OK, wondering if the practical contributors on here can help me with some calculations for laying slabs.
Basically, friend had a slabbed driveway which was supported at the edge by a brick wall, the other side of the wall being lawn. Needs to extend the driveway by two slabs for pedestrian / wheelie bin use (not for taking the weight of a car)
Here are some pictures of what I am talking about
s1112.photobucket.com/user/Bobbyg69/library/Driveway
So wall is now knocked down and taken down to a level that is below the level of the slabs. Looking to add in an extra 2 of 60x60 slabs (not the 90x60 that are on existing driveway). So this will mean cutting back the grass a bit. The height at the top of the driveway is 28cm from top of current slab to soil level.
What I am proposing to do is to cut slabs to use as the side support to hold the new slabs up between the slabs and the lawn. Cut these and lay them in with some concrete support to hold them in situ.
So I will then have a void that is currently 30cm at the top of the slope and 0cm at the bottom. The base is currently soil although you can see some of the bricks etc have been tumbled in. I therefore need to put in enough foundation to support these slabs. So what is the best way to do it?
The order I am thinking of is
a. Cut some spare slabs to reflect the slope (assume it is not possible / easy to cut slabs in a vertical position?), put these in with concrete found and leave to solidify,these then form the wall between the path and the grass.
b. Rake out the loose soil and then a layer of hard core whacked down to form a base.
c. More hard core with the brick ends etc to fill it out and then whacked down again
d. then level with type 1 ???? and then sand for laying the slabs (what type of sand?)
What quantities of each should I be looking at?
Assuming that I take another 10cm of soil away, then I am looking at a drop of 40cm at the top and about 10cm at the bottom. There will be 2 rows of 9 slabs so 60cm plus gaps wide..
It is at this point I have got onto calculating areas of triangles on the back of my hand so am I on the right track so far??
|
>> a. Cut some spare slabs to reflect the slope (assume it is not possible /
>> easy to cut slabs in a vertical position?), put these in with concrete found and
>> leave to solidify,these then form the wall between the path and the grass.
Clearly you have never cut slabs, I assume you have an angle grinder? Trust me - dump this idea and buy proper kerbing/edging stones.
I dont see why you have got into triangles. Its simple a matter of depth of base (constant along the entire run by width of drive extension. Sharp sand on top of crushed hardcore (scalpings), lay slabs, and then brush a dry mortar mix and then water with a hose set on fine spray.
Edit, and why use a different size slab? its going to look silly
Last edited by: Zero on Tue 1 Oct 13 at 11:30
|
edit,
Didnt look at the side view picture properly. Which now convinces me even more that cut slabs wont be strong enough to hold back the depth of hardcore you will be using. you may need to build the side up with concrete foundation, 1 or two courses of brick, and then lay the kerb stones on top of that.
Filling the hole left by the wall is simply trigonometry for depth.
|
Yeah I have cut slabs before, usually just hire a Stihl saw from the local place for the day.
Reason she is using 60x60 slabs is she got them free from a friend and the job is very much as cheap as possible job (thus the reason I have been dragged into it!)
I would have thought the slabs would have held everything in if they were given a good enough concrete foundation? Maybe 30cm of slab above ground level and the 20cm below ground level with concrete either side? My dad has an embankment behind his garage which is held in place with 3x2s concreted in and the embankment is the full 3 foot height?
And then you mentioned trigonometry!!!!
|
|
rule of thumb for retaining wall, heighth of wall must not be more than 5 times its width ( roughly)
|
|
I'm with Zero...........................all of the way..............God, don't some folk make a meal of things. Cheap always works out dear my dear.......
|
Help with slab laying calculations!! - Zero
