You should pull up and remove weeds by hand as and when they appear. If it is a regular problem, you might need to reseal the paving. In extreme cases, the sub layer itself may need to be re-laid. You can use weed killer, however some paving can be discoloured by stronger weed killers.
Pencader
Pencader is a little village in the Welsh region of Carmarthenshire, as well as becomes part of the Community and Parish of Llanfihangel-ar-Arth. It lies around 3 miles (5 kilometres) south-east of Llandysul as well as 6.5 miles (10 kilometres) south-west of Llanybydder, in the valley of the Gwen creek, soon prior to the assemblage with the River Talog, to form the River Tyweli (a tributary of the Teifi). It is a quiet village with little bit more than 500 residences, 2 shops, as well as two pubs. Pencader's history returns a long way. For years, it was just one of the main stops on the Carmarthen - Aberystwyth rail path, and was the junction for the service to Newcastle Emlyn; the Pencader Tunnel allowed services to reach Carmathen through Llanpumsaint. The decrease of the railways saw the Newcastle Emlyn branch line closed in 1952 and the main line near passengers in 1965.