Maintaining block paving and Indian stone flags - what not to do

Caring for your new driveway or patio should be quite straightforward, but there are a number of common pitfalls that can end up reducing both the look and performance of your paving that should be avoided at all costs. This page will first outline what NOT to do, followed by some really simple steps that can be taken to care and maintain without doing harm.

The most important rule - the golden rule - basically the only rule - do NOT be tempted to use a power washer! That also includes not letting a "professional" 3rd party loose with one either!

If you take one away from reading this article let it be this: power washing is destructive and should be avoided at all costs. It's tempting when results can appear to be instantly transformative with a simple, cathartic sweep of the lance, but real harm can easily be done to not only the paving's surface (I've seen a petrol-powered power washer rip the surface from polished sandstone steps and copings) but also the all-important jointing material and therefore structural integrity of the paving as a whole. Whether a straight nozzle or specially angled "surface cleaning" rotary attachment, it's all harmful and should always be avoided.

Do it once and risk forever being locked into a depressing cycle of chasing the impossible. Damaged paving surfaces and exposed aggregates will only encourage further moss and grime build-up. Joints, now devoid of their clean, hard-wearing materials, become contaminated with what was once mere surface grime but, deposited into the depths of exposed joints, now becomes the ideal fertiliser to encourage invasive plant material to flourish. It's self-defeating. The length of time it takes between cleans will shorten each time as more harm is done and more grime is encouraged.

How block paving is installed

Below is a cross-section of a block-paved driveway:

A lot of time, effort and expense goes into installing paving to these standards. It might not be instantly obvious when looking at that diagram, but the jointing material is of paramount importance - every bit as necessary to the overall performance as all that compacted MOT or the geotextile beneath - and that's why I always apply jointing sand stabiliser to fresh installs as standard.

Kiln-dried sand

Towards the end of their works, installers sweep & compact fine kiln-dried sand into joints and, as they smooth out the finish surface (blocks are made to tolerances that the compactor does away with), they're also tightly locking paviours together (yet also retaining a degree of flexibility that could have other paving materials crack (concrete) or permanently sink (tarmac) under load - this is one of a great many benefits of properly installed modular paving).

That small amount of surface grime that builds up on any paved surface over time (depicted in the diagram above as a thin, green, barely-visible layer) is a trivial problem to contend with. Nothing beneath that grime is in any way in need of disturbing or disruption, but that's exactly what power washing risks.

The above diagram depicts what happens when block paving is power-washed. The surface of the blocks may now appear cleaner, but a good amount of the jointing material is done away with and a degree of surface slurry left behind where it once sat tightly compacted into the void. Topping up with new kiln-dried sand merely locks that sludge down below where it both detracts from performance and promotes weed growth:

Worse still, more excessive power washing can remove a portion of even the bed around the joints, leading to an obvious greater degree of performance issues as the paviours become massively undermined.

Power washing is NEVER worth the risks it poses when other, far simpler solutions exist.


Paving maintenance dos and don'ts

Maintaining block paving and Indian stone flags - simple, effective care

The best way to maintain paving is simply using a stiff brush a couple of times a year and topping up any missing kiln-dried sand or damaged jointing material. Then, every couple of years:

I've found the best way to remove grime and moss from the surface of paving is good old bleach and water. With a few precautions it can be safe and highly effective.

Sold as a swimming pool chlorination solution or patio cleaning/weed control solution, it can quickly and effectively restore dirty paving to a fresh, as-new appearance, even removing black spots and other stains.

1. Sweep off leaves and other detritus, then dampen paving surface.

2. Wear appropriate PPE - gloves and eye-wear.

3. Take an old watering can I use only for this purpose.

4. Fill can to about 3/4 or 2/3 with water.

5. Top up to full with strong bleach.

6. Apply evenly to surface of paving, taking care not to splash on plants and lawns. It begins to effervesce instantly.

7. Take a stiff brush and agitate any of the worst-offending areas lightly.

8. 20-30 minutes later swill down with clean water, taking care to direct any run-off into gravel or other areas where possible.

Job done.

The small cost of a few litres of strong bleach is easily offset against what could have been thousands of litres of clean water from the tap, electricity or petrol powering a power washer and all that expensive replacement kiln-dried sand once everything has dried up - with the added benefit of no harm done to the paving!