Patio and monobloc drive power washing

[Clariman]

Two related questions on one post.

I plan to power wash my monobloc driveway next week and have ordered up some fine kiln dried sand to brush into the tiny gaps. Should I use the power washer on full force or a lower setting? Should I blast in the small gaps to remove debris, moss and a few weeds? Anything else I need to know? Do I need to apply anything else afterwards e.g. weedkiller or sealant?

I have already power washed 2 patios. One was well constructed with little or no gap between them so I could perhaps sand those too or just leave them. The other patio has gaps between the slabs - up to a centimetre in places. What should I fill those gaps with?

Thanks
Clariman

[seagles]

According to the "patio" cleaner man I was talking to last week, it needs to be high powered to clear out weeds and soil between the blocks otherwise the weeds will grow back too quickly. Mind you he also pointed out that his high powered industrial cleaner is far better than any power washer.
My housekeeper was bored the other week and cleaned all the gaps in my drive and path with an old knife, did not have the heart to tell her that i was going to get the professionals in.

[sg31]

I used a standard power washer to do my drive when I lived outside Brighton. It was a big area of roughly 400 square metres and there was a decent amount of moss in the joints, a few weeds and a lot of lichen on the paviours. Blasting the sand,moss and weeds out is relatively easy but getting rid of the lichen takes a lot of work. I found one of the fine rotating head jets did the best job. Not the rotating scrubbing brush things just a fine rotating nozzle.

As you proceed you will get a lot of crud on the surface which you can move about with the jet but eventually it gets to the point where you are better moving to work on another area while the first dries out somewhat , then it's easier to remove most of the crud with a brush and shovel.

When you get to the end of the pressure washing leave the area to dry out for a day or more because the gaps hold moisture much longer than the surface. When it's dry enough tip out a bag of kiln dried sand and brush it into the joints. Technically you should use a vibro tamping plate to vibrate the sand into the gaps and tighten the whole drive properly. If you can borrow one that's great but a lot of people don't bother.

I've no experience of the sealants. They are supposed to slow down moss growth by sealing the gaps but I'm not sure how effectively they do so. They might help a little with lichen. If you do go for sealant use one of the more expensive ones. I've seen drives done with cheap ones and I wasn't impressed.

Good luck with it.

[AsleepInYorkshire]

Two related questions on one post.

I plan to power wash my monobloc driveway next week and have ordered up some fine kiln dried sand to brush into the tiny gaps. Should I use the power washer on full force or a lower setting? Should I blast in the small gaps to remove debris, moss and a few weeds? Anything else I need to know? Do I need to apply anything else afterwards e.g. weedkiller or sealant?

I have already power washed 2 patios. One was well constructed with little or no gap between them so I could perhaps sand those too or just leave them. The other patio has gaps between the slabs - up to a centimetre in places. What should I fill those gaps with?

Thanks
Clariman

There are two schools of thought. The first is use a power wash and replace the jointing materials. The second is check the manufacturers guidelines on power washing. Many will say they don't recommend power washing. Which then leaves you with a dichotomy as the only way to remove moss is "chemically".

I have a 20 year old block paved drive. When I was "poorly" and times were tight with money I decided to power wash the drive. I sealed it afterwards too. Total waste of time.

Jeyes Fluid will kill the moss [and weeds I think] and prevent regrowth for 12 weeks. If the drive is particularly bad it may need a second application. Jeyes recommend the application is left on for a period of time and "washed off". I just tip it on and leave it. It smells like creosote.

Just noting that if your drive is wet [and it will be after you've washed it] then you can't apply kiln dried sand until the blocks (and particularly the joints) are dry. Otherwise it will not fall to the bottom of the joint.

Are the joints ranging up to a centimetre deliberate or simply poorly laid - are some joints tight and some wide on the same "patio"?

AiY"t"n'U

[quelquod]

Sadly it’s a hiding to nothing in the longer term. I agree that powering into the gaps is really needed to shift well established weeds but the longer term problem is that heavy duty power washing specially the rotating nozzle type of cleaning steadily destroys the fine surface of the pavers aggravating the issues of moss and lichen growth and damaging the appearance. Chemical cleaning and a non-power hot industrial washer followed by regular Pathclear application IMHO works best, the intensity of power washing to shift lichen and algae is very damaging longer term.

[Dod101]

I agree that power washing is not really an answer. I find that proprietary Patio Cleaners which are applied like weedkiller work but they are very expensive. And never use power washers on roof tiles!

Dod

[Mike88]

For the wider joints on the "other patio" use this:

https://www.screwfix.com/p/cementone-wi ... 20kg/69949

[EssDeeAitch]

I followed a four step process which worked very well.
1. Water drive with a copper sulfate solution to kill lichen. Works very well, and is quick and cheap
2. Power wash on maximum setting (not much in the way of weeds between blocks so used long handled wire brush to clean out)
3. Brush sand into gaps
4. Use Thompsons sealant which was recommended by the people who laid the drive.

Work done in February and so far, so good.

[bungeejumper]

I agree that power washing is not really an answer. I find that proprietary Patio Cleaners which are applied like weedkiller work but they are very expensive.

Nearly all proprietary cleaners (Moss Terminator, Patio Magic) are highly diluted versions of industrial biocide cleaners, primarily BAC and DDAC, which can be obtained online for (relatively) trifling amounts. Very similar to the chemicals used in hospital cleaning.

There was a DAK thread on this a couple of months ago (viewtopic.php?f=9&t=22097) - to cut a long story short, you need a concentration of 1% to 2% to clear a patio of moss and algae, whereas the stuff you can buy for about £10 a litre (or £20 for five litres, as I did) is delivered at 50% strength. You do the maths.

It is, however, very nasty stuff in its concentrated form. It can burn your skin or cause permanent eye damage. I diluted my DDAC wearing the nearest thing I could manage to a hazmat suit. Worked brilliantly at a 2% concentration, though.

And never use power washers on roof tiles!

Especially if you're pointing the power washer upwards. As my friend discovered. Upskwirting, as the tabloids would probably call it.....

BJ

[Clariman]

Thanks everyone. Unfortunately I missed some of the answers so have already gone down the power washing route. One more session this morning and I'll have cleared all the muck and crud off the monobloc. Lots of moss and general muck, but little in the way of lichen.

I'll leave it at least 24 hours before applying the sand. Does anyone have any advice on that part? I can imagine that it will leave the drive with lots of loose sand on top too. Does that just blow away?

As for the large gaps in patio number 2, they were poorly laid during a heavy rain shower. I power washed out all the weeds but they are coming back with a vengeance. I'll maybe use any spare sand there. If not I'll use the stuff suggested above.

Thanks

[Mike88]

In order to correctly use kiln dried sand the areas cleaned need to be absolutely dry. In my view leaving the bricks to dry for 24 hours is not nearly long enough as water will have penetrated the joints. I would wait for at least 3-4 days before applying the kiln dried sand.

[Clariman]

In order to correctly use kiln dried sand the areas cleaned need to be absolutely dry. In my view leaving the bricks to dry for 24 hours is not nearly long enough as water will have penetrated the joints. I would wait for at least 3-4 days before applying the kiln dried sand.

I'll need to keep an eye on the weather. It is exceptionally hot here for this time of year and drive is in full sun all day. I think we might get some rain on Wednesday

[JuanDB]

This website is the best reference I have found for all matters paving related. I've used the advice extensively and it has never let me down.

This link should take you directly to a series on refurbishing a block paved driveway.

https://www.pavingexpert.com/refurbishment-of-a-block-paved-driveway

Cheers,

Juan.

[EssDeeAitch]

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I'll leave it at least 24 hours before applying the sand. Does anyone have any advice on that part? I can imagine that it will leave the drive with lots of loose sand on top too. Does that just blow away?
...........................

Thanks

I brushed the sand in on day one. Brushed the residual sand laying on the drive in again on day two and the same on day three after which there was very little left (Mrs SDH was not surprised it took me three goes as this is my usual performance with interior brushing ). I was surprised at how may gaps between pavers I had missed on the first two sweepings so it was necessary.