Read the joints before deciding where to clean
Make a short survey of the blocks from the outside edge inwards. A kerb or border can show where the blocks have started to spread. An area with deeper gaps may look similar from a distance to one with intact joints. Show both so we can assess whether the approach needs to change. Mark a rocking block or a patch that has previously been reset. If the paving continues beyond the area you want washed, show the line where the clean should stop.
Look at the growth around the joints separately from the condition of the blocks. Send a close picture of moss or weed growth and a view from further back to show whether it is concentrated at a border. Where the joints are already loose, discuss what the wash can disturb. Re-sanding is a separate agreed task and resetting or replacing blocks is repair work. Keep those decisions visible in the quotation.
For a section with a mixture of blocks and concrete, name the block-paved part on its own. If a side strip runs beside loose gravel, include its start and end. A note about the finish you expect can help distinguish a wash from a wider job to deal with the condition of the paving. After the assessment, check that both the blocks and any follow-up work are described separately.
Compare a patch with firm joints to the section that concerns you. Take both close-ups from a similar angle and include enough surrounding blocks to locate each patch again. Look for a change in alignment at the edge rather than taking one image of the darkest block. If the intended outcome includes dealing with gaps between the blocks, raise that separately. Ask for the cleaning boundary and the condition notes to be set out before agreeing any follow-up work. Where one strip needs extra care, draw a line on a copy of the picture and mark the start and finish. That gives the wash scope a practical limit on a surface that otherwise looks continuous.
Agree the cleaning boundary and any follow-up
The RHS guidance on algae and moss on hard surfaces describes moss and similar growth on hard surfaces. On block paving, photograph that growth alongside the joint material. Cleaning can loosen material already in the joints. Re-sanding or repair stays separate and only forms part of an agreed written scope where applicable.
