Paving slabs... cleaning and filling gaps

[Kells]

Hi there,

I've moved to a house and just had a go at jetwashing the paving slabs. The grey/green surface dirt is coming off but they have all these spots, more in the shady parts, that the jetwash won't get off, see attached pics. Think there's also some oil stains. Any ideas as to what I can do to get them properly clean?

Also second question, in half the patio, the gaps between the slabs haven't been filled in so I've had loads of dirt and weeds growing between. The gaps are around 2cm wide. What's the best thing to fill the gaps with? The easier the better. On my last patio, the guy who laid it put this sandy stuff in the gaps and then watered the top which hardened and did the job great. It looked a lot easier than mixing cement up to the right consistency etc. Any ideas what that was and where I could get it?

Thanks all,

Kelly

Edited March 12, 2022 by Kells
additional info

[Gone West]

1 hour ago, Kells said:

On my last patio, the guy who laid it put this sandy stuff in the gaps and then watered the top which hardened and did the job great.

Might have been this stuff.

 

https://www.everbuild.co.uk/products/landscaping/jointing-compound/sika-fastfix-all-weather/

 

[Redoctober]

We used this on ours and works perfectly - has withstood jet washing twice now - 

 

https://www.amazon.co.uk/Jointing-Compound-Stone-Joint-Mortar/dp/B010V0U5MG

[Kells]

Thanks guys, looks like both of those are the same as I what I was thinking.

 

Now I just need to get the stubborn spots off the paving... anybody know how?

[PeterW]

23 minutes ago, Kells said:

 

 

Now I just need to get the stubborn spots off the paving... anybody know how?

This stuff is good 

 

 

[Kells]

18 hours ago, PeterW said:

This stuff is good 

 

 

That looks like exactly what I need! Thanks!

[SBMS]

On 12/03/2022 at 18:26, Kells said:

Thanks guys, looks like both of those are the same as I what I was thinking.

 

Now I just need to get the stubborn spots off the paving... anybody know how?

So these are usually black lichen spots.  We had them all over the patio (yorkshire stone) of the the last house we were in. I, like you, started looking for a product and came across the (relatively expensive) No More Black spot.  Was going to push the button on it and a commercial cleaner told me that the miracle cure for this is....bleach. As in 79p household bleach.  On a dry sunny day I sprayed the patio and brushed off the excess water. Then I got about 3-6l of bleach and liberally poured a 'glug' (that's a scientific measure) onto each flag.  With an old soft brush, work the bleach up into a light foam - no pressure, just to get it applied to the whole of the face of the stone - and leave it.  Don't rinse it.  Do this for the entire patio.  Be careful at the edges of lawn etc as it'll decimate anything it touches.  I never actually rinsed it off but left it to absorb into the flags.  Next day I would say 90% of the lichen was good.

[Kells]

On 13/03/2022 at 19:28, SBMS said:

So these are usually black lichen spots.  We had them all over the patio (yorkshire stone) of the the last house we were in. I, like you, started looking for a product and came across the (relatively expensive) No More Black spot.  Was going to push the button on it and a commercial cleaner told me that the miracle cure for this is....bleach. As in 79p household bleach.  On a dry sunny day I sprayed the patio and brushed off the excess water. Then I got about 3-6l of bleach and liberally poured a 'glug' (that's a scientific measure) onto each flag.  With an old soft brush, work the bleach up into a light foam - no pressure, just to get it applied to the whole of the face of the stone - and leave it.  Don't rinse it.  Do this for the entire patio.  Be careful at the edges of lawn etc as it'll decimate anything it touches.  I never actually rinsed it off but left it to absorb into the flags.  Next day I would say 90% of the lichen was good.

Yes, I went and bought 5L of expensive stuff for black spots and realised it's just strong bleach and you can at least buy Sodium Hypochlorite which is a lot cheaper than the stuff sold specifically as black spot remover. I guess ordinary household bleach is just as good!

[Kells]

I had a follow up question... The gaps between my slabs are quite large and deep and I was wondering if I could partially fill with sharp sand and top up with the proper filler? To save on cost...?

[Temp]

Until yesterday my India Stone patio hadnt been cleaned for 15 years and was worse than the pictures in the OP. Some were completely black.

 

My small pressure washer would hardly touch it so I looked at renting a big one that would do 3000psi. Ended up buying a Pollor brand 7HP petrol model for not much more than they wanted to charge to hire one.

 

After washing of the dirt with the pressure washer there was still loads of black, white and even some green patches 

 

Then hit it with 15%  Sodium Hypochlorite diluted 50:50 with water. Instructions said to apply it to dry stone so I waited overnight for it to dry after pressure washing. That made an amazing difference. There are still a few black spots but it's come up great overall.

 

Following day after the Sodium Hypochlorite had dried I hit it with Wet and Forget (Ammonium Chloride based) diluted 5:1 with water. Apparently that stuff helps stop it come back. Time will tell.