Block paving staining help, not coming off

[wakewaterblue]

I have some paving in my garden pathway, made from what I believe to be, Tobermore Sienna block paving as a closest match guess. I have 2 colours of grey and a friend of mine who runs a professional cleaning company, cleaned the paving up using his jetwash setup with hypochlorite. The paving has come up amazing however there is one section which has not cleaned up at all. Before we sand and seal it, we want to try and get this mark off as this is the main area we wanted to sort! Pictures attached.

He cannot get the staining off and has asked around to people in his industry but they don't know the answer. It could be some previous sealant used, the gaps seem to be quite hard and I've even scrubbed and scrubbed in the past but nothing changed. It's just odd it's that section alone, it is slightly sheltered compared to the rest of it but I live on the coast and we get battered weather wise, but it's not out of the elements completely. An idea was to turn the blocks over to the fresh aide, however they are different on the other side, smooth and without a curved edge I believe so that isn't possible which is real shame!

 

Any ideas what I can try and use to treat it with? If it's some sort of sealant, what might cut through it? 

 

I want to try this first before buying replacements as I will need to cut them to size... I do have an angle grinder but that is a last resort for me.

 

Thanks!

[nod]

It will cost you about £25 m2 To replace the blocks For £25 I’d replace the stained blocks 

[FarmerN]

Can you lift a stained block out to experiment on?

Try different things. Brick acid, very strong hypochlorite /washing up liquid mix, different solvents ? Apply and leave to soak rather than scrub.

Care needed ! Don’t mix chemicals!

Good Luck.

[wakewaterblue]

Thank you for your replies. On further investigation the only logical conclusion is that this is some old sealant that has discoloured from UV exposure. It's a bit more sheltered in that area so perhaps it's just degraded slower or perhaps a different type of sealant was put down in that area by the builders. I may never know the answer! I bought this property from new and have never had the paving cleaned or sealed until now, so before it gets sanded and sealed, I will try to sort this. The blocks were likely put down about 14-15 years ago.

 

Hypochlorite was put on it for the jet wash clean and left on for decent time, it was like it was resistant to it and the jet wash power didn't cut through it, like a sealant would behave. 

 

I have purchased a special sealant remover for paving, so I will try that on one of the blocks first and see how it comes up and how much effort / time it takes. However, I think you are right in that it might be easier to replace the individual stained blocks! 

 

On my research, I think my paving blocks are Marshalls Argent? I know they come in a large mixed pack but I can see there is dark grey along the window edge in rectangles and the rest are the square light grey. Do places sell these blocks individually?

 

Many thanks all 

[gaz_moose]

can you try taking one out to see if you can just turn them over? this will depend on how they have been laid.

[Temp]

Jewson appear to sell Marshalls Argent in 450x450. Might only be whole packs but check.

 

[Temp]

Some on eBay check size..

 

https://ebay.us/m/Cvw9ok

Edited June 15 by Temp

[MPH243]

Could you swap the ones in the corner for the ones further out ( if they are the same size).

They would then weather and walking would possibly clean them up if you can't replace them.

[wakewaterblue]

I believe my slabs are from a mixed pack as I have 160x160mm ones mostly, some halves and some rectangle. I will have to see if any merchants sell them loose. 
 

I believe them to be smooth and flat on the other side. Otherwise I would do that in a flash! 
 

I could swap some around yes but when I actually counted how many were actually affected it was a lot!!

I will let you know how I get on with this sealant remover and go from there. Thanks all 

 

[wakewaterblue]

I believe my slabs are from a mixed pack as I have 160x160mm ones mostly, some halves and some rectangle. I will have to see if any merchants sell them loose. 
 

I believe them to be smooth and flat on the other side. Otherwise I would do that in a flash! 
 

I could swap some around yes but when I actually counted how many were actually affected it was a lot!!

I will let you know how I get on with this sealant remover and go from there.

 

 

 

[wakewaterblue]

Also on another note. When they jet washed, it must have forced some of what appears to be mortar at the front under the full floor to ceiling window and door, to the other side. Looks like sand has come through under the skirting. 
 

I replaced this skirting some years ago as it was MDF which had got wet I think from either outside sneaking in over time or the floor being mopped. 
 

When I removed the damaged skirting, I could see a bit of a void under the window door frame so I sprayed some expanding foam filler in, trimmed it up and then put wood skirting back on. 
 

What would you say is going on at the front here? I was an apprentice brickie but only did the training so no expert. Seems some sort of mortar, with a damp proof membrane? 
 

I believe my building is concrete,  a 4 storey block built about 14 years ago. 
 

Should I put in more expanding foam from the outside? I’m conscious that will not be attractive from the front and it’s not really what I want to see! Or should I put some mortar in there or something? How should it have been finished?

[Ferdinand]

@wakewaterblue, On your "sand blown through under the patio window last point":

My suggestion for the outside gap would be waterproof mortar - that is a specialised product, or use an additive. There may be merit in clearing out what is there already to get a thicker new section rather than just patching - the gap looks narrow.

At a trivial level, that could be mix in a good amount of PVA (I have used this eg in small added slabs filling in old chimneys breasts), or something more specialised.

Make sure that the surface slope leads moisture away from the house, but you know that I'm sure.

To tidy it up you could colour the mortar if you clear it all out, or use a plastic L section over the top, which can be obtained coloured.

That should give you imo a 10-25 year repair, done carefully.

[Ferdinand]

On your original query, I think I might be inclined to accept it as what happens with different weather exposure near the coast.

Do you know it won't just happen again with the next lot of blocks?

I think I would possibly just leave it, and install a large entrance mat * or textured covering over the entire recessed area. It's a place to make sure no mud etc gets in, a place for outdooor pot plants etc, and can just be hosed down if necessary. I'd go for a domestic-looking commercial grade one and cut it to size.

Were I redoing blocks, rather than go for pristine in a situation which might be naturally impossible to keep pristine, I might go for a contrast for the recess and eg make the whole thing dark blue (which imo should have been part of the design as they should understand how it will wear). So the block design and colour layout becomes more immune to the effect you have now seen.

But then I'm the bloke who does not buy white cars because I don't want to have to wash the damn thing every month.

* This sort of thing - an example not a recommendation.
/

[marshian]

Brick acid will normally take off sealant - however it is very aggressive stuff - A friend of mine arrived on my driveway in a car leaking a lot of very hot transmission fluid - it went straight past the sealant on the brickweave and all the normal gunk/jizer oil removal preparations did nothing - brick acid worked but it's obvious which bricks were treated - the surface finish is very different

[wakewaterblue]

On 15/06/2025 at 09:00, gaz_moose said:

can you try taking one out to see if you can just turn them over? this will depend on how they have been laid.

Sadly they are completely different and flat on the other side. Such a shame as that would have solved it 

[wakewaterblue]

Well solvent remover didn’t work. To be fair I didn’t get the strong stuff as it only came in a massive container and was expensive. So I probably didn’t have strong enough stuff. 
 

My friend who did the jet wash, left some rust remover called Smelly Gel Pro which the name suggested, absolutely reeked of rotten eggs! 
 

Put it on some rust marks, got most of that off and it turns red when it does its magic. Decided to try that on some of the paving slabs for a go, it started to turn red and I left it but alas no it didn’t work. Thought it was a long shot given what the liquid is designed for. 
 

Next step is brick acid!