Complete novice needs help re. sub-base patio (with pics)

[Egg80]

Hello all,

I really need some advice having never attempted anything like this before.

I am attempting to build a 28m² patio and so far I have:

1. Dug out soil to 150mm
2. Added 5 tonnes of type 1 MOT sub-base

I still need to add another tonne but I'm worried about levelling (with the drop) as the size of the grains are so large (pic 5). Should I order a type 2 MOT instead of a type 1 before compaction?

Also, what's the best way of levelling it? Pegs or stringline? I can't seem to find much guidance for this part.

Thanks in advance.

 

[lonner]

Your level and that straight edge are just the job

But you could,
Treat yourself to a cheap little spirit laser level and use that to see the fall.
You can use a tight string line after you have your level.
Looking at thar base which looks fine btw id want about 75-100 mm fall 20- 25mm per metre roughly.
Depends on you finish product as to fall required..
Block paving will need less than a heavy riven slab ect

That will compact really well so simply blind it with some ballast.

Level for the job or something similar
https://www.ebay.co.uk/itm/Mini-Las...442af6ced2:g:vTEAAOSwq-VbiGFw&redirect=mobile

 

[Egg80]

Thanks, Lonner. I've been procrastinating this for some time because I really am out of my depth but I decided to just go for it! So compactor coming tomorrow and I'll see what happens!

Hopefully, the patio won't be too low (its probably going to be just below the top of the 3rd orange brick) so bit of a step down from the patio doors but at least it's below the damp coarse.

 

[SpecialK]

I'm in a similar situation - My first patio .... no way near as big as yours!
I have just wacker plated mine, in places the stones were large on top so I have added some sharp sand and vibrated it again!
Checked its rough level with a lump of decking on its side.

 

[Egg80]

Ah nice one!

I have 2 tonnes of sharp sand and a whacker plate coming today so will see how it goes. Will post an update later today.

Will you set up string line when you come to lay?

 

[SpecialK]

To make it roughly level I have whacked in wood and levelled the type 1 to just below them.
I'm going to put string lines at 90 degrees on the far sides to lay the pattern to as its just a 2.8m square.

The plan is to lay it on a screed mix and use screeding battons for the final level / fall - Hopefully this will work?!

 

[lonner]

Thanks, Lonner. I've been procrastinating this for some time because I really am out of my depth but I decided to just go for it! So compactor coming tomorrow and I'll see what happens!

Hopefully, the patio won't be too low (its probably going to be just below the top of the 3rd orange brick) so bit of a step down from the patio doors but at least it's below the damp coarse.

2 bricks below damp 150mm is perfect, if you are a bit higher 125 mm say you can use a 150 mm gravel strip at the wall which is a good practice anyway as it helps with soil stability footing wise, especially in heavy clay areas. Like side path is already.

 

[Egg80]

Yeah I'm leaving a 4 inch gap for a gravel strip but I messed up...

The base is still quite uneven and I for got to add the fall. Now my pegs are buried so unsure how to remedy...

 

[SpecialK]

You can either dig the sub base to re level or create the fall with the sand/cement layer? My sand base went from about 20mm to 50mm.

You could create the fall first with a sand layer and compact it with the vibrating plate if it needs to be thick?

 

[lonner]

Just scrat a bit off, mot is so easy to adjust.,compared to limestone

It looks good btw just needs a little bit more work.

Dont forget Your a novice so your finding things out as you go , ive seen far far worse from so called professionals.. And caravan dwellers.


What paving are you going to use?

 

[Egg80]

You can either dig the sub base to re level or create the fall with the sand/cement layer? My sand base went from about 20mm to 50mm.

You could create the fall first with a sand layer and compact it with the vibrating plate if it needs to be thick?

Is this an acceptable method? It would be certainly easier to level sharp sand than the MOT.

Just scrat a bit off, mot is so easy to adjust.,compared to limestone

It looks good btw just needs a little bit more work.

Dont forget Your a novice so your finding things out as you go , ive seen far far worse from so called professionals.. And caravan dwellers.


What paving are you going to use?

Im using concrete riven slabs 30mm thick.

So as my width is 4m, the end of my patio that meets the grass should be 5cm approx lower than the edge by the house? If thats the case Im worried ive really messed up as i cant take out anymore mot from the lower end as i wont have enough subbase depth. Think ill have to order more bulk bags and build up towards the house which is going to be expensive. Hope this makes sense.

 

[Charlie George]

You can't make up a 50mm fall in sand, and you will also go above 150mm below dpc,ballast may be a good compromise as is more workable (suggested by lonner).
how are you bedding flags? if you can scrape 20mm or so from bottom of patio you only need to add 30mm to top section.

 

[Egg80]

You can't make up a 50mm fall in sand, and you will also go above 150mm below dpc,ballast may be a good compromise as is more workable (suggested by lonner).
how are you bedding flags? if you can scrape 20mm or so from bottom of patio you only need to add 30mm to top section.

Hi Charlie, this sounds like a plan! Thanks for your input. Now to calculate how much ballast Im going to need to make up that fall.

 

[Charlie George]

The easiest way to work out your fall is to put screw at finished height at house, then level down to bottom of patio,then put stringline on screw and put line 50mm(if this is your fall) below level mark at bottom and measure down from this,it should be same measurement,repeat across patio and allow for flag thickness and bedding, so if your flags are 30mm and bed 40mm your mot will be 70mm below line. 1 tonne ballast should do if you scrape some mot towards top.

 

[lonner]

Hi Charlie, this sounds like a plan! Thanks for your input. Now to calculate how much ballast Im going to need to make up that fall.

A bulk bag of ballast holds about 9 good barrow loads so work on that, bag usually weighs about. 0.9 of a ton
You might only need one or 2 max.

If your screeding the slab bed you can still get your screed pole set if the ballast is a bit high.
With stone its a bugger.

Ps, you only need 25-35mm of bed for them slabs