[5] The building was opened in 1991 and has a total floor area of 11,583 m2 (124,680 sq ft).

It is built of red brick and is connected to the Senedd debating chamber in Cardiff Bay.

Crickhowell House was used as a temporary debating chamber for the National Assembly for Wales from 1999 until its new building, also originally known as the Senedd, was opened in 2006.

On 25 June 2008 the Prince of Wales officially opened Siambr Hywel, the National Assembly's youth debating chamber and education centre, based on the former debating chamber in Tŷ Hywel.

[7][9] Two covered link bridges connect the Senedd building to Tŷ Hywel.