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Posted: Wed Nov 03, 2010 8:41 pm
by jonsey24
Hi all i am in the middle of having my front garden block paved, the fella's doing it have done a good job but the wet weather has hampered their progress over the past 2 days, my question is how wet if at all can the sand used for the bed be when laying blocks, is it best to have no moisture at all or will a little be ok, there is the last section to lay now approx 10sqm but they dont want to do anything till the sand has dried out
Posted: Wed Nov 03, 2010 8:44 pm
by ilovesettsonmondays
either buy some more sand or let it dry out
Posted: Thu Nov 04, 2010 11:44 am
by DNgroundworks
Ive just been watchin some fellas lay a blockpaved drive in the torrential rain round the back of my grans house in lancs, cant wait till they wack it 
Posted: Thu Nov 04, 2010 12:22 pm
by Aitch
DN,
if the bedding sand is wet (or saturated), what is likely to happen, please? Is it expected that the block will break or, the water will come up between the cracks. I'm currently working on my drive (in the drier periods - not many lately!) and want to avoid the pitfalls. On a previous post (Compaction), I have indicated that I am trying to keep my 'un-compacted' work as dry as I can, by covering in plastic type sheeting as I progress. I'm currently waiting for a dry-ish spell as, LLL and Pablo have indicated I can whacker in so far.
H
Posted: Thu Nov 04, 2010 3:48 pm
by intercityuk
yes good question, according to other posts once you have compacted the blocks it doesn't matter if the bedding sand gets soaking wet which it will if not sealed with kilm sand
So is this correct, if blocks not compacted and bedding sand is wet you cannot compact them and you have to wait until the sand is dry which is not going to happen until summer. But if the blocks are compacted before the sand got wet then it can piss down all day and thats ok, even though the sand is still going to get totally pissed wet through.
Hope you understand the question not sure i do
cheers
Posted: Fri Nov 05, 2010 10:06 am
by Tony McC
If the laying course sand is the right stuff, it should not be saturated for very long. One of the reasons why a coarse, free-draining sand is specified as a laying course material is to ensure that water doesn't hang around within the laying course for any longer than is necessary, because it can cause the sand to "fluidise", which means it starts to act like a liquid, flowing moving and pumping up through the joints.
If a laying course is saturating, then you need to know why, and the two most common reasons are that it's the wrong type of sand or that the sub-base is impermeable and there's nowhere for the water to escape (which is why we don't normally lay over a concrete base).
With a good laying course sand, no matter how heavy the rain, it should drain itself to being just about damp inside an hour. If a laying course has been spread and then it gets soaked, it's best to leave it to drain until it reaches a point when puddling the surface (tapping lightly with the sole of a boot) doesn't bring any water to the surface. For laying course sand that's not been laid, it should be piled-up so that the top part will drain more readily, and it should be covered with a tarpaulin or similar to keep the worst of the weather off it until it's needed.
Posted: Fri Nov 05, 2010 10:42 am
by Aitch
Thanks, Tony.
that's a another potential pitfall avoided. I was hoping someone would 'throw the pearls' last night but, you've just done it as I've been making my way through other areas of the forum.
By the way, have to say, it's really good of you guys to share your professional knowledge with some of us DIY'ers on this fantastic website, who, nonetheless aspire to acheive the best in a project. My normal job is so far removed from the construction game but, in a past life I have shared the craic whilst 'pile driving' on the Runcorn Shopping City project in the late 60's and the now demolished Netherly Farm estate, with Wimpey's and others, during my student days. Great set of guys. ( sorry to sound like a T**t but, truly great memories of some really good times with, many down to earth, tell it like it is characters. Great times / memories!)
H.
Posted: Fri Nov 05, 2010 11:03 am
by intercityuk
Thanks very much Tony for putting my mind at rest i can now continue with my drive, what a fantastic, clear and precise answer ! And thanks to Aitch for the question.
cheers
Posted: Mon Jan 24, 2011 6:05 pm
by paddcomp
On this subject of laying blocks during wet weather, I too am halfway through a block paving project. I have a T shaped drive of about 100sqm, which I have been comtemplating renewing for some years.
After reading Tony's advice I thought I'd give it a try, how hard can it be?
So far so good, until the weather struck. First the frost, then the snow and the rain. The drive has multiple slopes and the only horizontal line is where it meets the garage floor.
I used the existing sub base (MOT) as it hasn't moved in 20 odd years. But once the kerbs were in it looks like a swimming pool in the lower corners, and doesn't naturally flow toward the road.
The upper areas dry out well enough to compact and lay blocks. I'm concerned reading your earlier reply that it should drain better via the sub base.
I haven't compacted the wet areas yet as I found by trial and error that you can come close to loosing a whacker plate in 2" of sand when soaked!
Will I be okay letting the grit sand loosely spread out dry then compacting and laying blocks, with the apparent lack of drainage? Or should I investigate now (I know that it's clay underneath, as the whole village is on a river estuary).
Great site and continues to be a much read source of information to most outdoor DIY.
Posted: Mon Jan 24, 2011 8:33 pm
by oioisonnyboy
If the water doesn't drain to the road, where does it drain to? do you have a gully pot or a linear drain anywhere on this driveway?
If the sub base has been down for 20 years, probably very tight and very solid. If the water is just in the lowest corners, probaly easiest to get a couple of tonne bags of type 1, loosen the existing sub base in these damper areas.
If it is very snotty, remove it until you reach sound sub base. top up with new dry type1 and wack well. Do not wack any sub base where there is standing water or if it feels wet to the touch, it will turn to pudden, and you will end up digging it out again.
When wacking the laying sand, no water should come up to the top. The surface should be nice firm and tight, as mentioned earlier proper sharp sand dries out pretty quick.
Posted: Tue Jan 25, 2011 10:13 am
by Tony McC
If this ponding water was left for a period of time, would it drain away to ground, or is it permanently wet?
If it eventually drains, then it's probably OK to pave over it. Bale out as much water as poss before placing the laying course. Dig a sump if necessary to get rid of it, then get it paved over as quick as you can.
As your drive is on a slope, you should be starting at the bottom, where the water is, and working uphill.
Posted: Tue Jan 25, 2011 10:45 pm
by paddcomp
I don't have any gullys or drains, and a soak away would need a large hole due to the clay ground. Due to the shape and angles of the drive water can collect in low areas which are currently formed inside the kerbs.
I think the water will evaporate/drain eventually, it only appeared when I dug up the old drive and the kerbs formed a retaining edge. I haven't had a dry enough period to know how long it takes to drain properly. I suspect a week of continous dry weather would do it.
Ideally I should alter the levels but as I want to keep the old base and kerbs (cost reduction), I bought the CBP from Marshalls Ebay for £750 (96sqm), and needed some additional charcoal for the borders. Current total cost for 100sqm £2K.
The old drive was tarmac so was watertight, but didn't puddle.
Don't know if this is the right place for pictures but here's a link to some I took earlier.
http://s335.photobucket.com/albums/m466/Paddcomp/driveway/