Hello,

My patio (about 25 sq metres) is made of bog-standard concrete slabs laid
about 20 years ago. I have a problem with black stains on the slabs. The
stains are roughly circular, about the size of a small coin, and very
difficult to remove. I suspect they are caused by a fungus or mould in the
slab itself, rather than on the surface.

I've tried patio cleaner solution from a DIY / Garden centre (expensive and
ineffectual). I've tried blasting the slabs with a high-pressure water jet
(shifts the surface dirt nicely, doesn't affect the stains). I've tried
scrubbing with a broom and a variety of scouring / cleaning powders &
liquids (Ajax, Flash, Jif etc).

The only effective method I've found is to scrub the slabs with thick, neat
bleach, leave it for several hours, then rinse it off. It is messy and
time-consuming , requires an awful lot of bleach (about 1 litre of bleach
per sq. metre), and kills the grass at the edge of the lawn (though it soon
recovers). The treatment has to be repeated every year.

Does anyone have any better ideas or suggestions?

Thanks
KK

"KK" wrote in message
...
Hello,

My patio (about 25 sq metres) is made of bog-standard concrete slabs laid
about 20 years ago. I have a problem with black stains on the slabs. The
stains are roughly circular, about the size of a small coin, and very
difficult to remove. I suspect they are caused by a fungus or mould in the
slab itself, rather than on the surface.

I've tried patio cleaner solution from a DIY / Garden centre (expensive and
ineffectual). I've tried blasting the slabs with a high-pressure water jet
(shifts the surface dirt nicely, doesn't affect the stains). I've tried
scrubbing with a broom and a variety of scouring / cleaning powders &
liquids (Ajax, Flash, Jif etc).

The only effective method I've found is to scrub the slabs with thick, neat
bleach, leave it for several hours, then rinse it off. It is messy and
time-consuming , requires an awful lot of bleach (about 1 litre of bleach
per sq. metre), and kills the grass at the edge of the lawn (though it soon
recovers). The treatment has to be repeated every year.

Does anyone have any better ideas or suggestions?

Thanks
KK

How about sealing the slabs with something after you've cleaned them?
Look for concrete sealant via goggle.........

jenny

In article , KK
writes
My patio (about 25 sq metres) is made of bog-standard concrete slabs
laid about 20 years ago. I have a problem with black stains on the
slabs. The stains are roughly circular, about the size of a small coin,
and very difficult to remove. I suspect they are caused by a fungus or
mould in the slab itself, rather than on the surface.

I've tried patio cleaner solution from a DIY / Garden centre (expensive
and ineffectual). I've tried blasting the slabs with a high-pressure
water jet (shifts the surface dirt nicely, doesn't affect the stains).
I've tried scrubbing with a broom and a variety of scouring / cleaning
powders & liquids (Ajax, Flash, Jif etc).
What about Armillatox - under the new regs this is now what it's
labelled to do anyway.
Colin
--
Colin Brook - Winchester (UK)

Tel:+44(0)1962-714030 Fax:+44(0)8701641293 Mobile:07976258703

The treatment has to be repeated every year.

Does anyone have any better ideas or suggestions?


Is it out of the question to seal it with a concrete paint? I used to do my
factory floors with some quite good stuff. I believe it was by a company
called Watco. Comes in all sorts of colours, wears quite well.

Of course it depends on where it is and how you use the patio as to whether
it would be aesthetically pleasing to paint it.

Mike


--
H.M.S.Newfoundland Association Reunion Hayling Island April 23rd - 26th
Royal Naval Reunion Eastbourne May 7th - 10th
H.M.S.Collingwood Association Reunion Bracklesham Bay May 21st - 24th
Nat.Service (RAF) Assoc. Cosford Parade / Social Weekend 25th - 28th June

:-))

http://www.watco.co.uk/

--
H.M.S.Newfoundland Association Reunion Hayling Island April 23rd - 26th
Royal Naval Reunion Eastbourne May 7th - 10th
H.M.S.Collingwood Association Reunion Bracklesham Bay May 21st - 24th
Nat.Service (RAF) Assoc. Cosford Parade / Social Weekend 25th - 28th June

"KK" wrote in message
...
Hello,

My patio (about 25 sq metres) is made of bog-standard concrete slabs laid
about 20 years ago. I have a problem with black stains on the slabs. The
stains are roughly circular, about the size of a small coin, and very
difficult to remove. I suspect they are caused by a fungus or mould in the
slab itself, rather than on the surface.

I've tried patio cleaner solution from a DIY / Garden centre (expensive and
ineffectual). I've tried blasting the slabs with a high-pressure water jet
(shifts the surface dirt nicely, doesn't affect the stains). I've tried
scrubbing with a broom and a variety of scouring / cleaning powders &
liquids (Ajax, Flash, Jif etc).

The only effective method I've found is to scrub the slabs with thick, neat
bleach, leave it for several hours, then rinse it off. It is messy and
time-consuming , requires an awful lot of bleach (about 1 litre of bleach
per sq. metre), and kills the grass at the edge of the lawn (though it soon
recovers). The treatment has to be repeated every year.

Does anyone have any better ideas or suggestions?

Thanks
KK

How about sealing the slabs with something after you've cleaned them?
Look for concrete sealant via goggle.........

jenny

In article , KK
writes
My patio (about 25 sq metres) is made of bog-standard concrete slabs
laid about 20 years ago. I have a problem with black stains on the
slabs. The stains are roughly circular, about the size of a small coin,
and very difficult to remove. I suspect they are caused by a fungus or
mould in the slab itself, rather than on the surface.

I've tried patio cleaner solution from a DIY / Garden centre (expensive
and ineffectual). I've tried blasting the slabs with a high-pressure
water jet (shifts the surface dirt nicely, doesn't affect the stains).
I've tried scrubbing with a broom and a variety of scouring / cleaning
powders & liquids (Ajax, Flash, Jif etc).
What about Armillatox - under the new regs this is now what it's
labelled to do anyway.
Colin
--
Colin Brook - Winchester (UK)

Tel:+44(0)1962-714030 Fax:+44(0)8701641293 Mobile:07976258703

The treatment has to be repeated every year.

Does anyone have any better ideas or suggestions?


Is it out of the question to seal it with a concrete paint? I used to do my
factory floors with some quite good stuff. I believe it was by a company
called Watco. Comes in all sorts of colours, wears quite well.

Of course it depends on where it is and how you use the patio as to whether
it would be aesthetically pleasing to paint it.

Mike


--
H.M.S.Newfoundland Association Reunion Hayling Island April 23rd - 26th
Royal Naval Reunion Eastbourne May 7th - 10th
H.M.S.Collingwood Association Reunion Bracklesham Bay May 21st - 24th
Nat.Service (RAF) Assoc. Cosford Parade / Social Weekend 25th - 28th June

:-))

http://www.watco.co.uk/

--
H.M.S.Newfoundland Association Reunion Hayling Island April 23rd - 26th
Royal Naval Reunion Eastbourne May 7th - 10th
H.M.S.Collingwood Association Reunion Bracklesham Bay May 21st - 24th
Nat.Service (RAF) Assoc. Cosford Parade / Social Weekend 25th - 28th June

"KK" wrote in message
...
Hello,

My patio (about 25 sq metres) is made of bog-standard concrete slabs laid
about 20 years ago. I have a problem with black stains on the slabs. The
stains are roughly circular, about the size of a small coin, and very
difficult to remove. I suspect they are caused by a fungus or mould in the
slab itself, rather than on the surface.

I've tried patio cleaner solution from a DIY / Garden centre (expensive and
ineffectual). I've tried blasting the slabs with a high-pressure water jet
(shifts the surface dirt nicely, doesn't affect the stains). I've tried
scrubbing with a broom and a variety of scouring / cleaning powders &
liquids (Ajax, Flash, Jif etc).

The only effective method I've found is to scrub the slabs with thick, neat
bleach, leave it for several hours, then rinse it off. It is messy and
time-consuming , requires an awful lot of bleach (about 1 litre of bleach
per sq. metre), and kills the grass at the edge of the lawn (though it soon
recovers). The treatment has to be repeated every year.

Does anyone have any better ideas or suggestions?

Thanks
KK

How about sealing the slabs with something after you've cleaned them?
Look for concrete sealant via goggle.........

jenny

In article , KK
writes
My patio (about 25 sq metres) is made of bog-standard concrete slabs
laid about 20 years ago. I have a problem with black stains on the
slabs. The stains are roughly circular, about the size of a small coin,
and very difficult to remove. I suspect they are caused by a fungus or
mould in the slab itself, rather than on the surface.

I've tried patio cleaner solution from a DIY / Garden centre (expensive
and ineffectual). I've tried blasting the slabs with a high-pressure
water jet (shifts the surface dirt nicely, doesn't affect the stains).
I've tried scrubbing with a broom and a variety of scouring / cleaning
powders & liquids (Ajax, Flash, Jif etc).
What about Armillatox - under the new regs this is now what it's
labelled to do anyway.
Colin
--
Colin Brook - Winchester (UK)

Tel:+44(0)1962-714030 Fax:+44(0)8701641293 Mobile:07976258703

The treatment has to be repeated every year.

Does anyone have any better ideas or suggestions?


Is it out of the question to seal it with a concrete paint? I used to do my
factory floors with some quite good stuff. I believe it was by a company
called Watco. Comes in all sorts of colours, wears quite well.

Of course it depends on where it is and how you use the patio as to whether
it would be aesthetically pleasing to paint it.

Mike


--
H.M.S.Newfoundland Association Reunion Hayling Island April 23rd - 26th
Royal Naval Reunion Eastbourne May 7th - 10th
H.M.S.Collingwood Association Reunion Bracklesham Bay May 21st - 24th
Nat.Service (RAF) Assoc. Cosford Parade / Social Weekend 25th - 28th June

:-))

http://www.watco.co.uk/

--
H.M.S.Newfoundland Association Reunion Hayling Island April 23rd - 26th
Royal Naval Reunion Eastbourne May 7th - 10th
H.M.S.Collingwood Association Reunion Bracklesham Bay May 21st - 24th
Nat.Service (RAF) Assoc. Cosford Parade / Social Weekend 25th - 28th June

"KK" wrote in message
...
Hello,

My patio (about 25 sq metres) is made of bog-standard concrete slabs laid
about 20 years ago. I have a problem with black stains on the slabs. The
stains are roughly circular, about the size of a small coin, and very
difficult to remove. I suspect they are caused by a fungus or mould in the
slab itself, rather than on the surface.

I've tried patio cleaner solution from a DIY / Garden centre (expensive and
ineffectual). I've tried blasting the slabs with a high-pressure water jet
(shifts the surface dirt nicely, doesn't affect the stains). I've tried
scrubbing with a broom and a variety of scouring / cleaning powders &
liquids (Ajax, Flash, Jif etc).

The only effective method I've found is to scrub the slabs with thick, neat
bleach, leave it for several hours, then rinse it off. It is messy and
time-consuming , requires an awful lot of bleach (about 1 litre of bleach
per sq. metre), and kills the grass at the edge of the lawn (though it soon
recovers). The treatment has to be repeated every year.

Does anyone have any better ideas or suggestions?

Thanks
KK

How about sealing the slabs with something after you've cleaned them?
Look for concrete sealant via goggle.........

jenny

In article , KK
writes
My patio (about 25 sq metres) is made of bog-standard concrete slabs
laid about 20 years ago. I have a problem with black stains on the
slabs. The stains are roughly circular, about the size of a small coin,
and very difficult to remove. I suspect they are caused by a fungus or
mould in the slab itself, rather than on the surface.

I've tried patio cleaner solution from a DIY / Garden centre (expensive
and ineffectual). I've tried blasting the slabs with a high-pressure
water jet (shifts the surface dirt nicely, doesn't affect the stains).
I've tried scrubbing with a broom and a variety of scouring / cleaning
powders & liquids (Ajax, Flash, Jif etc).
What about Armillatox - under the new regs this is now what it's
labelled to do anyway.
Colin
--
Colin Brook - Winchester (UK)

Tel:+44(0)1962-714030 Fax:+44(0)8701641293 Mobile:07976258703