Pete recently did an interview on BBC Radio 4 - You and Yours - which investigated a case history of failed cavity wall insulation.
Well... if you say menage to a Frenchman he'll think of households - as in 'menage a trois' - and certainly won't connect you with horses. The correct term for a schooling area for horses is manege!
The most common size is a standard 40 x 20 metre school. This is quite adequate for most domestic needs, but you may need to extend it to 60 x 20 if you intend to do a lot of jumping or dressage. Don't just add 5 metres here and there, because you will lose the standard circle sizes needed for dressage training. Commercial yards have completely different needs, and often have to cater for more than one lesson taking place at any time - which means a doubling or even tripling of the standard surface areas.The vast majority of maneges built are 40 x 20 metres.
Depending on the final surface, this figure can vary a great deal. There is, however, a bottom line below which you really cannot go - this works out at around £15,000 and is based on the appropriate quantities of materials described below, with a rough allowance for labour and machinery to build it. If someone quotes less than this - they are cutting corners somewhere - go through the quote with a toothcomb - check specifications for materials, and insist on samples of everything before committing. I've seen schools built that have cost upwards of £100,000, but never much below £18,000.
There are a number of essential aspects to a manege. Each of these must be present in one form or another to enable the finished product to work properly. If you cut money off the project, you will end up compromising one or another of these stages, with the inevitable result that you have a wet, soggy school in winter.
Site selection is not just an aesthetic process. You need to ensure that it is high enough to be drainable - and that there is sufficient fall on outlet pipes to be able to carry this water to a nearby main drainage channel - nearby stream, ditch or stormwater drain. Bear in mind that the volume of water that is produced by a well built manege in even an average rainstorm is quite phenomenal - a 4 inch outlet pipe can frequently be seen to gush water at at flow rate of several thousand gallons an hour. It is vitally important to ensure that the surface you are to work with is flat. On sloping ground, we use a system called 'cut and fill' - digging out the high bits, and putting that material into the low parts. It's important that you realise that this process must be done properly. Any material which is used to fill low areas MUST be compacted and allowed to settle properly - natural settlement of soil and clay is a process that can take up to 12 or 18 months to achieve full compaction. Initially you can expect slumping and settlement of up to 25% of the initial volume. This means that if a contractor digs out a metre of material and dumps it on the 'downside' of a slope, you can expect that side to end up settling down a good 6 to 12 inches depending on how well the contractor compacted it when he put it there. If you dont allow for this slumping, your school surface will end up with dips and hollows in it, or at worst, will slope badly in the direction of the filled area. To avoid this, you can make up areas that need filling with hardcore instead of soil, which doesnt slump significantly. This then leaves a problem of disposal of excavated material - often we can find a hollow in a field somewhere that needs filling, or at worst, it has to be carted away. Of course, there is no reason why a relatively flat site cannot have a manege built on top of it - the fencing is used to retain the various layers, by using timber or concrete boards attached to the fence posts. Bear in mind that the total thickness of various layers can be 350 or 400mm. Note that topsoil should always be removed.- it contains a lot of organic material which rots and blocks drainage.
There are a number of options available for a drainage structure - but they all have one thing in common - channelling water away from the surface as quickly as possible. The most common arrangement is to run a central 'spine' down the middle of the school - the centre line - and pipes are then laid at an angle to this in a herringbone pattern, which reach out to the outer edges of the school. The herringbone pipes should be laid at no more than 5 metre intervals. All drains should have a minimum gradient of 6mm per metre length, giving the total fall in drainage from one end of a 20 x 40 school of about .25 of a metre, or 10 inches. You can vary this pattern if, for example the school is built on a hillside - the drains can be laid to discharge water onto the downslope side. Care must be taken to ensure that you dont end up with a concentrated gush of water being discharged onto the hillside and causing erosion.
Drains must be the perforated plastic 100mm land drainage type, laid in a trench roughly twice the depth of the pipe, which is lined with geotextile membrane. The pipe is laid in the trench, which has been lined with membrane, and the trench filled with clean pea gravel. The central spine is then connected to a discharge main, usually a solid 4 inch stormwater pipe is used, which is then directed into the nearest drainage channel such as a ditch.
Once the drainage channels are complete, the entire area is covered in geotextile membrane. This seals the drainage channels and prevents mud from mixing with either the drain channels or the next layer to be added - the actual porous drainage bed lying underneath your surface material.
This is an essential part of any manege - it acts as a reservoir for water falling in heavy downpours, and allows rapid dispersal of water from the working surface. It must be non degradable material - one of the most popular used these days is clean road planings. Crushed rock is ideal - BUT - do NOT use oolitic limestone, which gradually breaks down and produces a very sticky, muddy clay which blocks the drainage system very quickly (hard, grey limestone - if washed, is OK). Igneous rocks such as granite and dolerite, and slate being ideal. Crushed flint is an option in Norfolk. I prefer to use 40mm clean stone - this is by far the best size - 6" of 40mm clean stone will provide the best drainage bed you could wish for, and is easy to level and spread. Crushed hardcore is often suggested. This is fine so long as it is CLEAN, and does not contain crushed old bricks. The old red bricks that are often present in hardcore will break down and produce sticky clay as well (they are made from brick clay in the first place). If there is plenty of crushed concrete, without the fine dust that often accompanies it, you won't have a problem. You MUST insist that any hardcore used is screened to remove all fines, and that ONLY material from 25 to 75 mm in size is delivered. Even a moderate proportion of fines will slowly work their way through the hardcore and end up sitting on the membrane underneath, blocking it. The total thickness of this layer should be at least 100mm (4 inches) or more. Translated into volumes and tonnes, you are looking at around 80 cubic metres, (at 100mm thickness) or roughly 180 tonnes - assuming decent sized lorries carrying 12 to 17 tonnes, you are going to need at least 10 lorry loads. It needs to be settled and rolled to ensure it can't move below the top surface with the weight of horses working on it.
On top of the drainage bed, you need another layer of membrane. This keeps the working surface completely separate from the drainage bed. There are two reasons for doing this - one, it is then impossible for the work surface to fill the pores of the drainage bed and block it. Two - you are at liberty to change surfaces simply by raking the material off the membrane layer, and replacing it - the drainage bed is still kept intact and fully functional. Membrane should be tacked or stapled to the boards around the edge of the school, and the joints should be well taped to stop them from opening up or slipping sideways when the surface is being put down.
I have described fencing on the Do It Yourself page - How to Build Your Own Manege... with some diagrams - have a good look at this. We normally cut square posts, but you can use either square cut rails or rounded, sepending on how you like it to look.
This is the point at which we see the most variance. To some extent it is covered in the next section, selection of appropriate surface, but we'll briefly discuss surfaces here too. To protect the membrane which covers the drainage bed, we usually use a layer of clean, washed silica sand. This is NOT the material sold in Cornwall and Devon as silica sand, which is a clay ridden by-product of china clay mining. It usually comes from the quarries in Cheshire which are worked for foundry sand, and contains little or no fines and impurities. You need to allow for a depth of at least 50mm, preferably 100mm. Translated into volumes and tonnes, you are looking at around 80 cubic metres, (at 100mm thickness) or roughly 140 tonnes - assuming decent sized lorries carrying 12 to 17 tonnes, you are going to need at least 9 or 10 lorry loads.
There ARE surfaces around these days which don't need sand underneath them. If you are using the shredded carpet / insulation material derived from scrap cars, a 6 to 9 inch layer of this material can be laid directly on top of the membrane. ( There are some vendors who insist that with this material you dont need a membrane over the stone - DON'T omit the membrane - its a fatal error you'll regret!) I would still protect it with a little sand anyway - just to prevent sharp hooves nicking it, but it comes down to choice and budget at this point. Essentially, if the material you are using doesnt break down in any way (eg shredded carpet / insulation, medical rubber or shredded window seals) you can get away with it. Shredded car tyres do tend to break down and block drainage beds after a while, so be careful that if using this material, you make sure it cannot get to the drainage bed. It is also on the list of nasty environmental stuff that councils won't approve these days on account of toxic runoff. Our worst case surface is shredded wood - several vendors are offering shredded pallets, claiming that they dont break down - I've seen a surface made from this material which in 2 years had almost rotted away. Bark chip is the same - it rots down, breaks up, and produces large amounts of dust in summer. Steer clear from it if you can afford to - its a false economy.
This is a tricky question to answer at the best of times. We always say to people that they need to go and ride as many surfaces as they can before making a decision. If you can't ride it, ask people. Try to ask professionals who know the effect the surface is having on their horses and riding - and ask showjumpers as well as dressage riders. You will need to give thought to the use to which your manege is to be put - if you are mainly jumping, it is more important to protect the membrane with sand, and to select a surface that gives a little natural spring - if dressage, try to avoid anything that your horse sinks into or that causes him to drag his feet. In general, surfaces for jumping tend to be bigger, springier materials than those for dressage - the shredded carpet / insulation material is ideal for this, although it can be used for dressage too, because its fairly light, and tends to bed down over time into a springy mat. Silica sand with shredded door seals, medical rubber, or chopped telephone cables are all good surfaces for flatwork. The best surfaces these days tend to contain wax - it holds everything together, stops the sand blowing away, and provides a springy, resilient surface - but... it's expensive, as the best always is.
Don't give the job to someone who claims they can do the job for less than the figures we are quoting on these pages. If its cheaper, they have to be leaving something out - and you will regret it for ever and a day! Get them to quote on a detailed specification, and watch them like a hawk when they do the job to ensure they are putting in the materials and quantities specified and quoted on.
All too often we are asked to comment on an old school that just doesnt work the way it used to. There are two main problems that crop up again and again. They are:
Incorrect or inadequate drainage bed beneath the surface.
Inappropriate surface
Yes. No exceptions. Anywhere. Depending on the authority, they usually need 5 sets of existing and proposed plans and elevations together with engineering details covering drainage, construction, fencing and detail of where the water runoff will be directed. You will have to provide samples of the proposed surface.