Okay as promised planning 101.
The first question is whether said play structure is development or not. How you assess this is based on the three test mentioned above size, permenance, and attachement to the ground. There are various Inspectors decisions that cover this concept and as as is the case for a lot of planning there is no straight answer. When I discuss this concept with owners I use hte example of tents. My son has a pop up tent, that literally takes 5 seconds to zip out throw on the ground and it pops up, he plays in it all day and then at the end of the one sunny summer day we have it gets packed away. This tent is without doubt not development based on its size, permenance and attachment to the ground. No let us say I go to a large hotel with lots of surrounding land. They have erected a large tent, or marquee that is the size of a football pitch, and bolted to the ground and took 10 men all day to erect. When talk to the owner he states that he has erected it to allow the hotel to host large wedddings, when questioned he states that it will be in place indefinetly. This almost certianly development based on its size, permenance and attachement to the ground.
So whether the childrens play structure you want to build needs permission will depend on its size, permenance and attachement to the ground.
If it is not development you don't need permission if it is development you need permission. That permission can either be deemed or expressly granted.
The Town and Country Planning (General Permitted Development) (England) Order 2015 (as amended) [henceforth GPDO] grants permssion for a variety of operational development (things you build) and uses of land.
Class E,
Part 1, SChedule 2 of the GPDO allow, subject to the limitations and conditions, permission for buildings in the curtilage (another complicated subject but for now simply consider it a common garden) of a dwellinghouse.
For your convenience I have copied the text below (excuse the formatting) relating to outbuildings:
Class E – buildings etc incidental to the enjoyment of a dwellinghouse
Permitted development
E. The provision within the curtilage of the dwellinghouse of—
(a)
any building or enclosure, swimming or other pool required for a purpose incidental to the enjoyment of the dwellinghouse as such, or the maintenance, improvement or other alteration of such a building or enclosure; or
.
(b)
a container used for domestic heating purposes for the storage of oil or liquid petroleum gas.
.
Development not permitted
E.1 Development is not permitted by Class E if—
(a)
permission to use the dwellinghouse as a dwellinghouse has been granted only by virtue of Class M, N, P or Q of Part 3 of this Schedule (changes of use);
.
(b)
the total area of ground covered by buildings, enclosures and containers within the curtilage (other than the original dwellinghouse) would exceed 50% of the total area of the curtilage (excluding the ground area of the original dwellinghouse);
.
(c)
any part of the building, enclosure, pool or container would be situated on land forward of a wall forming the principal elevation of the original dwellinghouse;
.
(d)
the building would have more than a single storey;
.
(e)
the height of the building, enclosure or container would exceed—
.
(i)
4 metres in the case of a building with a dual-pitched roof,
.
(ii)
2.5 metres in the case of a building, enclosure or container within 2 metres of the boundary of the curtilage of the dwellinghouse, or
.
(iii)
3 metres in any other case;
.
(f)
the height of the eaves of the building would exceed 2.5 metres;
.
(g)
the building, enclosure, pool or container would be situated within the curtilage of a listed building;
.
(h)
it would include the construction or provision of a verandah, balcony or raised platform;
.
(i)
it relates to a dwelling or a microwave antenna; or
.
(j)
the capacity of the container would exceed 3,500 litres.
.
E.2 In the case of any land within the curtilage of the dwellinghouse which is within—
(a)
an area of outstanding natural beauty;
.
(b)
the Broads;
.
(c)
a National Park; or
.
(d)
a World Heritage Site,
.
development is not permitted by Class E if the total area of ground covered by buildings, enclosures, pools and containers situated more than 20 metres from any wall of the dwellinghouse would exceed 10 square metres.
E.3 In the case of any land within the curtilage of the dwellinghouse which is article 2(3) land, development is not permitted by Class E if any part of the building, enclosure, pool or container would be situated on land between a wall forming a side elevation of the dwellinghouse and the boundary of the curtilage of the dwellinghouse.
Interpretation of Class E
E.4. For the purposes of Class E, “purpose incidental to the enjoyment of the dwellinghouse as such” includes the keeping of poultry, bees, pet animals, birds or other livestock for the domestic needs or personal enjoyment of the occupants of the dwellinghouse.
For the building to benefit from permission by virtue of the GPDO it must comply with
all the limitations and conditions, where these childrens play structures fail is the provision of a raise platform, whether they fail elsewhere will often depend on the specifics of the case.
If the building fails to benefit from permission by virtue of the GPDO it will need express planning permission from your local authority, you would need to look at your local Council's development order, any supplementary planning guidance, which policies apply t
http://www.legislation.gov.uk/ukpga/1990/8/section/171Bo your land and also teh NPPF as to whether they would likely support an application.
It is worth also noting that if you choose to erect the strucure in the hope that no one reports you take dated photograph once it is complete. Four years after the strucutre has been substantially complete it will become immune from enforcement action as per S171B of the Town and Country Planning Act 1990. If you erect the structure without planning permission you do so at your own risk.
Apologies for any formatting or spelling, grammar I have rushed this somewhat in my lunch break. Also whilst I am happy to help it would be sensible to either seek advice from your local authority or seek some independent planning advice from someone local to you, I offer my advice simply as a payback to the forum for help i have received in the past.