levelling with a line

[tcb1973]

hi,

hoping someone can break down the process of using pegs and string to create levels for laying a patio.

I understand i need to take account of the sub level, bedding material and the slabs. And that I need a fall so the water will drain (this is at the bottom of the garden, not by the house).

I am confused as to how to use the line? I mark out my area (square in this case) and put a peg in each corner. Then i attach the line and make level using a line level. How does that help me when digging down and to know how far i have gone and if it is level?

I obviously am missing something and could really do with an idiots guide, i.e. step-by-well-explained-step

Hope someone has the time?

cheers in advance

sam

 

[r896neo]

Here's how i do it. First i'll assume for describing the process that you have a simple square patio running off the back wall of the house.

At the house/ higher side mark on the wall where you want the top of the finished paving to be height wise and then transfer this height onto the 2 corner pegs at that side. Then with a line and line level or a long straight edge transfer this mark minus your desired fall (eg 50mm) to the opposite two corner posts. of course if you need to fall it in two directions then you'll need to take this into account. (This bit it sounds like your on top of already)

Add up the depth of your flag say for simplicity its 50mm then the depth of the bedding say another 50mm then the depth of your sub-base say another 100mm now dig out along the string lines to 200mm deep. Then dig out the rest with the aid of a spirit level knowing that as long as the spirit level is level then you are at the same depth.

The sub-base should be dig out with a fall in it rather than putting a fall in with a deeper base at one side.



At this point there are two options, for block paving I lay some sub base and compact it along the line of the two side string lines (the ones perpendicular to the house) Then i replace them with straight edges/ screeds at the desired height of finished surface minus paving thickness. Then all you need to do is fill in the middle using a string line or straight edge and a tape measure between the two screeds to keep you right. i.e. you want the sub-base to finish 100mm low of the screeds. (50 for sand 50 for paver) Then plate all that down and throw the sand down and plate over the lot, and simply use the screeds for screeding.


For anything non calibrated like sandstone i find it easiest to replace your string lines at the two sides perpendicular to the house with a straight edge of some sort also add one in the middle if your patio is very wide. This then means that you have a finished surface height at each side but they also have the necessary fall included in them. Now Prepare you sub-base in the same way as above with straight edge and tape for the dip. Once done with that you can start laying the flags by again running a string line between the two 'set' straightedges at each side keeping them level with the line and knowing that means they have the desired fall and the whole lot is flat. It can all be done with string lines but i find it easier this way as you can nudge a line out of level and not realise until it's too late.

Wow that was long.

 

[tcb1973]

ok - if I'm not going from the side of a house and I want the top of the paving to be at the current ground height, how do I use the peg/string?

In your example, is the top of the peg the required height or is where the string is on the peg the required height? Also to include the fall - do I get the string level on both the pegs, and then on the lower side measure my fall on the peg (say 50mm) and move the string down that much?


then when the line is set (with the fall) I use a tape measure and dig the required depth(say 200m) all along the two side with the fall. Then I dig across the area using a spirit level to ensure I'm digging down the correct amount?

then as i add sub base - i use the tape measure against the line to make sure i add 100m i.e I add until I am 100m below the line. measuring against the line will mean i retain the fall?

sorry if these questions are dumb - just wanna be clear before I start. thanks for your time and help though - much appreciated.
[[/i]

 

[r896neo]

1. If you just want it flush with the current ground level then bang in your peg and mark it at the height of the grass.

2.The top of the peg is not used for heights, it's easiest to just make a mark or notch on it and use that. Yes to set the falls get the string level across both pegs first and then measure your 50mm down and mark/notch there.

3. Correct

4. Right again.