This year's Open House weekend takes place on 21-22 September. 830 buildings across London will open their doors to anyone who turns up. Explore churches, office blocks, private homes, roof terraces, stately homes, skyscrapers, landmarks and any other type of building you care to name, and all for free*.
The vast majority of the buildings require no booking. Just show up on the day and walk in (or join the queue, in the more popular cases). Another subset requires you to book in advance. Finally, a handful of the more popular sites work on a ballot system, whereby you pre-book and then keep your fingers crossed that your name is chosen at random. This year's ballotudians are for tours of 10 Downing Street, The View From The Shard, London Eye and Gray's Inn. Enter the draw here.
Details of the hundreds of buildings are now online. You can narrow your search to your borough (unless you live in Bromley, Harrow or Kingston, who appear to be party pooping), by date and by building type. Say, for instance, you're only interested in exploring military sites, a quick search reveals that you have the Old Royal Military Academy, Woolwich Arsenal Clock Tower and the Neasden bunker at your disposal. For (we think) the first time, a map is embedded to help you plan your weekend of tours. Unfortunately, it's tiny, and not colour-coded by day, so is of limited use.
*Although the programme can be freely browsed online, you're probably better off getting hold of the print copy, to better make sense of the overwhelming options. The price has gone up this year to £7.50, but this still seems a reasonable cost for two whole days of architectural snooping.
We'll return to Open House a week before the event, with our picks of the best buildings to visit.