All Need To Know About Soakaways When Building An Extension

Surface Water Drainage and Soakaways on a House/Home Extension

Now I bet you cant wait to read about this one can you? Come on let’s get through it together and then you will still have time to catch the end of Eastenders.

There are two types of drainage in operation in your home: surface water and foul water. Your new extension will definitely involve at least one of them.

Let's deal with surface water drainage. That’s rainwater to you and me basically.

It lands on your roof, goes via your gutters and downpipes to your surface water system. A lot of properties don’t have a surface water drainage system and your drawings may well show rainwater draining into what’s known as a soakaway.

A soakaway can be as simple as a hole in the ground filled with rubble and coarse stone with a drainage pipe laid to it in order to disperse the rainwater.

It's not rocket science, and again, it will be constructed to the specifications laid down by the Building Inspector to your builder. He may make your builder construct a honeycomb brickwork chamber and infill from there, but he will certainly want to look at the soil in which it is situated.

The soil will have to have good drainage properties – there is no point in sinking a soakaway in clay or in an area with a high water table.

Unless you wish to farm rice or some other semi aquatic crop of course.


Soakaway Construction

The soakaway must be at least 5 metres from the extension and 2.5 metres from your neighbours’ fence.

The pipe flowing to the soakaway should be 100mm underground waste ideally, but the Building Inspector may settle for 75mm, and it should be laid to a fall of 1:40.

Most Local Authorities will insist on at least a 1 metre cube, but if the man with the clipboard says “ bigger, wider deeper!” then your builder will have to nod respectfully, pick up his spade and carry out his wishes, whilst muttering darkly through gritted teeth.

And it’s going to start raining again.

The stone infill of the soakaway should surround the pipe and finish about 100mm above it.

An impervious layer should then be placed on top. This can be anything from a tarpaulin (I prefer blue ones) to a slab of concrete. Topsoil, turf, and bake for 15 minutes.

Your builder may choose to buy a ready-made soakaway and there are many available these days.

They tend to be circular sections of concrete or plastic that can be linked together to give the required depth and then finished with a suitable cover, but if he can, and its okay with the Building Inspector, he will opt for a basic hole in the ground and fill it with rubble.

And, let’s face it, by the time it blocks up, he will be long gone and relaxing in his timeshare in Magaluf.