Patio sub base

Patio flagstones (slabs), concrete flags, stone flags including yorkstone and imported flagstones.
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Ematt
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Joined: Fri Apr 04, 2014 1:22 pm
Location: United Kingdom

Post: # 96874Post Ematt

Hi, I`ve dug up my old 23 square metre patio and prepared the ground to put in a 100 m sub base which i`ll wack down. The base i have dug out though is very sandy in parts and now boggy in parts after constant rain.

Is it ok to put my sub base over sand and should i wait for it to completely dry out?

seanandruby
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Post: # 96906Post seanandruby

Isn't the sand from the old base? See how deep it goes, dig it out and any soft spots, fill soft spots and then start the formation
sean

Ematt
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Joined: Fri Apr 04, 2014 1:22 pm
Location: United Kingdom

Post: # 96908Post Ematt

It seems too deep to be from the old base as I,ve dug out 6 inches and there is still another 6 inches of sand in parts, goes as deep as the pipes. If I wack the sand down can I then wack down the hard core?

Mikey_C
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Joined: Mon Oct 30, 2006 8:24 pm
Location: Bournemouth, Dorset

Post: # 96914Post Mikey_C

Ematt wrote:"as deep as the pipes"
what pipes? are they drainage pipes, is the sand pipe bedding?
If it is drainage pipes you may want to explore details on the site about when to encase them in concrete?

seanandruby
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Post: # 96916Post seanandruby

Maybe sand for sevices so be careful, could be gas or leccie. Are there tiles, or electric/gas warning tape in the trench?
sean

Tony McC
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Post: # 96930Post Tony McC

Once you've resolved the issue with the mystery pipes, you could use a geo-textile (NOT a landscape fabric) to act as a separation membrane between sand and the overlying sub-base.
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Ematt
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Joined: Fri Apr 04, 2014 1:22 pm
Location: United Kingdom

Post: # 96955Post Ematt

The pipe runs from outside the kitchen to a small manhole (inspection ?) about three feet away...can't see anything else but the pipe. Is it a case of putting plenty of the sand back around the pipe and hardcore on top?

Tony McC
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Post: # 97001Post Tony McC

Not "plenty of sand", just 60-100mm or so to act as a cushion. If you put too much, it moves and the sub-base descends into it which can cause settlement.
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Ematt
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Location: United Kingdom

Post: # 97028Post Ematt

Cheers chaps, much appreciate the advice.

Ematt
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Joined: Fri Apr 04, 2014 1:22 pm
Location: United Kingdom

Post: # 97086Post Ematt

Oh and just one more question, is 4 sand to 1 cement for the full mortar bed ok? Seems to be a lot of conflicting advice on this subject online.

Mikey_C
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Location: Bournemouth, Dorset

Post: # 97106Post Mikey_C

what slabs/flags/stone are you laying?

Tony McC
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Post: # 97138Post Tony McC

More than adequate. I usually suggest 10:1 for patio work
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Ematt
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Location: United Kingdom

Post: # 97160Post Ematt

Will be using concrete riven slabs in three different sizes, with a 2 inch fall over 12 feet.

Ematt
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Joined: Fri Apr 04, 2014 1:22 pm
Location: United Kingdom

Post: # 97397Post Ematt

Hello again, i`ve got all my slabs down now a mix of 600x600, 450x450 and 300x300 and i have noticed a few of the 300x300 have not bonded with the mortar and one of them slightly rocks. Whats the best course of action to remedy this? Will this be taken care of when i point up the joints in a couple of days? Also what is the best mortar mix for pointing up? our slabs are buff so i want to keep the joint mortar light in colour so i will need to add a dye i presume.

many thanks for the help so far.

Tony McC
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Post: # 97572Post Tony McC

Loose flags need to be lifted and re-laid. Never rely on pointing to rectify rocking flags: it will fail, maybe not next week, but at some point, it *will* fail.

If you use a pale sand (silver sand, perhaps) you will get a pale mortar without the need to rely on dyes which fade.
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