How to Build a Patio - Design and
lay a patio
This is a substantial article - It would probably be
better if you print it out -
you choose your paving for the patio, try to see it
laid somewhere in a real life situation. Don't buy
on the basis of catalogue pictures. The colours are
not always true; catalogue patios are often set up
in a photographic studio, where the lighting will
enhance the texture of the slab.
You will rarely see
a patio picture in a catalogue, without some form of
planting design around the edges. The art director
knows that this enhances the effect of the paving -
learn from this.
There is no need to
stick to one type of paving or surface in the design
- experiment. Pebbles, gravels, bricks and tiles,
can all be incorporated. A contrasting brick edge
can also be effective.
Generally, it is better to choose a
colour that contrasts or compliments, when the patio is laid near to the
house. Do not try to match the colour of the brickwork for instance.
(Dark brickwork - light paving and visa versa). Dark colours are less
reflective and are therefore not so much of problem in terms of `glare'.
Do not underestimate the effect
of glare. Make your patio user-friendly. A darker slab will also feel
much warmer (or hotter) than a lighter slab, and will retain - and
radiate heat well into the evening after the sun has disappeared.
The sizes of paving slabs
are usually given in `nominal' measurements. Bear this in
mind when you first design your patio area. The
measurement includes the pointing which you are going to
have to do - usually a 10mm allowance. This is important
to bear in mind if you decide for some reason to butt your
slabs together instead of pointing them. A 600x600mm slab
will probably be only 590x590mm in real life. If you make
provision for a 12 slab run of butted slabs, you will end
up 120mm short (5 inches). This can be quite upsetting.
Alternatively, if your
jointing/pointing is nearer to 20mm wide, then you can end
up 120mm (5 inches) over your estimate on a twelve slab
run. (Even more upsetting!)
With some of the
riven/york finish slabs, it is virtually impossible to
provide the 8-10mm joints advocated in some catalogues
when laying the slabs - especially if using a combination
of sizes for a random rectangular effect, unless you
simply dribble sand down the gaps. (This is quite
acceptable in some instances). It is a good idea to lay
some of your slabs out on some level ground, to get the
feel of them and assess joint width.
If using a random
rectangular pattern design to lay your patio, then make
sure that you choose paving which work within the pattern.
The relevant sizes will have to be in multiples of the
smallest dimension. For instance, 300x300mm, 600x300mm,
and 600x600mm will form a `random rectangular' bond, but
you will not be able to include 450x450mm. To use the
450x450mm slabs within a pattern you will have to
incorporate them with 225x225mm, 225x450 and possibly
Make a laying plan, or
get a ready-made 'pattern-sheet' from your supplier which
will have various random patterns printed out. I find that
for laying 'three-size' patterns, a ratio of say 30:60:35
of 600x600mm : 600x300mm : 300x300 respectively, works out
fine. `Random' it may look, but plan it to look that way!
If you have to cut slabs
at the edges or whatever, then a diamond disc blade is
best - wear ear defenders and goggles. If you just have a
few cuts, then you can get away with a `stone' cutting
disc at £2.oo - 3.oo each. The diamond disc is around
£100.oo, but will last 40-50 times longer than a `stone'
disc. You can hire them, but they are expensive. Charged
at up to £60.oo per millimetre used - a big rip off!
How to build your
Patio - Laying the paving
So, you have decided upon
the design elements. let's get down to the easy bit -
laying the patio!
The two most common
construction faults which spoil patios, are uneven
surfaces, and poor foundation preparation, which can
result in the patio `breaking up' and sinking in sections.
get this right before you start to lay your patio.
If the area where the
patio is to go has a hard well-compacted soil base, then
huge quantities of hardcore are not necessary. This type
of compacted soil base is found in areas that have been
well walked upon over years, or have been subject to
several passes by heavy machinery. If you can dig your
heel into the surface, then it will need bolstering up
with a layer of MOT type 1 sub-base, compacted into the
surface with a hired plate compactor.
Where the area has been
used as a flower bed, or otherwise cultivated during the
last few years, then it will certainly need to be
prepared. A compacted base of hardcore rubble, followed by
a blinding of gravel or MOT type 1 sub-base material is
then laid and compacted. This can be as little as 50mm
`Made-up' ground, (where
soil has been deposited to raise levels) will certainly
need a well prepared foundation after extensive compacting
of the soil base. It would be wise to leave the area to
settle before attempting to construct a patio. Regular
drenches of water will accelerate the settling process.
Foundation bases are best
prepared from compacted rubble and or MOT type 1 sub-base
material. (Scalpings). Compact your base with a hired
plate compactor. The finished base should be even without
any voids between the lumps of rubble/hardcore.
The first thing to sort
out before you lay your patio, is the accurate marking out
of the patio shape from your design. If you want a
sweeping curve, experiment with a hosepipe laid upon the
ground until you get the shape you require, then put
temporary canes or pegs along the curve.
If the area - or part of
it - is to be based upon a right-angle, then set out by
using the 3-4-5 method. Do take time to ensure that you
get this set right.
DPC - Damp Proof Course
Decide where the finished
level of the patio is to be in relation to surrounding
ground levels and damp-proof course on buildings. It
should be at least 150mm below the DPC. In deciding the
finished levels, you will have to allow for a `fall'
across the patio, to allow rainwater to run off. (Where is
it going to go?) You may need a drainage channel for the
surface water to run into in some circumstances. (In
theory, water will actually run off a perfectly level
surface, but your laying technique will have to be spot on
to ensure no puddling. The patio will also have to be
above the surrounding ground levels.)
A normal `fall' of around 50mm over 2.4 metres is quite
adequate. (This will give you a 2inch fall over the length
of an 8 foot long `straightedge' in old money, and will
not have people toppling off chairs.)
If the patio is
going next to the house, then the fall must be away from
the house. If it is absolutely impossible to fall away
from the house, then surface water must be intercepted by
a suitable drainage channel with adequate collection
pit/soak-away. This is best incorporated when you lay your
You should start laying
your paving from a straight base line and work from that.
Do not try to work from two fronts when using regular
patterned slabs, for a slight discrepancy in your
right-angle will be magnified as you progress and you
could end up with widening or narrowing joints .
It is possible to lay
some slabs onto a sand/cement mortar mix that has simply
been screeded, but more often than not it will be better
to lay each slab individually from a `trowelled bed'.
Commonly, five dabs of mortar are put down - one for each
corner and one in the middle. Alternatively, a shovel of
mortar can be dumped where the slab is to be laid, and
then trowelled out.
The mortar mix should not
be too wet. Unlike bricks, paving stones are made from
concrete; which does not soak up moisture. A wet mix will
have your paving slabs `floating' and as you tap one down,
an adjoining one will rise - leaving you with an uneven
surface. The mortar will need to be firm enough to allow
the slabs to be bedded down firmly into place.
Coarse sharp sand is
normally used for the mix in preference to the softer
`building sand'. I often use a 50/50 mixture of coarse and
building sand. It works out at half bag of each in the
mix, with one and a half shovels of cement. You will need
to determine the volumes of the bags of aggregate in your
own area. The coarse sand gives the strength, whilst the
building sand makes the mortar just a little more pliable
- easier to tap the slab down into position. This mix also
seems to adhere to the slabs better than a sharp sand mix.
A bedding mix of 5 aggregate (sand) to 1 of cement is
usually sufficient. Perhaps a slightly stronger mix of 4
to 1 in less stable soils.
If the slab you are
positioning does not want to `sit down', take it back up,
remove the mortar mix from slab and base and start again.
Likewise, if the slab is too eager to `sit down' do not be
tempted to raise it up and ram mortar under the edge. Take
it up; start again. Check in all directions with your
For tapping the slab into
position, I tend to use a pickaxe. A 1 metre length of
100x100mm (4x4inch) fence post will also act as a good
punner - especially when it has been used a few times to
soften the end.
(If the slab is just a
little stubborn, try tapping your punner - on top - from
side to side. This slight sideways movement can often drop
your slab a further centimetre.)
If the slabs have a flat
un-patterned surface then the levelling process - using a
straight edge - is reasonably basic. However, remember to
set the slab to levels from two ways. With artificial
stone patterning, laying true to levels is usually a
little more difficult. There can be as much a cm
difference in levels from centre to edge one way or the
other. This is where the ` eye' comes into its own. A good
practice in the case of uneven slabs, is to run the
straight-edge along the edge, rather than across the
middle. Alternatively, use the high spots of the slab as
your level line, and ignore any dips towards the edges.
This gives it a more realistic effect anyway. It may be
better to increase the fall with this type of slab to
prevent any rainwater lingering. Say 75mm (3 inches) over
2.4 metres (8 feet).
The mixture for jointing
your slabs will depend to a certain extent on the type of
paving that you use. If you use a `pressed' slab - these
are normally cheaper and have very square edges, with both
faces of the slab very similar in appearance - then a
rather dry pointing mix is best. It is more difficult to
remove cement mortar stains from this type of paving. For
the moulded slabs - a smoother finish, bevelled edges with
the reverse different to the face side - then a normal
mortar mix will be in order. It is much easier to remove
mortar stains from the surface of this type of slab.
The mixture should be of
the ratio 1 part (by volume) cement to 3.5 - 4 parts
building sand. Coarse sharp sand can also be used where
preferable, and gives a more durable joint in areas of
The jointing/pointing of
the paving is very important to the success and longevity
of your work. It is not simply a cosmetic exercise. Make
sure that the pointing mortar goes right down into the
joints. It is far better to have a slightly messy slab,
which can be easily cleaned, but with a total bond between
joint and mortar base.
Use a complementary or
contrasting colour pigment in the mortar. Brown, black or
buff are usually all right - not red. All coloured mixes
tone down considerably upon drying. Experiment if unsure.
The newly laid and
pointed patio, should be allowed time to `cure' before
using. This should be for at least three days in the
spring/summer months. Cover with a polythene sheet and
sprinkle with water during this time if necessary. Do not
allow to dry out too quickly.
Joints can either be
recessed by raking out partially dry mortar with a trowel
or other metal `scraper', or they can be trowelled to a
range of shapes. The final cleaning of `grogs' should be
carried out when the mortar is near to dry - anything from
6 to 48 hours depending upon the temperature. I usually
carry this out on the following day.
Does your patio resemble the original design?
Let me know when the grand opening is to be.....
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By David Hughes -