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Posted: Wed Oct 20, 2010 11:52 pm
by David 1234
I'm about to lay a mowing strip of granite slabs - 300mm wide and the strip will be 32 linear meters and just want to check my quantities and ask about expansion joints.
I've taken a look at the site and think that a C20 mix would be best at 100mm deep. I've had a look at the calculators and at 31.75 linear meters and 100mm deep I reckon I'll need .96m3 of concrete, which comes to 307KG cement, 605KG sand and 1123KG of gravel. In the real world I reckon this means 2 ton bags of ballast and 12 bags of cement.
Please correct me if I'm wrong.
The longer runs of the mowing strip will be 9m and 7m. Are expansion joints going to be necessary on a moxing strip? It'll make the job more difficult for an amateur like me because I'll have to make sure the slabs are cut at to line up with the expansion joints.
Also, I know that this weather isn't ideal for concrete - but it is only a moxing strip. Should I use an additive?
Thank you all.
Posted: Thu Oct 21, 2010 6:51 am
by seanandruby
no need to go so deep for a mowing strip. Just lay them on a 10/1 sharp sand and cement mix 25 / 40ml deep.
Posted: Thu Oct 21, 2010 10:39 am
by David 1234
Thanks Sean - I thought of more substantial footings as the slabs are 600mm x 300mm so it's almost a path. Also it's all clay around here. It's around zero at night - shall I put anti freeze in the mix?
Posted: Thu Oct 21, 2010 12:12 pm
by Mikey_C
by anti freeze i take it you mean frost protector. this is an accelerant which will cause the mix to go off quicker (which will protect it from frost)
if you are a diy'er (like myself) you will need to remember to mix in smaller batches and work with the mix quickly and efficiently.
to this end i never add it to the mix as i didn't feel confident enough.
I always made sure I started as early in the morning as possible to give it a chance to go off and covered it very well with hessian and old balnkets/curtains. never had any problems.
but one man's "its freezing!! is another man's i'll put me top back on (think Newcastle fans in January watching the team with nothing but a beer belly hanging out.)
Posted: Thu Oct 21, 2010 4:44 pm
by David 1234
yep - here in the South under 10 degrees and it's freezing.
Posted: Thu Oct 21, 2010 5:49 pm
by lutonlagerlout
2 tonne of ballast and 10 cement is ample david
i did my mowing strips same as you 100mm of leanmix under each clay paver and none have moved after 5 years
you can cover with hessian sacking to help avoid frost damage
cheers LLL
Posted: Thu Oct 21, 2010 10:17 pm
by seanandruby
did mine with weak screed mix 40 ml and been down 8 years no movement. Just think 100 ml is over engineering for a mowing strip and a lot of extra muckaway.
Posted: Fri Oct 22, 2010 12:07 am
by lutonlagerlout
depends on the ground really
my garden was a vegetable patch so was 12 inches of topsoil all over
newer houses generally have as little topsoil as they can get away with
cheers
LLL
Posted: Fri Oct 22, 2010 8:59 am
by jonnyboyentire
lutonlagerlout wrote:newer houses generally have as little topsoil as they can get away with
cheers
LLL
aint that the truth 
Posted: Fri Oct 22, 2010 12:44 pm
by David 1234
Thank you LLL & Sean. Notorious for sunsidence around here so I'm playing it safe. Can you tell me where I can get hessian or something similar from please? Do you think I can get away with laying straight on top of the concrete or do I have to wait for it to set and then make up mortar and lay the flags the normal way?
Thank you.
Posted: Fri Oct 22, 2010 1:06 pm
by seanandruby
straight on concrete. Get hessian from Any building supplier.
Posted: Fri Oct 22, 2010 5:59 pm
by David 1234
Thank you Sean. If it looks good I'll stick it on the site. If I make a hash of it I'll quietly disappear.
Posted: Sat Oct 23, 2010 10:02 am
by seanandruby
Post it anyway, everyone can learn from mistakes :;):