My chum just had a 25x45m sand paddock put in and it cost just shy of £8k not including the surrounding fencing. This was not the cheapest quote she got but the guy came well recommended.
I had mine built cheaply 50m x 20m for around the £8k mark a couple of years ago. Used a man with a digger and arranged my own delivery of stone, membrane, sand etc.
i reckon for about 10k you can get one by a reputable person, along with mirrors at each end (like the free standing ones at medstead) then Corroy can admire herself too
DIY was about £9000 up here, for a rubber school. I think it was going to be anout £14000 to get it done by someone else. But this is using cheap materials I think.
£18-£20k for 20x40 herringbone drained sand and rubber surface is my quote just waiting for dam planning to come through and work can start!!!!!!! hopefuly save a bit in places using Dad's lorry to haul materials and put up our own fencing..... its the digging and drains that cost but to me most important as need to beable to use it whatever the weather!!
If you want a decent one built by a reputable specialist in menages which will come with a warrenty in case anything goes wrong then for a 20 x 40 you want to allow £25,000.
I have seen too many cheeply built menages where the drainage or membrane fails and the whole thing becomes unusable.
Remember that you need planning permission to put one in and don't forget the floodlighting on the planning application.
Just done a bit of estimating and I can see why they are so expensive lol I estimate for a 40 x 20 m appro £22k
Here goes ...
Site Preparation clearing site of vegetation £600
Machine excavation to remove topsoil n/e 200 mm thick £480
Excavate to reduce levels not exceeding 1.00m dp £360
E/O for breaking out obstructions £30
Disposal of ground water £200
Disposal of excavated materials off site £6000
Filling to make up levels MOT type 1 200mm thck £4000
Sand blinding 50 mm thck £2400
Compacting £400
Membranes one layer of terram £800
School surface allow £50pc/m3 approx 75mm thck £3000
Fencing Item £2500
Drainage to storm soakaways £2500
So if you can keep the excavated materials on site you will save money instead of carting it off site. Also if you bind the excavated materials you can reduce your fencing requirements. I am not totally sure of the construction for a school never measured on but I think this is pretty close.
We paid £18k for a 20x60 sand and rubber , post and 3 rails from a locally recommended company - Charles Britton wanted £32k fort he same spec.
Add around £1k for lighting (depending on how much cable you need) - ours worked out at £970 but we put all the cabling in ourselves and just got sparky to connect it up (even then sparky was £700)
Best 18k we spent - well after buying the house and building the stables