Paving for Rain - Brochure

meeting the latest rules for paving around the home – guidance for professionals including:• Planners• Surveyors• Conveyancing lawyers• Designers • Landscapers• Contractorswww.paving.org.ukApril 2012pavingfor rainIntroductionWhen most people are planning a new or replacement drive, patio or path they probably don’t think about where the rainwater landing on it will end up. But taking a responsible approach to drainage is essential to reduce flooding and pollution from impermeable surfaces. Government has recognised this issue with important changes to permitted development rules and other recent legislation requiring sustainable drainage systems (SuDS) for paving around the home. Failure to implement these measures will substantially damage the fight against flooding and lead to a less sustainable local environment. This guide aims to help local authorities to understand the importance of the measures and how to interpret them so that they can be correctly applied on the ground. It also provides surveyors, conveyancing lawyers, designers, contractors, landscapers and other professionals with the information they need to advise their clients correctly, avoiding issues of planning enforcement and complications with home sales. Other documents referred to in this guide are numbered and their details given at the end, together with a Glossary of Terms.Interpave is the trade association for precast concrete paving and has been involved with SuDS and permeable paving from the start, working alongside governmental and other organisations. In fact, government guidanceo1 on paving front drives refers specifically to the Interpave website and guides. More information can be found on our website www.paving.org.uk, where the Commercial section has a wealth of information for all professional users. There is also a dedicated Domestic section for householders.one www.paving.org.uk – the paving resourceBackgroundTo begin with, it’s worth explaining what the problems are with drainage today, how they came about and why the government has introduced new rules to solve them.What’s wrong with our drainage?Most rainwater falling on natural countryside simply passes into the ground. But continuing growth of our towns and cities is causing an increasing amount to be captured on impermeable surfaces and flow into sewers. Today, most rainfall running off drives, patios and other paving around the home will end up in the sewer.In the past, sewers and roads were designed to remove water as quickly as possible to stop flooding occurring where the rainfall hit the ground – and they are still good at this job most of the time. When the Victorians built the sewer networks still in use today, Britain was far less populated and towns and cities much smaller. So, these sewers, and some later systems, did not put too much water into rivers and streams in the past. But as more and more development has taken place the amount of rainfall running off streets, car parks, building roofs and drives has increased. Existing drainage systems cannot cope and this causes flooding of rivers and streams. This problem is even worse with heavy storms and more of them are predicted in future with climate change. Why are our rivers and streams polluted?The surfaces of roads, car parks and driveways collect pollution – from car exhausts, tyre-wear, oil leaks and other sources – and when it rains this gets washed into rivers and streams. Again, as towns and cities have grown this has become more noticeable and is causing real problems for the environment. A lot of older sewers are known as ‘combined sewers’ carrying both rainwater and ‘foul water’ from toilets, baths, sinks, etc. They often have overflows that operate in heavy rain, diverting all the flows – including raw sewage – into rivers and streams, with serious consequences. As development increases and more rainwater runs into the sewers, the overflows are operating more often and therefore increasing pollution.95%5%30%Agricultural70%70%30%95%5%Countryside95%5%30%Agricultural70%70%30%95%5%Towns & citiestwo www.paving.org.uk – the paving resourcewww.paving.org.uk – the paving resourceSo, what can be done about it?It is now well recognised that Sustainable Drainage Systems (or SuDS) technology must play an essential role in curbing flooding and pollution from rainwater runoff. SuDS manages surface water by slowing it down (known as attenuation) and cleaning it up (by filtering). It uses techniques that aim to replicate, as closely as possible, the natural drainage from a site before any building work or paving. The new government rules and guidance in this document are all based on established SuDS principles.Why do we need to act now?There is no doubt that climate change is resulting in more frequent and heavy rainstorms, particularly in summer. Simply allowing rainwater to run straight off roofs and impermeable paving into drains increases the chance of sewers flooding local homes, as well as streams and rivers flooding vulnerable towns and cities. Remember the summer floods of 2007? The Environment Agency estimated that over two thirds of the 57,000 homes affected were flooded not by swollen rivers but by water running off paving or overloaded drainage systems serving them. threeWhat other problems are being caused?Sealing up areas with impermeable materials such as asphalt (or ‘tarmac’) or solid concrete stops rainfall soaking into the ground. Without this ‘groundwater’, the water table levels drop which makes water shortages worse, with streams and ponds drying up. It also causes damage to nearby trees as they are deprived of water and could also affect the foundations of a home, particularly on clay soils that dry out and shrink. All these problems are made worse when gardens are covered with impermeable paving to make a parking space or patio which just let the water run straight onto the road or into the sewers.What difference does paving around the home make?Of course, a small area of paving in isolation is not going to cause major flooding – but it is the cumulative impact of lots of gardens being sealed up that creates real problems. For example, The Greater London Authorityo2 has estimated that paving over front gardens for car parking that has already occurred in the city is equivalent to an area around 22 times the size of Hyde Park or 16 times the size of the new Olympic Park or the size of 5,200 football pitches. Just imagine the rainwater runoff in a storm from an area that large.www.paving.org.uk – the paving resourcefourThe New RulesA government-backed report (The Pitt Reviewo3 ) which looked at the 2007 summer floods and government strategy (Future Water) both made various recommendations for use of SuDS and new controls to paving and drainage – some affecting private gardens and drives. These recommendations have been taken up with changes to planning rules in both England and Scotland.How will SuDS be implemented?For some time now there has been wide-ranging encouragement to use SuDS. Government planning policy throughout the UK already requires SuDS on all developments wherever possible, as does the new draft ‘National Planning Policy Framework’, and SuDS are an important part of the ‘Code for Sustainable Homes’. The new Planning Permission rules aim to apply simple SuDS techniques to paving around existing homes. They relate to houses and bungalows only, as paving around blocks of flats and maisonettes will still require planning permission. Along with Interpave’s guidance, they are based on established SuDS principles.Planning PermissionBefore the changes, paving anywhere in a garden with any materials was considered to be ‘permitted development’ – effectively, an automatic planning permission without needing a planning application. The changes take away permitted development rights from new or replacement drives or other paving between a house and the street, unless it is permeable paving or drains water onto a permeable garden area within the property. Otherwise planning permission will be needed before installing new, or replacing existing paving.In England, these measureso4 took effect in October 2008 and apply to paving:• over 5m2• in the front garden only.In Scotland, similar measureso11 apply to work initiated after 6 February 2012 and apply to paving:• of any size• between the house and any street (therefore not just front gardens).Both English and Scottish governments refer to a guideo1 on permeable paving from the Department of Communities and Local Government and this, in turn, refers to the Interpave website, this document and our homeowners’ guidanceo8 for more information.What happens if homeowners decide to apply for permission? If the proposed paving does not meet the ‘permeable’ requirements for permitted development, a planning application will be required, along with drawings and a fee, which could take at least 8 weeks to process. Anyway, government planning policieso5 encourage planners to insist on SuDS (such as permeable paving), so an application should be rejected.www.paving.org.uk – the paving resourceWhat if homeowners go ahead anyway?If homeowners go ahead without permission, the local authority Planning Enforcement Officer should take action demanding an application or removal of the unlawful paving. Increasingly, local residents and Parish Councils concerned about flooding are alerting Enforcement Officers about unauthorised, sealed-up front drives in their areas. The application of these rules has now been reinforced by a recent planning appeal decisiono10 clarifying several aspects of acceptable ‘permeable paving’.What happens when a house is sold?Both vendors’ and buyers’ solicitors will want to make sure that all necessary planning permissions are in place, otherwise this could be a problem for the buyer in future. Solicitors are becoming more aware of the new rules and should be making specific pre-contract enquiries about driveways. Without planning permission, a new or replacement drive that doesn’t meet the rules could delay or even stop a house sale and add to costs. Where permeable paving or other SuDS systems have been used in front gardens, permitted development will apply and solicitors’ enquiries will simply be satisfied. For the same reasons, valuers and surveyors should also check the lawfulness of paving around the home when inspecting a property, to avoid any problems early.Flood and Water Management ActNew legislationo6, covering England and Wales, will include requirements for SuDS on any construction work which affects the ability of the ground to absorb water, when it takes effect (probably in October 2012). Related draft National Standards and other regulations are still under discussion at the time of publishing this guide and include some proposed exemptions. In particular, the requirements will not apply to the ‘permitted development’ discussed earlier (using permeable paving or draining water onto a permeable garden area), as long as the work does not cover 100m2 or more. If the proposed paving does not meet the ‘permeable’ requirements for permitted development, an application for permission will be needed to the ‘SuDS Approving Body’, which could well be turned down. There will also be enforcement procedures if unapproved work is actually carried out and the same problems with selling a home discussed earlier could occur.Visit the Interpave Commercial website www.paving.org.uk for the latest information on progress with the act.Other MeasuresThe government is also considering other steps suggested in the Pitt Review. Local authorities already have ‘Article 4’ powerso7 to suspend ‘permitted development’ rights and stop the laying of sealed-up surfaces where they pose a local flooding problem – for example onto a neighbouring property or a road. This is now a simpler and quicker process for local authorities than in the past. Creation of a new ‘Statutory Nuisance’ is also being considered which could be served by local authorities on homeowners to reverse work carried out around the home that aggravates surface runoff flood risk.fivesixConcrete Paving and SuDS SolutionsIn order to meet the latest requirements using concrete block and flag paving, two different types of SuDS are covered here and, in more detail, in our homeowners’ guidanceo9 : • Concrete Block Permeable Paving – this is different to conventional block paving because it allows rainwater to filter through gaps or joints between the blocks into a permeable sub-base below with enough space to store the water for a short time. Cellular concrete units are also available, designed for grass to grow through, which work in a similar way (for more information visit individual Interpave Members’ websites).We should also remember that water is an increasingly rare asset and we need to take a more sustainable approach to using it. Rainwater can be stored for some time below permeable paving then pumped up for plant watering and car washing – even during hosepipe bans – or to flush toilets.• Conventional Concrete Paving Blocks or Flags with Rain Gardens – here, water from conventional concrete block or slab paving simply runs off into a landscaped depression in the garden to allow the water to be stored temporarily. Then, the water can soak into the ground or evaporate. Concrete channel units can help collect and direct the water towards the rain garden. The same principle applies to taking water from the paving into a soakaway on site.In both systems, water is held back during heavy storms to avoid flooding and filtered to remove or trap pollution. What happens to the water after that depends on the ability of the ground to absorb water (known as permeability) and whether it is intended to make use of the rainwater.With good ground permeability (such as sandy soil), the water can simply soak away into the ground. This is the cheapest option and helps replenish the water table and sustain trees. With poor ground permeability (such as heavy clay), some of the stored water is collected and gradually soaks away or discharges into sewers or streams but with far less impact than direct drains.www.paving.org.uk – the paving resourceseven www.paving.org.uk – the paving resourceConcrete Block Permeable PavingThere is a growing choice of concrete blocks and paving slabs available from Interpave manufacturers, designed specifically for permeable paving. Essentially they have the same impressive performance as conventional precast concrete paving products, being slip resistant, durable, strong and sustainable. And today there are more shapes, styles, finishes and colours than ever to give you real freedom of choice.The difference with permeable paving is its enlarged joints, filled with a permeable aggregate specifically chosen for each product – but never sand (which is used with conventional block paving). This ensures that water will continue to pass through the joints over many years. The materials used below the blocks are also specifically selected to accommodate water, unlike conventional drive and road construction. Local authorities may ask homeowners for evidence that their new permeable paving is installed correctly to meet the rules, such as a letter of confirmation from a reputable contractor. To be sure, use a paving contractor who is a member of Interlay: www.interlay.org.uk or who is registered with an Interpave manufacturer member’s scheme.How can you tell the difference?Conventional block paving is not designed to be permeable. Its sand filled joints soon clog up to provide a sealed-up surface and the material below is not intended to handle water. Although looking similar to conventional block paving, permeable paving should have permeable aggregate (looking like coarse, sharp or crushed stone) filling the joints and under the blocks, not sand. In addition, a recent planning appeal decisiono10 highlights that a permeable sub-base must also be used below to comply, not standard ‘Type 1’ aggregate, which has sand and silt filling voids (as shown).Where can you find out more about permeable paving?Each Interpave manufacturer Member offers a specific permeable paving system with impressive choice of designs, surfaces and colours to suit every style of property. Simply select Interpave members from the table on page one and visit their websites for more information. Our homeowners guidanceo8 provides more information on how to design and construct permeable paving.Type 1 aggregate for conventional block paving is not permeable when compacted.Typical permeable sub-base aggregate has voids between for water.??eight www.paving.org.uk – the paving resourceHow does permeable paving work?Permeable paving is specifically designed for a dual role, acting as the drainage system as well as supporting vehicles. At the same time, many pollutants are substantially removed and treated within the paving layers before the water leaves it. Concrete block permeable paving can be laid level and still avoids puddles without the need for drainage gulleys and pipes. It also provides a safe, firm surface for everyone, including wheelchair users and people pushing prams, unlike gravel and other loose materials that may also satisfy the permeability rules. But the Accessibility Building Regulationso9 don’t allow these loose materials for entry paths and drives to new homes.Concrete block permeable paving with infiltration to the ground.Concrete block permeable paving with pipe to drains or harvesting system.Around this home, rainwater runoff collected from all impermeable surfaces including roofs and paths, together with the 60m2 permeable drive itself, passes into the lined permeable pavement which contains a concealed sump. Here, a small pump is used to draw off the harvested water, in this case for outside uses, via a tap and hosepipe.This is a more sustainable approach to car washing with most of the water automatically treated for reuse as it passes through the permeable paving.nine www.paving.org.uk – the paving resourceConventional Concrete Paving Blocks or Flags with Rain GardensConventional concrete block and slab paving provides an attractive, safe and functional surface for drives and patios. But rather than using traditional gullies and drains leading to sewers, the paving is designed to direct water onto the garden. A depression in the garden is formed to allow the collected water enough time to soak into the ground: this is known as a ‘rain garden’. Small areas can, in most cases, be drained straight onto garden areas without a rain garden. Concrete dished channel units are useful to collect and direct the water towards the rain garden.Rain gardens can simply be shallow grass depressions or with the right planting offer the extra benefit of attractive and robust green spaces that require little, if any, watering. Where ground conditions demand, rain gardens can have stone filled trenches below the depression. There is also potential for drains to collect the water for re-use or connection to sewers. If you are connecting to a mains drain, permission may be needed. The rain garden can be planted with a wide range of appropriate plant varieties available from garden centres or decorative stones laid over the surface. Where can you find out more about rain gardens?Our homeowners guidanceo8 provides more information on how to design rain gardens for conventional precast concrete paving around the home.Conventional precast concrete paving to rain garden with infiltration to the groundten www.paving.org.uk – the paving resourceGlossarySub-base aggregate (for conventional concrete block paving) – A dense mixture of sand and gravel compacted to give a hard surface on which to build the driveway. Often referred to as DoT ‘Type 1’ aggregate.Permeable pavement sub-base aggregate – Crushed rock or similar material that does not have fine material in the spaces between rock pieces, allowing water to flow easily through the voids. Proprietary coarse graded aggregates specifically for permeable paving are available from many suppliers. Attenuation – Slowing down and temporarily storing rainwater flow from hard surfaces, so it can enter the drains more slowly, as it would from grassed areas.Permeability – A measure of how fast water can flow through the ground.Type 1 Aggregate – see above.Permeable Aggregate – see above.Water table level – The level at the top of the water in the ground. If a hole is dug in the ground that goes below the water table it is the level of standing water in the hole after it has stabilised.Conventional concrete block paving and flags – Block paving and slabs that do not allow water to soak through them into the sub-base.Concrete block permeable paving – Strictly speaking, this is the surface of block paving with special gaps between each block that allows water to soak into the sub-base. Sometimes it also describes a concrete block permeable pavement – The whole construction including the concrete block permeable paving, laying course and the layer of permeable pavement sub-base aggregate.Laying course aggregate – A layer of fine aggregate that is placed over the sub-base to make it easier to lay the blocks to the required levels and falls. For Conventional concrete block paving and flags this is sand. For Concrete block permeable paving it must allow water to flow through it easily and so a fine (nominal 6mm) aggregate is used.Impermeable Membrane Liner – A plastic sheet that is water tight. It should be 0.5mm thick (2000 gauge).Surface Water Sewer – A pipe in the ground that conveys collected water and removes it from a site. Older sewers remove sewage (known as foul water) as well as rainwater and are known as combined sewers. New developments have separate sewers for foul and rainwater.Drain – Common name for smaller sewers that are located within the boundary of a house. Connect into main sewers that are usually (but not always) in the street.Conventional drainage system – The network of sewers below an area, including private drains, main sewers and ancillary structures such as manholes and gullies.Dished channel – U-shaped precast concrete units available from Interpave members in a range of colours which can match the paving if desired.Fin Drain – A flat drainage system which channels water through a filter into a drainage core before it enters a drainage pipe, thereby reducing the likelihood of the pipe becoming blocked with silt. Fin drains take up little room and work efficiently.Geotextile – A fabric, made of plastic fibres, that is permeable to water but stops soil being washed through. References1. Department for Communities and Local Government. Guidance on the permeable surfacing of front gardens. September 2008. http://www.communities.gov.uk/publications/planningandbuilding/pavingfrontgardens2. Greater London Authority. Crazy Paving – The environmental importance of London’s front gardens. September 2005. www.london.gov.uk3. Sir Michael Pitt. The Pitt Review: Lessons learned from the 2007 floods. 2008. The Cabinet Office. 4. The Town and Country Planning (General Permitted Development) (Amendment) (No. 2) (England) Order 2008.5. Planning Policy Statement (PPS) 25 – Development and Flood Risk. (For England). Planning Advice Note (PAN) 61 – Planning and Sustainable Urban Drainage Systems. (For Scotland). Technical Advice Note (TAN) 15 – Development and Flood Risk. (For Wales). National Planning Policy Framework. March 2012.6. The Flood and Water Management Act 2010. Defra. Draft National Standards for sustainable drainage systems (and related documents). December 2011.7. The Town and Country Planning (General Permitted Development) Order 1995, Article 4.8. Interpave. Domestic Design Guide – Responsible rainwater management around the home. November 2010. www.paving.org.uk9. The Building Regulations 2000. Access to and use of buildings – Approved Document M. 2004. 10. Appeal Decision APP/P3610/C/09/2110696. The Planning Inspectorate. 11. The Town and Country Planning (General Permitted Development) (Scotland) Amendment Order 2011. AcknowledgementsInterpave would like to thank the following for their help in producing this document:Robert Bray of Robert Bray Associates.Martin Levick, DipTP, MRTPI, MInstLM, Senior Planner (Enforcement) at Cheltenham Borough Council.Bridget Woods-Ballard, HR Wallingford.Written and produced by Hodsons Ltd for Interpave.eleven www.paving.org.uk – the paving resource© BPCF Ltd 2011www.paving.org.uk60 Charles Street, Leicester LE1 1FB United Kingdome: info@paving.org.uk t: 0116 253 6161 f: 0116 251 4568INTERPAVE IS A PRodUCT ASSoCIATIoN oF ThE BRITISh PRECAST CoNCRETE FEdERATIoN LTdt: 0116 253 6161 f: 0116 251 4568e: info@britishprecast.org www.britishprecast.orgt: 0116 222 9840 f: 0116 251 4568 e: info@interlay.org.uk www.interlay.org.ukHEIDELBERGCEMENT GroupFormpave