoghan X Factor' poster in its front window. Mai Frisby from Sandymount is up a ladder painting facia boards in a facemask and a pair of rubber gloves. "We're the Swat team," she says, indicating her friend Caroline Desmond from Killiney, Mai's son Charles (at 14, the baby of the blitz), Caroline's son Jett and his friend Killian McNeive, both 16.

"I actually know now how to build a house from top to bottom," says a proud Jett Desmond. "I'd no idea how much it would mean to the people who are getting houses. It's awesome." For once the word is appropriate.

Caroline Desmond spent some of her childhood in Durban, and remembers those days. "Our nanny had to have a special pass just to be able to come on the bus with us," she says. Mellon persuaded her to come by telling her she'd do some good and lose 7lbs into the bargain. She says the exfoliant effect of the sand blowing around is better than any fancy Dublin facial.

WEDNESDAY 3 DECEMBER

Esme heads off to the site on the bus and I stay in the hotel to start writing. On the way to HQ at lunchtime, the driver, an Afrikaner, says: "You Irish must have hearts as big as mountains."

The country director from the World Bank, Ruth Kagia, comes to HQ for a meeting with Niall and the chiefs of staff for seven US congressmen, here on a fact-finding mission. I'm allowed to sit in.

"I'm with anyone who makes a dent in poverty, who closes the gap between rich and poor," she says. "Where there is inequality it is not possible for there to be stable society."

Eighteen months ago, Mellon gambled that Obama would win the election and has spent the time since courting the African-Americans in the US Congress. He has met with the majority of them since.

Michael Collins (yes, really), a tall, handsome African-American from Boston who is chief of staff for congressman John Lewis from Georgia, is at the forefront of a move to get key legislation through the new US Congress. "We want," he tells me, "to support Niall in leveraging dollars from US aid. Our target is 2010. We like his passion and his drive."

Esme comes back from site and is asleep by 7.30pm.

THURSDAY 4 DECEMBER

Work gets off to a slow start. The team is focused, determined to meet its target – handover day is tomorrow.

FRIDAY 5 DECEMBER

The houses are given to their owners. For many of the children, tonight will be their first night ever in a proper house. Many of us spend the day on the verge of tears. It is hard to leave when you see how much more there is to be done.

2008 Housing Blitz: Building Blocks

Where: Site C in Khayelitsha, the largest township in Cape Town

Population: 60,000

Area of Khayelitsha: same as Phoenix Park, site C is 300 acres

Target houses to be built in the week: 250

Cost per house: €7,000-€8,000

SA govt subsidy per house: €5,000

Number of Irish volunteers: 2,008, of whom 44% have a trade

Number of veterans: 721

Number on their sixth blitz: 24

Amount raised by each volunteer: €5,000

Ratio of men to women: 4:1

Number of colour-coded T-shirts provided to volunteers: 13,000

Number of bottles of NMTT builders' spring water consumed: 250,000

Number of people waiting for houses in South Africa: 10 million

NMTT local staff: 80 management, 1,900 construction

Local volunteers in 2008: 1,200 (70% white, most had never set foot in a township before)