Sandstone Patio Cleaning
and Re-Jointing
in Oxford, Oxfordshire

Because some sections had already failed while others remained sound, the old material was carefully cut out using angle grinders. The joints were then cleaned and prepared to create a consistent depth and clean cavity for the new jointing compound.

Carrying out this preparation before the final repointing allowed us to address the patio properly rather than simply filling over deteriorated material.

The most significant cleaning challenge was the amount of established black spot across the sandstone. Our approach to chemical treatment of natural stone is deliberately progressive. Rather than immediately applying an unnecessarily strong treatment, we begin at a lower concentration, assess the response of the individual stone and increase treatment strength only where the contamination requires it.

Carole’s patio ultimately required four to five separate targeted treatment stages. Each application progressively reduced the established black spot, organic staining and surface dullness while allowing us to maintain control over the treatment of the sandstone.

Cleaning alone would not have addressed the movement we identified in several slabs. Two to three loose sandstone slabs were therefore lifted and re-laid to restore stability before the patio was repointed. This was an important structural step: installing new jointing around paving that was still moving would have compromised the longevity of the finished work.

By stabilising the affected slabs first, we could proceed to the new jointing with a sounder paving surface.

Once the paving had been cleaned, treated and stabilised, the patio was completely re-jointed using our preferred resin-based jointing compound. The compound was worked across the sandstone surface and into the prepared joints to create a consistent finished joint system.

As part of that installation process, the resin also enriched the appearance of the sandstone, accentuating the remarkable purple, orange and warm natural tones that had been uncovered during cleaning.

Extensive established black spot and organic contamination had been progressively treated and removed, moss growth around the brickwork had been addressed, loose slabs had been stabilised and the complete patio had been professionally repointed.

Most strikingly, the clean revealed the sandstone’s unusual natural palette of purple, orange and warm mineral tones. The resin-based jointing process further enriched those colours and helped give the completed patio a much more defined, finished appearance.

The result was particularly satisfying because the true appearance of the sandstone had been difficult to predict at the beginning of the project. Years of contamination had concealed a highly distinctive natural stone surface whose colour and variation only became apparent as the clean progressed.

Chiltern Surface Co carried out this sandstone patio restoration and repoint in Oxford, Oxfordshire. We also offer patio cleaning, driveway cleaning, roof cleaning and roof moss removal across Buckinghamshire and Berkshire, including Marlow, Beaconsfield, Ascot and Bracknell.

Carole’s project demonstrates why heavily soiled natural stone often requires a proper cleaning process rather than a single pressure-washing visit.

For this sandstone patio in Oxford, the work combined joint removal and preparation, progressive black spot treatment, sandstone cleaning and brightening, moss removal, slab repairs, complete resin-based repointing and Chiltern EverGuard™ biocide treatment.

It also demonstrates an important principle behind our approach to natural stone: treatment strength should be determined by how the individual surface responds. Starting at a lower concentration and building progressively allowed us to tackle severe black spot through four to five treatment stages rather than relying on an unnecessarily aggressive first application.

The result was not simply a cleaner patio, but the recovery of a distinctive natural sandstone surface whose colour, stability and finished jointing had all been restored.