Many companies and home owners have installed a joint material in patios which is wetted and then brushed into the paving. It looks great when new and its super quick and easy to install, but it is porous and in time it will break down and start to leave holes in the patio joints as well as allowing weeds to grow. Aside from this it can prove detrimental to the patio base.  Porcelain and stone should be laid on a full bed of sand and cement and allowing water down will increase the risk of water becoming trapped and slabs popping. We can fix this by raking and cleaning out the joints and then installing a concrete based grout that will not break down. It has been used for 30 years in the UK and Ireland. Patio repairs are often required to refix loose paving.