Laying and building a fall on concrete (complex!)

[James27]

Hi
I'm new to this forum and flag laying so you'll have to forgive me if i seem a bit amateur! Basically i have dug down about 200mm to the subgrade. However i found 2 long strips of concrete about 100mm down. I have a 2x4m rectangle of 8sqm patio area.
There is a strip of concrete running down the length about 3m and then it stops and goes across the width by about 1 and a half metres. I am laying a sub base of dtp1 and bringing it up to the level of the concrete figuring i could combine the 2 bases, the dtp1 and the concrete and then put my laying course on top of the level of concrete and dtp1.
My problem is that is it ok to combine a flexible subbase of dtp1 and inflexible subbase of concrete, will there be settlement issues with the flags? And also i plan to build a fall for drainage into the area, i cant build the fall on to the concrete as it is flat, do i put dtp1 on to the concrete and bring the whole surface level up to then make a slope or do i make a slope with the laying course (i have heard this is a bad idea). Can anyone help? Sorry for the long post!

[msh paving]

Hi
I'm new to this forum and flag laying so you'll have to forgive me if i seem a bit amateur! Basically i have dug down about 200mm to the subgrade. However i found 2 long strips of concrete about 100mm down. I have a 2x4m rectangle of 8sqm patio area.
There is a strip of concrete running down the length about 3m and then it stops and goes across the width by about 1 and a half metres. I am laying a sub base of dtp1 and bringing it up to the level of the concrete figuring i could combine the 2 bases, the dtp1 and the concrete and then put my laying course on top of the level of concrete and dtp1.
My problem is that is it ok to combine a flexible subbase of dtp1 and inflexible subbase of concrete, will there be settlement issues with the flags? And also i plan to build a fall for drainage into the area, i cant build the fall on to the concrete as it is flat, do i put dtp1 on to the concrete and bring the whole surface level up to then make a slope or do i make a slope with the laying course (i have heard this is a bad idea). Can anyone help? Sorry for the long post!

Leave the concrete in ,won't do any harm probilly a old wall footing or covering a shallow drain pipe run.Form the slope using the type1 ,on that area the slope is not a great amount so you will get over the concrete but dont worry if the concrete shows in the laying course 25mm or so,Lay the slabs on a wet mix as discribed in the main site

www.pavingexpert.com/layflag1.htm

MSH

[James27]

Hi MSH thanks for the reply its great to have a forum like this to get some valuable advice!
Here is my site for the new patio, If i understand you correctly i can put a transverse/horizontal slope using the type 1 so the bottom of the slope is the concrete (draining into the grass)? And then lay the bedding mix on to that? Should i use a 10:1 semi dry mix or does it have to be a wet mix? To make the horizontal slope i will have to put some type1 on the other bit of the concrete? Will it compact ok? Sorry about all the questions!

[msh paving]

sounds good to me MSH

[James27]

ok thanks MSH i will do that then, fingers crossed i will be enjoyin the new patio soon!