Palestinians in Gaza have developed an industry that recycles twisted steel bars and smashed-up concrete from bombed structures as a way to rebuild the coastal enclave.

In a trapped society living under persistent attack, the reuse of materials has become a vital part of a construction sector flailing under the strain of an Israeli-Egyptian blockade that severely restricts imports.

Across the territory, among the dust and wreckage of buildings flattened in Israeli airstrikes, workers can be seen collecting chunks of walls and floors with diggers, and driving them off to be crushed. At one bombsite in Gaza City, Abu Mohammed sat drinking bitter coffee under a plastic tarpaulin attached to a shipping container that is his temporary office. A few metres away lay a slumped ruin that was built to be a public library but was later abandoned and used by Gaza’s rulers, Hamas, for public parades.

Since 2007 we've had a lot of work. It's busier during wartime Azzat Nassim, recycler

“If there is no war, we do nothing,” said Abu Mohammed, who asked to use his nickname as he did not want to be publicly identified. “When there is a destroyed building, we make contact with the owner to arrange salvage. This time it is with the government.”

One of the main products he extracts from the detritus is gravel – used to make concrete and to build roads. Sometimes, when residents cannot afford asphalt, gravel is laid down. “In some neighbourhoods of Gaza, most of the smaller roads are made of debris from bombed buildings,” he said.

Gaza, geographically cut off from the rest of the Palestinian territories, has suffered a decade-long blockade. Israel argues it is to prevent Hamas using materials for military purposes, such as building underground tunnels. For these reasons, construction materials are often heavily restricted or banned, including cement, steel reinforcement rods, pipes and gravel.

Even when the border crossings are open, imports are extremely costly and time-consuming to acquire, compounding an already disastrous situation for Gaza’s two million residents, vast numbers of whom are unable to leave. Unemployment is among the world’s highest, with every second worker out of a job. This summer, Israel blocked all commercial goods apart from what it deemed humanitarian supplies. The new restrictions came after several weeks of protests by Palestinians near the perimeter fence that were met with Israeli sniper fire.

More than 170 Palestinians, including children, medics and journalists, have been killed by the Israeli army. Several thousand more were shot in the legs. In response, Palestinians gradually began to fly kites carrying lit cans of petrol to spread fires in Israel. The violence eventually led to the most severe fighting since the conflict in 2014, with Israel using airstrikes, and Hamas mortar and rocket attacks. In July, an Israeli soldier died after he was hit by Palestinian gunfire.

It was during that period that the building being salvaged by Abu Mohammed’s men was hit. “This is the biggest project I’ve worked on so far, around 80,000 sq metres. It will take about 35 days in total and we’re 25 days in,” he said.

Recycled bomb-site gravel is cheaper, about £15 a tonne, he said, instead of imported gravel that can be £30 a tonne and even higher during border closures. It can be good business, Abu Mohammed said.

Occasionally, and especially when working on a bombed apartment building, his workers find personal items – clothes, toys, kitchenware – that survived the burial and return them to the owners, he said.

About a dozen of his men work to straighten twisted steel rods, using large cranks and wrenches covered in grease to leverage the metal. Azzat Nassim, 27, who has four children, wears a hat to shelter from the sun but said his 7am to 7pm day is tough. He gets about £40 a tonne, he said.

“We’re the experts,” he shouted out, not stopping work to talk. “The short bars that have been cut in the bombing are used for foundations.” The longer ones, which sit on a pile on the ground next to him, are used in high rises.

“Since 2007, we’ve had a lot of work,” he said. There have been three all-out wars between Israel and Hamas and myriad smaller conflicts in the past decade. “It’s busier at wartime.”

Recycling has become crucial in Gaza, where not only goods but also services such as water and electricity are often unavailable. As well as the blockade, economic restrictions imposed on Hamas by its Palestinian political rivals in the West Bank have all but destroyed the economy. Residents, mainly the descendants of refugees who fled or were expelled from what is now Israel, have relied on other blockade-coping strategies, such as solar power and batteries that charge during short periods when the power works. One eco-focused project, Green Cake, has used discarded coal and wood ash instead of cement, and bombed-building rubble as aggregate to make breeze blocks.

The thinking has seeped into the construction industry. On the outskirts of Gaza City, a small family-run factory mixes the bomb site gravel with cement and sand. Hundreds of breeze blocks dry in the sun.

Mahmoud Azzam, 49, used to drive gravel from Israel to Gaza and the West Bank but is now not allowed into Israel and so set up the factory. “These blocks are lower quality but cheaper,” he said. “We find bits of plastic pipe, small pieces of wood, bits of steel. When the border crossing closed, imported gravel runs out. But we continued.”