To start the building you need to have 15M iron, 10M silver, 2500 Ale, 2000 Timber, 2000 Stones and 100 Scrolls. It i not possible to use Gold for upgrade. Building time for level 1 is 10 days. Only the cheif or any of the Elders can start a construction process, but all clan members can send rss to the Stronghold Resource Storage.
For speeding up the building process or the process you use a Stronghold Boost.
The Carpenters' yard converts Timber into Steel.
For level 1 the stats are
Maximum of Steel received: 2000
Stronghold Influence: +62M
(someone else can make a proper table later)