A year ago I had my drive block-paved. I understand they are
'Marshalls' on hardcore plus 'membrane' plus sand. They replaced
mainly the original concrete slabs, and a small stretch of lawn.
Here's a photo:

http://i154.photobucket.com/albums....341.jpg

Overall I'm pleased with the job. But after a long enough dry spell
early this year I noticed that a score or so of the bricks seemed to
have dark patches, as if they were permanently damp. Most of these
were near the garage entrance, just in front of the drain, as shown
he

http://i154.photobucket.com/albums....cks.jpg

Note that the marks remained identical, not varying at all. (That
photo was taken about 2 months ago, yet that area looked exactly the
same yesterday morning.) So I have been assuming that the bricks were
flawed.

To cut to the quick, it's taken me until yesterday afternoon to get
the paver to replace them with new bricks. ("Next week, I promise...",
"Tomorrow...", etc, since April!) He rushed it and missed 3 that
needed replacing, but as he left me some spares I replaced those
myself afterwards.

However I now see that the sand in this area is very wet. Despite
having had a few days without rain. So could it be that that's the
main cause, not any significant flaw with these particular bricks? Are
there perhaps always some porous areas in these bricks that allow
moisture to seep through, and darken the top surface in specific
patches like this?

If so, presumably this means rainwater is not draining away
sufficiently at this small area? So how should I fix that please?
Frankly, I don't want the hassle of getting the paver back yet again,
so want to do it myself. Can I just remove a few bricks and puncture
the membrane in a couple of spots? Would I need to first remove the
wet sand and replace it with dry, or would it eventually dry out
anyway? I doubt my skill at getting it level again if I do so!

Any advice would be much appreciated please.

--
Terry, East Grinstead, UK

Terry Pinnell wrote:

http://i154.photobucket.com/albums....341.jpg
http://i154.photobucket.com/albums....cks.jpg

Something has broken your URLs

Andy Burns wrote:

Terry Pinnell wrote:

http://i154.photobucket.com/albums....341.jpg
http://i154.photobucket.com/albums....cks.jpg

Something has broken your URLs

Strange, thanks for letting me know Andy. They seemed OK when I
checked before posting, but something must have screwed up. Here they
are again. I can click these in my message composition window and they
both open OK:

http://i154.photobucket.com/albums/s...314-083341.jpg
http://i154.photobucket.com/albums/s...-BadBricks.jpg

--
Terry, East Grinstead, UK

Terry Pinnell wrote:
Andy Burns wrote:

Terry Pinnell wrote:

http://i154.photobucket.com/albums....341.jpg
http://i154.photobucket.com/albums....cks.jpg
Something has broken your URLs

Strange, thanks for letting me know Andy. They seemed OK when I
checked before posting, but something must have screwed up. Here they
are again. I can click these in my message composition window and they
both open OK:

http://i154.photobucket.com/albums/s...314-083341.jpg
http://i154.photobucket.com/albums/s...-BadBricks.jpg

Could it be that the drainage channel (visible in the picture) is
preventing flow from the paved area?

Not suggesting you actually do this, but if you lifted the grilles and
drilled holes sideways towards the paved area, would that allow water
from underneath to drain away? Are the drainage channels bedded onto
some mortar which makes them an impenetrable barrier? Of course, this
would only be likely if you have something like clay below everything.

We certainly have some areas that dry out much more readily than others.
But nothing quite as permanent as you describe.

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

Terry Pinnell wrote:

are again. I can click these in my message composition window and they
both open OK:

http://i154.photobucket.com/albums/s...314-083341.jpg
http://i154.photobucket.com/albums/s...-BadBricks.jpg

They basically look waterlogged... are there any drains or gullys in
area that could be leaking?

Where does that linear drain connect to?

Do you know what type of membrane was used in the construction (and in
particular was is something impermeable?)

--
Cheers,

John.

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John Rumm wrote:
Terry Pinnell wrote:

are again. I can click these in my message composition window and they
both open OK:

http://i154.photobucket.com/albums/s...314-083341.jpg
http://i154.photobucket.com/albums/s...-BadBricks.jpg


They basically look waterlogged... are there any drains or gullys in
area that could be leaking?

it looks from the first photo that these are on the lowest point on the
drive, and the drain/membrane is actually preventing the water going any
further that's under the bricks
Where does that linear drain connect to?

Do you know what type of membrane was used in the construction (and in
particular was is something impermeable?)



--
Kevin R
Reply address works

Rod wrote:

Terry Pinnell wrote:
Andy Burns wrote:

Terry Pinnell wrote:

http://i154.photobucket.com/albums....341.jpg
http://i154.photobucket.com/albums....cks.jpg
Something has broken your URLs

Strange, thanks for letting me know Andy. They seemed OK when I
checked before posting, but something must have screwed up. Here they
are again. I can click these in my message composition window and they
both open OK:

http://i154.photobucket.com/albums/s...314-083341.jpg
http://i154.photobucket.com/albums/s...-BadBricks.jpg

Could it be that the drainage channel (visible in the picture) is
preventing flow from the paved area?

Not suggesting you actually do this, but if you lifted the grilles and
drilled holes sideways towards the paved area, would that allow water
from underneath to drain away? Are the drainage channels bedded onto
some mortar which makes them an impenetrable barrier? Of course, this
would only be likely if you have something like clay below everything.

We certainly have some areas that dry out much more readily than others.
But nothing quite as permanent as you describe.

Rod, John, Kevin:

Thanks all. I'm not really sure exactly what the arrangement is near
the drain, but I'm guessing it looks like this in cross section:

http://i154.photobucket.com/albums/s...icksDrain2.jpg

That suggestion of Rod's makes sense, especially as there *is* a lot
of clay here. I don't see that it could do any harm anyway to drill
holes in the drain walls, and hopefully it will allow any excess water
to flow into it.

A key question is whether the membrane is waterproof or not (the
latter I understand being called a 'permeable membrane'). The quote
wasn't explicit on that. But if it was impermeable, wouldn't that mean
that *all* the bricks over the sloping drive would be showing the same
'dampness marks'? Not just this tiny proportion near the drain? On the
other hand, how can a permeable membrane protect against weeds?

The drain simply drops down at its RH end and runs under the garage to
some soakaway point somewhere in the back garden.

The possibility that Rod and Kevin have suggested, that the drain is
somehow blocking proper drainage at the bottom of the drive, seems to
be a logical one to me. I wonder if drilling a dozen 10 mm holes on
that side will solve it? Assuming I *can* get the drill in at that
angle, and that there's no significant obstruction, like cement.

--
Terry, East Grinstead, UK

Terry Pinnell wrote:

A key question is whether the membrane is waterproof or not (the
latter I understand being called a 'permeable membrane'). The quote
wasn't explicit on that. But if it was impermeable, wouldn't that mean
that *all* the bricks over the sloping drive would be showing the same
'dampness marks'? Not just this tiny proportion near the drain? On the

Probably only those near the bottom of the slope.

other hand, how can a permeable membrane protect against weeds?

The purpose of the membrane is not to stop weeds anyway (a popular
misconception). 150mm+ of compacted limestone chippings (aka Type 1 MoT)
will stop any weeds. The membrane is designed to stop the sub base from
migrating into the sub soil.

http://www.pavingexpert.com/faqmembr.htm

The drain simply drops down at its RH end and runs under the garage to
some soakaway point somewhere in the back garden.

A point worth checking is does the soakaway actually work? i.e. if you
stick water in the channel, does it empty easily?

The possibility that Rod and Kevin have suggested, that the drain is
somehow blocking proper drainage at the bottom of the drive, seems to
be a logical one to me. I wonder if drilling a dozen 10 mm holes on
that side will solve it? Assuming I *can* get the drill in at that
angle, and that there's no significant obstruction, like cement.

If the channel empties easily, then it may indeed be the channel (or its
bases - they are usually bedded onto a coarse concrete mix) that is
blocking the exit of water from the bedding layer of the blocks.

See the pavingexpert site linked to above for chapter and verse on
everything to do with block paving .

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote:

Terry Pinnell wrote:

A key question is whether the membrane is waterproof or not (the
latter I understand being called a 'permeable membrane'). The quote
wasn't explicit on that. But if it was impermeable, wouldn't that mean
that *all* the bricks over the sloping drive would be showing the same
'dampness marks'? Not just this tiny proportion near the drain? On the

Probably only those near the bottom of the slope.

other hand, how can a permeable membrane protect against weeds?

The purpose of the membrane is not to stop weeds anyway (a popular
misconception). 150mm+ of compacted limestone chippings (aka Type 1 MoT)
will stop any weeds. The membrane is designed to stop the sub base from
migrating into the sub soil.

http://www.pavingexpert.com/faqmembr.htm

I see, thanks. The paver had included a phrase like "...membrane to
stop weeds" in his quote and I had indeed been labouring under that
misconception!

The drain simply drops down at its RH end and runs under the garage to
some soakaway point somewhere in the back garden.

A point worth checking is does the soakaway actually work? i.e. if you
stick water in the channel, does it empty easily?

Yes, it's working OK.

The possibility that Rod and Kevin have suggested, that the drain is
somehow blocking proper drainage at the bottom of the drive, seems to
be a logical one to me. I wonder if drilling a dozen 10 mm holes on
that side will solve it? Assuming I *can* get the drill in at that
angle, and that there's no significant obstruction, like cement.

If the channel empties easily, then it may indeed be the channel (or its
bases - they are usually bedded onto a coarse concrete mix) that is
blocking the exit of water from the bedding layer of the blocks.

That sounds like an accurate diagnosis to me, thank you. It poses the
issue of what to do about it, of course! I was thinking of simply
lifting the damp bricks and hammering a long screwdriver or something
down to make holes in the membrane and also open up the hard-core a
bit. But we have a lot of clay here, so I'm not sure how effective
that would be. Hence the idea of trying to get the excess into the
shallow drain by drilling holes in the side. Although if there's a lot
of surrounding cement that might be difficult. And anyway the water is
presumably lying well below the level of such holes, which at most
would be about 3-5 cm below the top surface.

BTW, here's another photo (cropped from an original), apparently
showing the membrane between the sand and the hard-core.

http://i154.photobucket.com/albums/s...ksMembrane.jpg

See the pavingexpert site linked to above for chapter and verse on
everything to do with block paving .

Excellent site!

--
Terry, East Grinstead, UK

Terry Pinnell wrote:

If the channel empties easily, then it may indeed be the channel (or its
bases - they are usually bedded onto a coarse concrete mix) that is
blocking the exit of water from the bedding layer of the blocks.

That sounds like an accurate diagnosis to me, thank you. It poses the
issue of what to do about it, of course! I was thinking of simply
lifting the damp bricks and hammering a long screwdriver or something
down to make holes in the membrane and also open up the hard-core a
bit. But we have a lot of clay here, so I'm not sure how effective
that would be. Hence the idea of trying to get the excess into the
shallow drain by drilling holes in the side. Although if there's a lot
of surrounding cement that might be difficult. And anyway the water is
presumably lying well below the level of such holes, which at most
would be about 3-5 cm below the top surface.

How about lifting one or two of the soaked blocks, and then excavating
the sand under it down to the Type 1 base. Then have a look and see if
water pools there (stick a board over it to stop rain falling directly
into the hole!)

If water is pooling in the space were the sand is, then you can see at
what level you would need to arrange a drain.

BTW, here's another photo (cropped from an original), apparently
showing the membrane between the sand and the hard-core.

http://i154.photobucket.com/albums/s...ksMembrane.jpg

Ah, yup, that looks like a sheet of visqueen DPM or something similar.
Completely the wrong thing to use. I would guess that your bedding layer
is totally full of water at the bottom of the slope.

You may find that puncturing the sheet allows enough to flow out of the
sodden area, but then again it might not. No harm in trying though.


(I also note that the edging course of charcoal blocks have not beed
bedded onto a concrete haunch and are just sat on sand. That means there
is no proper restraint at the edge and the whole edge could fall away.
Again have a look at the pavingexpert site for details of how the edge
should be done)


--
Cheers,

John.

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| Internode Ltd - http://www.internode.co.uk |
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| John Rumm - john(at)internode(dot)co(dot)uk |
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