Complete novice - elevated patio

[mrrodge]

Hi there,

You have a great website. For a complete novice I now feel I’m becoming quite the expert! I have a bit of a question that I can’t seem to find the answer to on there though.

My project is a tiny patio for a static caravan, approx. 2.5m x 2.0m. I have natural green slate from a random pack and have drawn up on the design and almost ‘sussed’ how I’m going to do it. Unfortunately the patio is to be slightly raised (Approx. 200mm), so I have had to improvise a bit. My procedure so far is as follows:

• Demolish old patio and excavate to approximately 50mm.
• Construct plywood to be used as shoring for the elevation.
• Excavate a small trench (approx. 100mm deep by 300mm wide) around the permiter, against the shoring.
• Pour concrete into the new trench and push up to the shoring, approximately 300mm deep (Giving a 150mm rise) and the full width of the trench. I will use a triangular gradient so that the concrete gets shallower the closer to the edge of the trench and the middle of the patio it gets.
• Allow to cure.
• Fill the middle with 150mm of 50mm crusher run. Allow a slight gradient away from the caravan for drainage.
• Compact using my dad’s whacker plate, multiple passes.
• I now have 50mm left before reaching the top.
• This 50mm is to be filled with bedding material, then the flags painted with an SBR/cement mix before laying onto the bedding and tapping down until level.
• The bare concrete sides are to be cladded using more slate and bedding material/adhesive.
• Jointing/pointing is going to be done with the wet method for VDW840+ as recommended by you.

I’m pretty happy with all of this, except for the following:

• Should I use a weed membrane? Where should I put it? I have some heavy duty stuff that lets water through (I know this’s important) and the site is known for brambles growing through the gaps in the flags beneath the caravans.
• Will my concrete edging be strong enough to keep all the crusher run in the middle?
• Here’s the tricky part. The patio has to take the weight of a set of three brick steps up to the caravan with matching slate for the step surface. I have read on parts of the site that excess weight could cause ‘pumping’ with the crusher run. I don’t fancy having my beautiful patio ruined a week after completion by a set of heavy steps being built on top! The steps are to go very close to the right edge of the patio so I can imagine either the right hand concrete shoring to crack or the middle/left of the patio to rise as the weight is put on the right.

After a long time of planning, I think I’m nearly there. Thanks for putting such a great resource on the internet!

[dig dug dan]

to answer in order
1. no. its not gogin to do a thing. normally under block paving you use a geo-fabric, but under a patio its useless

2. Yes, providing its strength and curing times are ok

3. I have never come across the phonomenon known as "pumping" on a crusher sub base. perhaps others can enlighten us??

hope this helps!

[local patios and driveway]

to answer in order
1. no. its not gogin to do a thing. normally under block paving you use a geo-fabric, but under a patio its useless

2. Yes, providing its strength and curing times are ok

3. I have never come across the phonomenon known as "pumping" on a crusher sub base. perhaps others can enlighten us??

hope this helps!

I always put terram under any base to stop it sinking later. It wont stop the weeds because it wont need to.

[dig dug dan]

I always put terram under any base to stop it sinking later. It wont stop the weeds because it wont need to.

fair comment. When i challenged a brew cabiner on here why he didn't use it on a drive, i was machine gunned down, stamped on , set on fire and my ashes scattered. i daren't do that again!

[mrrodge]

Thanks for the quick replies! I reckon I'll give the membrane a miss. Does my design sound good enough on the whole i.e. are there any other problems with it? How about the weight of the steps? I reckon I'll use some thick ply under the slate steps to bridge the void instead of filling the middle with concrete. Or would this put a point load on the patio? Or am I talking crap?

Cheers.

[dig dug dan]

avoid the ply.It will only rot in time and lead to all kinds of trouble
I think you may be worrying too much about the weight of the steps.
I would suggest that you mark the area where you want the steps to be and concrete a small section to build them on.
If you make the concrete low enough to slab over, that way if you are slightly out with your measurments, you can slab over any concrete that is out of alignment.
everything else you propose looks good to me.
lets hope you post photos on here!

[mrrodge]

avoid the ply.It will only rot in time and lead to all kinds of trouble
I think you may be worrying too much about the weight of the steps.
I would suggest that you mark the area where you want the steps to be and concrete a small section to build them on.
If you make the concrete low enough to slab over, that way if you are slightly out with your measurments, you can slab over any concrete that is out of alignment.
everything else you propose looks good to me.
lets hope you post photos on here!

Ah right I never thought of that... So I would make a concrete 'island' so to speak in the middle of the crusher run, then lay the patio on top as normal (as long as I mark where the concrete is) and build the steps on top?

One more query... The polymeric jointing stuff... Obviously I won't be able to sweep that into the joints on the vertical slate where I've cladded over the concrete shoring... Will it mix into a paste and allow me to apply it manually? I'm guessing the right amount of water is pretty critical as it could run back out, or if it won't work at all I'll have to point the whole lot manually with old fashioned mortar to get a colour match.

Thanks again.

[lutonlagerlout]

hi mrrodge
not really happy with your shutter design
better to do a strip footing and lay 1 course of 215 concrete blocks,into the still green concrete
also for such a small area i would just use leanmix instead of sub base,
sbr is good
polymerics with good ones you may get 3-4 years
personally i would use mortar for pointing
hope this helps
LLL

[local patios and driveway]

Dan, i put some pics up of my work and got the same treatment, it was a slaughter because i had left a tea cup on the window sill!! Havnt put any pics up since, but a better crowd on here now

[lutonlagerlout]

lapd you will note that some only post completed jobs
i like the warts and all approach,but thats just me
but in fairness to everyone I do think we should be hard on each other,

pointless having a big schmooze up,when we could all take on board constructive criticism
cheers LLL

[mrrodge]

hi mrrodge
not really happy with your shutter design
better to do a strip footing and lay 1 course of 215 concrete blocks,into the still green concrete
also for such a small area i would just use leanmix instead of sub base,
sbr is good
polymerics with good ones you may get 3-4 years
personally i would use mortar for pointing
hope this helps
LLL

Hi lutonlagerlout,

How deep should the footing be, and the problem I have with lean mix is that the delivery of concrete is not possible, the site is closed (I can't do it when the site is open, disturbing the peace etc) and there's no water or electricity so a mixer is out of the question and I've calculated that the car will carry 300 litres of water. I was going to buy all materials in bags and make multiple trips to deliver them to the site.

I was aiming at using sub base because my dad has a load on the drive from an old project. Is using a lean mix going to cost me a fortune? Maybe I could get a generator to power the mixer.

Thing is there are lots of people with block paving, patios etc. on the site and they've managed it somehow! The existing patio is the same shape and size but it appears to have been supported with a pile of dirt beneath the flags, which obviously isn't ideal!

So if I were to use lean mix, would I just pour this onto the excavated bit in the middle? Would I need anything like reinforcement or membrane? I take it I just use the SBR and lay my flags straight on the wet lean mix instead of a separate bedding layer? I'd struggle to do this in a day I think, so would I be able to lay the flags the following weekend, with a separate bedding layer?

Seeing as I already have crusher run at my disposal, which is the better construction for bearing the weight of the steps?!

I'll be glad to post photos when it's done

Cheers.

[lutonlagerlout]

very few true closed sites rodge
get some right pain in the rear access sites and hard to get water power etc
but there is always a way
LLL

[henpecked]

fair comment. When i challenged a brew cabiner on here why he didn't use it on a drive, i was machine gunned down, stamped on , set on fire and my ashes scattered. i daren't do that again!

Made me laugh, well thats the BC
All the same, nowt wrong with belt and braces approach and like LDP said, it will help guard against sink-age.

[lutonlagerlout]

rodge you are making life really hard for yourself running about with materials in a car
can the site not be accessed at all in working hours?
LLL ???