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  • HPH373: Using a willow bed to treat sewage – with Laila Dudhill

    HPH373: Using a willow bed to treat sewage – with Laila Dudhill

    Laila Dudhill explains some of the challenges she faced when planning her new build home at the bottom of a sloping field. Not only did she have to deal with drainage across the site, diverting the natural flow of water away from the house, but also come up with a foul drainage strategy that would off-set phosphate discharge into the local watercourses.

    Interview with Laila Dudhill

    Laila Dudhill has a 40-acre farm in Herefordshire, in one of the river catchment areas in the county that is sensitive to phosphate pollution. Her land is partly situated on heavy clay and on a gradient, so a lot of thought has had to go into dealing with all aspects of water run off and foul water treatment. In the early stages of planning her project she developed rheumatoid arthritis, which increased her determination to step away from the responsibilities of the farm and influenced her designs for the new house.

    The original barn and field

    ‘Class Q’ permitted development allows for a change of use

    Class Q planning permission allows for a change of use from agricultural buildings to residential dwellings. Laila’s barn was a 1990s steel frame structure and the Class Q permitted development allowed her to build to the same footprint, same envelope and same size. The steel frame was a problem for Laila as the steels would have created thermal bridging and heat loss. This meant she had to go back to the Local Authority after receiving Class Q permission and gain consent to replace the steels (in other words, build new). She also needed to alter the angle of the roof slightly so that it would be optimised for solar PV. This resulted in the pitch being slightly higher than the original barn.

    The old barn is dismantled

    Any new home must address phosphate pollution

    Herefordshire has a large number of intensive poultry units, which has resulted in high phosphate levels in the River Wye and the River Lugg. The Council is concerned about more phosphates coming from the foul drainage of new properties, so every planning application in this area must demonstrate what measures will offset the phosphates.

    There are ways to off-set phosphate discharge

    Laila explains that her foul drainage strategy will double the offset requirement. Her main system is a willow bed and a septic tank, rather than the more common biodigesters. A biodigester requires a large drainage field, which was a problem for Laila being on heavy clay soil. It also cleans the effluent much better than a septic tank, so wouldn’t provide enough nutrients for a willow bed. 

    The willow bed satisfied her planning requirements, but Laila has been able to continue to add to her phosphate off-setting in various ways. Taking agriculture off the land gives you a phosphate credit along with planting trees, particularly fruit and walnut trees.

    The contours of the land and the flow of water

    The natural water flow was straight past the barn

    The site’s drainage has been of particular concern

    Topographical surveys and drainage studies were carried out, including percolation tests to determine the speed water drained through the ground. The field in front of the house was clay, with very poor drainage, whilst the woodland at the back had extremely fast drainage. Neither situation is good for a drainage field. Either the water sits on top of the soil with potential run-off to the watercourse or it goes through the soils so fast that the nutrients aren’t retained in the soil. The septic tank and willow bed will retain all nutrients from her foul water system, with periodic de-sludging of the tank required.

    Having lived on the site since 2006, Laila had a good knowledge of how water flowed through the site to a pre-existing pond (that’s shown on Ordnance Survey maps). She tells us about springs that issue from within the woods, but that she had not experienced any flooding around the barn until last winter, which was then repeated this year. She is not in a flood zone and believes this is because she is on a slope, so water doesn’t rise around the property but flows past in extreme weather. A new flood alleviation pond has been created to hold excess surface water and the recent severe weather tested the system and showed that some adjustments were needed.

    A flood alleviation pond was dug

    Water is piped from the flood alleviation pond under Laila’s driveway, to the head of a brook that emanates at the edge of the woodland and also picks up the woodland springs. Water from the brook eventually feeds into the River Arrow within the Lugg catchment which is why the foul drainage from the house needs to be managed separately to the rest of the surface water run-off.  The rain water which falls on the house can simply be discharged into a free draining area of the woodland.

    Digging the giant willow bed

    Lining the willow bed

    Back-filling the willow bed

    The willow bed is an effective way to treat the sewage

    From the house, all the sewage goes into a septic tank, which links into a willow bed. This is lined so nothing can escape into the surrounding soil. The bed is backfilled with soil and planted with willow, which uses the water from the foul drainage in transpiration and uses the nutrients to grow. Laila is researching which varieties to grow, how close to plant them and how often they should be coppiced so that people will want to use the willow.

    The willow bed requires a lot of space

    Laila’s drainage consultant Alan Corner looked at a Danish study and an Irish study to work out how big the willow bed needed to be. The specification is based on the number of bedrooms in a house, as that generally determines occupancy. Strictly speaking, Laila’s is a four bedroom house, although she will usually be living there on her own. The specification for the willow bed has come out at 47 metres by 8 metres, about the size of an Olympic swimming pool!

    “I’ve coined a phrase, I’m going to grow a crop from my crap”

    Financially, it’s been expensive and probably it would not be an option for most people, but Laila says it was a really interesting process and a good test case.

    Get recommendations when building up your team

    Laila tells us that she has found the whole process positive, with one thing organically leading to another and people always happy to explain things and answer questions. Initially she had a recommendation for a planning consultant, who then guided her through the planning application process and put her in touch with a groundworker. She interviewed a few architects and selected one.

    Building a house can be stressful

    Even when people are fantastic and things are exciting, Laila points out there is still stress, which is not ideal for her rheumatoid arthritis. But she has support from her rheumatology team, who try to keep her condition tolerable.

    Dividing the farm has helped finance the new home

    Laila feels fortunate that her farm can be divided quite nicely into two (by the main road), so she can sell the farmhouse, land and outbuildings on one side, whilst keeping the rest for her new home. She is currently still living in the farmhouse, but will need the sale to go through in order to complete the build.

    Embracing simplicity makes it easier to build and achieve the Passivhaus standard

    Laila’s father was an engineer and her mother was a mathematician, and so Laila understands the benefits of keeping things simple. Passivhaus Consultant Nick Grant has been advising and she has been happy to implement all his recommendations. This ultimately leads to doing more with less.

    The foundations for the new home are dug

    The binding layer of the foundations

    The foundations are nearly complete

    The groundworks and Isoquick base are now complete

    Laila’s structural engineer was happy that the stony ground the original barn was sitting on was sound for an Isoquick insulated raft foundation. The site was excavated down to around 750mm below the finished floor level and then built up with a sub-base material, which was compacted, and a final 50mm fine drainage stone to create a flat surface. The Isoquick raft sits on top of this followed by a layer of concrete, so they are ready for the superstructure.

    We will revisit Laila later in her build to hear the next steps in her journey.

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  • HPH154 : The challenges of building a new home in a rural community – with Jeremy Harris

    HPH154 : The challenges of building a new home in a rural community – with Jeremy Harris

    Jeremy Harris, a scientist by background, wanted a low energy house for his retirement. He talks about the initial stages of his self-build project: finding a plot of land and obtaining planning approval.

    Jeremy Harris

    Interview with Jeremy Harris

    Jeremy Harris, a scientist by background, wanted a low energy house for his retirement. He first came up with the idea that he might like to build a house around ten years ago.

    It’s important to fully understand the beginning of the self-build process

    Jeremy found television programmes and magazines rarely touch on finding a plot, designing a house to fit that plot, and the people you have to employ to do all of that work. It can be very expensive, costing thousands of pounds for planning consultants, architects, building control, etc.

    Plots can seem very nice on websites but look nothing like the photographs in reality

    Finding a plot of land was extremely hard. The Harrises drove several thousand miles, visiting disappointing plots. They began by looking at what they wanted to build, but Jeremy concluded this was the wrong way round: first find a plot, then determine what type of house will fit on it.

    Having walked away from one likely prospect, by chance they found their plot of land 16 miles from where they were living. It was too overgrown to see properly and fenced so they couldn’t get into it, but looked like it might be exactly what they wanted: facing south (i.e. good solar access) and in a sheltered valley.

    There's a plot in there somewhere!
    There’s a plot in there somewhere!

    Buying a plot is not the same as buying a house – ensure services will be available

    When buying a plot of land a solicitor can tell you if there’s a public footpath on it but won’t find out if you’ve got water, mains electricity, mains sewage or even if the boundaries are in the right place.

    Services in rural areas are often stretched to the limit. Jeremy had to ask the relevant utility companies if they could supply:

    1. Electricity? Fortunately there was plenty of power on their doorstep.
    2. Water? Companies have a statutory duty to supply water but the issue is cost. They’d have to dig up a lane for 140 metres and although Jeremy shopped around (anybody with a licence can do the digging), the minimum cost was still £24,500.
    3. Mains sewerage? There’s no statutory requirement to supply this and the cheapest the water company could provide it was £14,800.
    4. A new phone connection? Telecoms companies see self-builders as developers. If there isn’t enough capacity, they can charge whatever they want to lay a new multi-cable.

    As services would cost so much, Jeremy renegotiated the price accepted. The land hadn’t sold for eight years so he persuaded the vendor to knock off a substantial amount.

    Many building plots have boundaries in the wrong place where the Land Registry is concerned

    Plots of land don’t have registered boundaries as a rule. There was a boundary error affecting the Harrises’ plot meaning the house approved to go on it wouldn’t fit.

    The process for resolving boundary errors is complex and time consuming. It’s up to the vendor to do it, so you have to persuade them to spend money with Land Registry to get title plans amended. This often affects adjacent houses, as well as your plot, involving lenders as they have a right on the title.

    A stumbling block can sometimes turn out to be an opportunity

    It took them a year to get their boundary error resolved, but this allowed time to plan the project properly.

    Jeremy wrote a brief with eight key design points but the architects he approached didn’t seem to understand the role of design with low energy houses. Looking further afield for a Passivhaus specialist was an option, but thinking the distance might make communication difficult Jeremy decided he’d design their house himself.

    So the year was productively spent:

    • Evolving designs for the house
    • Tracking down the local Openreach engineer who offered help at no cost, as Jeremy planned to dig trenches on the plot and an underground network would solve local problems with overhead cables and trees
    • Discovering a borehole was possible, at half the cost of mains water
    • Planning a sewage treatment plant, costing around £3,500; much cheaper than digging up the lane

    This avoided inflaming an existing situation with the neighbours, as the plot had a chequered planning history, and saved money too!

    The borehole
    The borehole

    Once the principle of development is established by an approval, it’s extremely difficult for planners to remove it

    The Harrises’ plot had planning permission for a little stone bungalow that they didn’t want. As the local authority had approved the principle of putting a house on the plot, their plan was to submit a new application.

    Areas of outstanding natural beauty, conservation areas and proximity to listed buildings put constraints on what you can build. For example, needing to have all the external materials approved, as was the case with Jeremy’s house.

    Good communication paves the way for a smoother planning application process

    In Jeremy’s area, seven objection letters result in the application being referred to a planning committee, where emotions come into play far more than planning law.

    A previous application for the plot resulted in 14 objections at Parish Council level and dozens of letters. To mitigate objections for their application, Jeremy spoke to every neighbour, sent them regular update newsletters and even Christmas cards.

    He also made scale models, enabling all interested parties to understand the design before the planning application went in. His wife could look inside the rooms to see whether they were big enough, and the neighbours could see what the house might look like in the landscape. And the scale model played an important part at the Parish Council planning meeting, where applicants aren’t allowed to talk.

    model-sw-view-small

    “We had several cases where objectors turned to supporters”

    Jeremy eliminated concerns by talking them through with neighbours:

    Genuine concernsWhat Jeremy did
    New house would overload the sewage systemExplained they were putting in a sewage treatment plant instead
    Height of the house might block views or cast shadowsUsed the 3D scale model to show that the house would be set into the hillside (3m down)
    Being overlooked in their back gardenUsed the model to show that the garage blocked the view (neighbour was also happy the garage protected their vegetable patch from the wind)

    Engaging with local people is important but Jeremy adds a caveat: be cautious and put your foot down if neighbours ask for too much; at the end of the day it’s your plot and your house.

    The Harrises got through the planning stage with no letters of objection at all, so the decision was down to a Planning Officer purely based on the law and planning policies for the area, and approval was granted.

    Transcript

    Download a transcript of the interview with Jeremy Harris

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