The patio that I am re doing at present was laid on spots with a ballast sub base and black clay sub grade.
It's only 5 years and looks a bloody mess.
Only ever had one argument over spots but the bloke was long in the tooth and agreed with me on completion.
Is my new patio ruined??? - Spot bedding marks.
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McGinty
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- Joined: Tue Jun 09, 2015 5:16 am
- Location: Essex
At risk of asking a silly question, will a full bed stop the staining? Or is it another issue causing them? Will a full bed just cause staining on all the patio as aposed to just over the dabs?sy76uk wrote:The patio that I am re doing at present was laid on spots with a ballast sub base and black clay sub grade.
It's only 5 years and looks a bloody mess.
Only ever had one argument over spots but the bloke was long in the tooth and agreed with me on completion.
McGinty
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Tony McC
- Site Admin
- Posts: 8346
- Joined: Mon Jul 05, 2004 7:27 pm
- Location: Warrington, People's Republic of South Lancashire
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I've just completed a court report on a badly spot-stained patio and to summarise: there is no excuse nor defence for spot bedding. It's wrong on so many levels.
Laying on a full bed is structurally better, but it also minimises reflective staining by providing a homogenous bed rather than one that is part mortar and part fresh/stale air. The staining caused by spot bedding has a number of contributory factors - the wicking and mineralisation mentioned by London Stone is just one factor. There is also a problem with spots affecting porosity in localised 'spots', which has a knock-on effect with colonisation by algae and lichens, not to mention the attraction of dirt and detritus.
With some highly porous stone (Mint is a particular example) it's less a case of a full bed not staining, but that the stain is consistent throughout the stone and therefore not really noticeable. It will, as mentioned, eventually weather out, but we are finding projects which were spot-bedded a decade ago where you can still make out the staining, even if it isn't as blindingly obvious as it was in the first 3-24 months.
The key to educating contractors who believe spot bedding is acceptable is to sue them. Once a court has ordered them to reimburse your considerable costs, they tend to think twice before using spot bedding again. Either that, or they go back to working on a market stall/driving a taxi/window cleaning or whatever it was they did before they decided they were a self-appointed "paving specialist".
Laying on a full bed is structurally better, but it also minimises reflective staining by providing a homogenous bed rather than one that is part mortar and part fresh/stale air. The staining caused by spot bedding has a number of contributory factors - the wicking and mineralisation mentioned by London Stone is just one factor. There is also a problem with spots affecting porosity in localised 'spots', which has a knock-on effect with colonisation by algae and lichens, not to mention the attraction of dirt and detritus.
With some highly porous stone (Mint is a particular example) it's less a case of a full bed not staining, but that the stain is consistent throughout the stone and therefore not really noticeable. It will, as mentioned, eventually weather out, but we are finding projects which were spot-bedded a decade ago where you can still make out the staining, even if it isn't as blindingly obvious as it was in the first 3-24 months.
The key to educating contractors who believe spot bedding is acceptable is to sue them. Once a court has ordered them to reimburse your considerable costs, they tend to think twice before using spot bedding again. Either that, or they go back to working on a market stall/driving a taxi/window cleaning or whatever it was they did before they decided they were a self-appointed "paving specialist".
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