Building a wall on a patio

[Bert Coules]

This is almost certainly one of those questions where the answer depends on
details I can't yet provide, but anyway...

I want to lay a patio some eight feet deep using (or rather re-using) 400 x
400 x 28mm slabs. At a later date, I want to erect a two-foot high wall,
probably of single-skin brick, along part of the long edge of the patio.

How feasible would it be to build the wall actually onto the patio itself?
That's to say not digging out and laying any separate foundation?

Many thanks.

[Harry Bloomfield]

After serious thinking Bert Coules wrote :

It wouldn't, it would need a foundation of some sort or the weight
would cause it to sink.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

[Fredxxx]

Of course that could be under the offending slabs.

[Bert Coules]

Thanks for the replies, and for confirming my suspicions. So the sensible
thing to do would be to lay the foundation for the wall at the same time as
creating the patio, even though the wall would be a later addition)?

[stuart noble]

I've just done a similar (8ft x 8ft) thing, but I thought the bricks
would have looked odd stuck on the slabs. No big deal to dig out a small
trench alongside the patio. I had a bit of hardcore to get rid of anyway.

[ARW]

"Bert Coules" <ma...@bertcoules.co.uk> wrote in message
news:zpSdnf2r6dLLz-_O...@brightview.co.uk...

> Thanks for the replies, and for confirming my suspicions. So the sensible
> thing to do would be to lay the foundation for the wall at the same time
> as creating the patio, even though the wall would be a later addition)?
>

Yes. And the single skin wall might need supports at the ends.

--
Adam

[harryagain]

"Bert Coules" <ma...@bertcoules.co.uk> wrote in message

news:Hvednaq19Lo43u_O...@brightview.co.uk...

Zero feasibility.

[Bert Coules]

Stuart Noble wrote:

> No big deal to dig out a small trench alongside the patio.

That does seem to be the way to go, so thanks for the confirmation. Did you
extend the trench actually under the patio's edge, so as to have a
foundation wide than the wall?

[Bert Coules]

"harryagain" wrote:

> Zero feasibility.

Succinctly put. Thank you.

[Bert Coules]

"ARW" wrote:

> Yes. And the single skin wall might need supports at the ends.

I was assuming so, and perhaps elsewhere along its length as well.

[The Natural Philosopher]

I'd go down about a foot, build the wall with metal ties to make sure it
didnt split and then lay the slabs later.

--
Ineptocracy

(in-ep-toc’-ra-cy) – a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

[The Natural Philosopher]

yes. OR use stuff like rebar IN the wall. Remember a atrip foundation is
simply to stop local stresses cracking the wall or it rising or sinking.

If all you care about is not cracking, reinforce the wall with steel.


If you do a simple stretcher bond double wall capped wit a soldier
course there's room to use steel between the courses and in vertical and
horizontal directions, and some ties will hold the courses together as well.

[Bert Coules]

The Natural Philosopher wrote:

> I'd go down about a foot, build the wall with metal ties to make sure it

> didn't split and then lay the slabs later.

Thanks. It's sound advice but unfortunately, for reasons far too boring to
go into, the patio has to come first.

[Phil L]

It's never a good idea to build on top of slabs, regardless of what you may
put under them.

Is there any reason why you can't stop the patio at 7ft 6 and then next year
(or whenever) hand dig a small trench 5 inches by 5 inches and lay a bit of
dryish concrete and build the dwarf wall on that?

If the wall isn't to cover the entire length, simply fill to the surface of
the slabs in this part and smooth the concrete

[meow...@care2.com]

On Tuesday, May 13, 2014 7:16:01 PM UTC+1, The Natural Philosopher wrote:
> On 13/05/14 18:11, Bert Coules wrote:
> > Thanks for the replies, and for confirming my suspicions. So the
> > sensible thing to do would be to lay the foundation for the wall at the
> > same time as creating the patio, even though the wall would be a later
> > addition)?

> yes. OR use stuff like rebar IN the wall. Remember a atrip foundation is
> simply to stop local stresses cracking the wall or it rising or sinking.
> If all you care about is not cracking, reinforce the wall with steel.
> If you do a simple stretcher bond double wall capped wit a soldier
> course there's room to use steel between the courses and in vertical and
> horizontal directions, and some ties will hold the courses together as well.

Steel in a wall introduces a likely failure mode. Rope in each course is good enough if you wanted some reinforcement. With a 2' high wall I certainly wouldnt use this as an excuse to skimp on the footings - thats only practical for tiny walls.


NT

[Bert Coules]

Phil L wrote:

> Is there any reason why you can't stop the patio at 7ft 6 and then next
> year (or whenever) hand dig a small trench 5 inches by 5 inches and lay a
> bit of dryish concrete and build the dwarf wall on that?

None whatsoever and thanks for the suggestion. I was just exploring the
various possibilities. The overwhelming agreement is clearly that building
anything as heavy as even a not-very-tall wall onto paving slabs is not a
good idea and I'm entirely happy to go along with that.

My initial thought was simply that the difference between a solid concrete
foundation slab laid onto earth and a row of solid paving slabs laid onto
sand might be small enough for the latter to act as a reasonable substitute
for the former.

[John Rumm]

Yup. You won't need a huge foundation for a 2' wall. If you know where
its going to be when doing the patio, stick in a 8" - 12" deep concrete
haunch along that side, and bed those slabs on mortar even if the rest
are laid on dry mix or just sharp sand.


--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

[The Natural Philosopher]

On 13/05/14 22:29, meow...@care2.com wrote:
> Steel in a wall introduces a likely failure mode.

I think you had better tell that to the shard and onion people

They will be very interested to know that.

[stuart noble]

No. I regarded the patio base as sufficient on that side, and there's
probably a brick width on the other side. What the hell, it's only a
small retaining wall, and I'd rather grow things than fill the space
with footings. If it fails, I'll stick it all back together :-)

[Tim Lamb]

In message <WY2dnfqeJ78AB-_O...@brightview.co.uk>, John
Rumm <see.my.s...@nowhere.null> writes

>On 13/05/2014 18:11, Bert Coules wrote:
>> Thanks for the replies, and for confirming my suspicions. So the
>> sensible thing to do would be to lay the foundation for the wall at the
>> same time as creating the patio, even though the wall would be a later
>> addition)?
>
>Yup. You won't need a huge foundation for a 2' wall. If you know where
>its going to be when doing the patio, stick in a 8" - 12" deep concrete
>haunch along that side, and bed those slabs on mortar even if the rest
>are laid on dry mix or just sharp sand.

In advance of a daughter's wedding, I did some hurried patio laying on
dry mix over compacted type 1 with a dwarf wall (2 stretchers + soldier
course) to retain a raised border.

Rather than cut each slab to suit the curves of the border, I laid the
wall on top of the slabs. However, before bringing the soil back to the
wall, I buttressed the wall from below slab level and up to the soldiers
with a stiff mix concrete. Still looks fine.
--
Tim Lamb

[Dave Liquorice]

On Tue, 13 May 2014 17:49:19 +0100, Harry Bloomfield wrote:

>> I want to lay a patio some eight feet deep using (or rather
re-using)
>> 400 x 400 x 28mm slabs. At a later date, I want to erect a
two-foot
>> high wall, probably of single-skin brick, along part of the long
edge
>> of the patio.
>

> It wouldn't, it would need a foundation of some sort or the weight
> would cause it to sink.

I can't see a 2' high single skin wall laid down the center line of
400 mm sq well bedded slabs sinking into the ground. Probably a
better footing than a narroe small trench and a few inches of
concrete, the load will be spread for a start.

TBH I'm more worried about the later mentions of "retaining wall".
Single skin 2' high and 8' long high will almost blow over. B-)
It'll need some vertical reinforcing of some sort.

--
Cheers
Dave.

[Brian Gaff]

Erm, would not the weight just tip the paving up and dump the wall outwards,
especially if anyone tried to sit on it?
Brian

--
From the Sofa of Brian Gaff Reply address is active

"Bert Coules" <ma...@bertcoules.co.uk> wrote in message
news:Hvednaq19Lo43u_O...@brightview.co.uk...

[Brian Gaff]

Far better though to build the all first and use it as an edge for the patio
to stop it moving outwards on that edge

Brian

--
From the Sofa of Brian Gaff Reply address is active

"Fredxxx" <fre...@nospam.com> wrote in message
news:lktjgv$u9c$1...@dont-email.me...

[Bert Coules]

Thanks to everyone for the new replies and the advice, pro and con.

[meow...@care2.com]

On Wednesday, May 14, 2014 4:46:38 AM UTC+1, The Natural Philosopher wrote:
> On 13/05/14 22:29, meow...@care2.com wrote:

> > Steel in a wall introduces a likely failure mode.

> I think you had better tell that to the shard and onion people
> They will be very interested to know that.

I was of course referring to rebar in a domestic diyed 4" brick wall, a very different proposition to the design of the onion & shard.


NT

[Andrew Gabriel]

In article <7a129dd3-f012-4dae...@googlegroups.com>,

You can buy stainless steel rebar.

(You can also buy galvanised, but that does eventually fail in wet mortar,
which is why wall ties are now stainless steel.)

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

[Andrew Gabriel]

In article <nyyfbegfubjuvyypb...@srv1.howhill.co.uk>,

"Dave Liquorice" <allsortsn...@howhill.com> writes:
> On Tue, 13 May 2014 17:49:19 +0100, Harry Bloomfield wrote:
>
>>> I want to lay a patio some eight feet deep using (or rather
> re-using)
>>> 400 x 400 x 28mm slabs. At a later date, I want to erect a
> two-foot
>>> high wall, probably of single-skin brick, along part of the long
> edge
>>> of the patio.
>>
>> It wouldn't, it would need a foundation of some sort or the weight
>> would cause it to sink.
>
> I can't see a 2' high single skin wall laid down the center line of
> 400 mm sq well bedded slabs sinking into the ground. Probably a
> better footing than a narroe small trench and a few inches of
> concrete, the load will be spread for a start.

Paving slabs will easily snap if you put a weight like that on
them - the foundations under the weight would only need to settle
a millimeter or two to generate a stress across the slab.
Alternatively, any settling would cause the slab to sink on the
heavier side, possibly lifting the other side, and the wall to
tilt.

> TBH I'm more worried about the later mentions of "retaining wall".
> Single skin 2' high and 8' long high will almost blow over. B-)
> It'll need some vertical reinforcing of some sort.

Can't see the mention of retaining wall, but a half brick wall
won't retain anything. Some were built in an area I walk past,
and they are a poured concrete wall with embedded steel mesh,
and then a brick wall decorative face was added at the end,
tied into the concrete face.

[John Rumm]

However as has been said, you can still stick the required footing under
the patio.

[Bert Coules]

John Rumm wrote:

> However as has been said, you can still stick the required footing under
> the patio.

Belated thanks for that: it is clearly the sensible approach.

[John Rumm]

On 13/05/2014 19:01, Bert Coules wrote:

That's harry - to the point, and wrong...

[meow...@care2.com]

On Wednesday, May 14, 2014 10:27:38 PM UTC+1, Andrew Gabriel wrote:
> In article <7a129dd3-f012-4dae...@googlegroups.com>,
> meow...@care2.com writes:
> > On Wednesday, May 14, 2014 4:46:38 AM UTC+1, The Natural Philosopher wrote:
> >> On 13/05/14 22:29, meow...@care2.com wrote:

> >> > Steel in a wall introduces a likely failure mode.

> >> I think you had better tell that to the shard and onion people
> >> They will be very interested to know that.

> > I was of course referring to rebar in a domestic diyed 4" brick wall, a very different proposition to the design of the onion & shard.

> You can buy stainless steel rebar.
> (You can also buy galvanised, but that does eventually fail in wet mortar,
> which is why wall ties are now stainless steel.)

You can, but nearly all folk seem to insist on using galv. (IME galv fails in dry locations too.)


NT