What it means
A shedload is a massive amount of something, the sort of pile that feels like it could fill a garden shed. Nobody’s measuring it with a tape, it’s just a handy, slightly daft way to say loads, usually with a bit of mild disbelief. Works for work, food, emails, grief, you name it.
Usage examples
"I said bring snacks, not a shedload of sausage rolls. Now Dave’s turned up with a shedload of mates and the kettle’s already on its last legs"
"We sold a shedload of tickets in the first hour alone."
"There is still a shedload of work to get through before Friday."
"I’ve got a shedload of washing to do and absolutely no intention of starting it tonight."
"They brought a shedload of cans for a quiet one and turned the flat into a full-blown circus."
Where it comes from
Shedload is British English from the late 20th century, built as a softer, non-swearing swap for shitload. It keeps the same big-quantity punch but makes it safer for everyday chat, with shed adding that nicely cluttered mental picture of something piled up far past sensible.