Guide To Creating The Perfect Garden Building

The Vivid Green guide to creating the perfect garden building

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Contents Index Introduction What is important? Insulation Glazing Heating Lighting Size and shape External finishes and materials Foundations Internal finishes Planning Other hints and tips Gallery Price guide Further information Other structures

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Appendix A. Standards for sustainable buildings

Introduction A garden building, particularly one you are going to use year round, is a major investment. There are a bewildering array of designs, styles and materials to choose from and, unless you have some experience of building, the choice may appear overwhelming. This guide is intended to help you make the right choice for your situation. As well as our own views based on several years experience of designing and installing low energy buildings, we include links to independent sites and suppliers. We hope it is comprehensive but please email us with your suggestions for other relevant topics and any other feedback to make this a better guide for everyone. What is important? If you are considering buying a garden building, whether office, studio, workshop, gym or home cinema/play room, what should you look for? There are four main aspects to consider: insulation glazing heating (& lighting ) size and shape finishes and materials

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Insulation Insulation is fundamental; you will be sitting in an isolated structure with no rooms around you so it is essential there is sufficient insulation to keep you warm in Winter and cool in Summer. Sufficient insulation is a subjective term so, given the isolated nature of the building, there should be at least as much insulation as is required for a new house, if not more. Gardens can also be surprisingly noisy: children, building work and traffic in particular so if the insulation can reduce this too, that is a bonus. The table below shows the standards required for new housing in the UK alongside the level of insulation in a typical garden building and what can be achieved with a higher specification. Vivid Green 150

Vivid Green 100

Bdg regs standards¹

Typical Garden Office/Room U value² WmThickness ²/K 45mm 0.57 45mm 0.57 0 1.20 1.90 frame

U value² WmU value² WmThickness U value² Wm-²/K ²/K ²/K Roof insulation 153mm 0.14 128mm 0.17 0.16 - 0.25 Wall insulation 128mm 0.17 78mm 0.28 0.30 - 0.35 Floor insulation 100mm 0.22 100mm 0.22 0.22 - 0.25 Windows/doors 1.15 pane 1.15 pane 1.8 - 2.0 1.80 frame 1.80 frame ¹ Building Regulations Part L 2002 ² U value calculation: BRE U value calculation version 1.08. Calculation method: BS EN ISO 6946 Thickness

What this means in practice depends on many factors such as construction method and materials, insulation type, quality of glazing, location, desired internal temperature etc etc. However, as a guide, the difference in heating bills between a 10 sq metre typical garden building and the Vivid Green 100 specification will be about £120 a year at current prices. As well as potentially saving money, a higher level of insulation creates a more comfortable environment: smaller differences in temperature during the day more even temperature throughout the year (cooler in Summer, warmer in Winter) There are many different types of insulation on the market with many claims about the sustainability of the different types. For an unbiased guide go to: www.greenspec.co.uk Glazing You will probably want a good deal of glass to create a light interior but be careful there is not so much that you roast in Summer. It is surprising how little glass you need to give sufficient light and generate a little warmth (solar gain) when the sun is shining. If some of the windows face South, it is helpful to have a good overhang on the roof or a brisesoleil to shade the windows in the height of Summer. While on the subject of glass, good quality windows and glazed doors pay dividends. Glass is a very poor insulator and even double glazed units let through about 6-7x as much heat as a well insulated wall. So, choose windows with a U value (the heat transfer co-efficient of materials) better than the 1.8Wm2k required by the UK Building Regulations to reduce heat loss. Where possible, check the ‘whole frame’ U value rather than just the ‘centre pane’ value since a poorly made frame can let out a lot of heat. Special coatings and Argon filled gaps between panes are available as well as triple glazing and special arrangements to reduce sound transmission.

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www.energysavingtrust.org.uk/Home-improvements/Home-insulation-glazing/Glazing www.greenspec.co.uk/html/product-pages/vikingdouble.php www.viking.ee/en/products/ Apart from their contribution to heat loss, the quality of windows and doors will have a big impact on your enjoyment of the space. Especially if you are leaving valuable equipment in the building, have a look at the locks on doors and windows. Are doors triple point locking? Can the windows be locked at all and ideally, can they be locked in a slightly open position? Hardwood windows are expensive but there are many other cheaper options which also provide long life. Check on the quality of the timber treatment which should ideally be applied in the factory rather than on site. Are the beads which hold in the glass nailed or pinned? If nailed, the nails are very likely to rust, stain the timber and let in water. The best windows have no nails and a metal bottom bead which is the one which always rots first. Factory treated and painted softwood windows are an economical option which should not need re-painting in less than 10 years but Aluminium clad timber is never likely to require painting. A couple of opening windows on opposite sides of the building will create a good through draft but the other windows can be fixed pane. Make sure several windows have trickle vents to ensure adequate ventilation and that any glass below 800mm from the floor is safety glass. Heating Heating options are many and varied but one of the simplest and most comfortable is underfloor electric heating which gives a very even temperature and will allow you to set the thermostat several degrees below the norm. Other benefits include: no wall space lost to radiators/heaters no hot surfaces even temperature throughout compatible almost any flooring.

with

If close to the house it may be possible to install a wet heating system ie: underfloor hot water heating which, depending on the efficiency of the boiler may be a very economical solution.

http://www.ebeco.com/en/index.php Lighting Lighting a well designed building providing plenty of natural light is not a major concern

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and, except for winter, artificial light should not be needed during daylight hours. If you want stylish, low energy lighting then there is now a good choice including lights from these two companies: http://www.tp24.com/ http://www.greenled.co.uk/ Size and shape This is largely down to personal taste but there are some technical considerations. Flat roofs have a bad reputation but, properly designed with a high quality roof covering this type of roof should last just as long as a pitched roof. Rubber membranes should give a 15-20 year life if properly installed. As well as being more economical than a pitched roof, there are situations where it looks appropriate and it is one of the solutions to the challenge presented by recent changes to the planning rules (see below).

A flat roofed art and music studio

http://www.fra.org.uk/

An apex roof clad with cedar shingles

A pyramid shaped roof for doing the books

Where space allows, a mono-pitch or ‘pent’ roof can look very distinctive. If the pitch is at least 14 degrees, preferably 18, then many options are available for covering including cedar shakes and shingles, slates etc. Roofing materials with a high recycled content are coming on to the market including ‘eco-slates’ manufactured from recycled plastic and which are indistinguishable from the real thing. Cheaper options include asphalt tiles or sheet but neither has a very long life.

Firestone permaroof membrane

www.permaroof.co.uk/

Cedar shingles

www.ajsmith.uk.com/cedarshingles

Recycled plastic eco-slates

www.athyecoslate.com/

Green roofs can look attractive though they need regular maintenance if they are not to look very scruffy after a year or so and there is a significant premium to pay for the additional materials. Also, if you are a keen gardener, you will probably want to collect the water rather than reducing run off. A roof of 10 square metres will usually provide at least 800 litres of rainwater at the start of the Summer. Black plastic guttering is fine, especially if not visible but galvanised steel offers a very attractive alternative. The most economical shape for a garden building is square since a long, narrow building will be much more expensive for the area achieved. (A 16 sq metre square building requires a wall run of 16 linear metres whereas an 8 x 2 metre building giving the same

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floor area, requires 20 linear metres of wall or 25% more!). However, it is largely a matter of personal preference, knowing how you will use the space and how the building will fit into the garden and complement or enhance surrounding buildings. www.lindab.co.uk/frameset www.greenroofstoday.co.uk External finishes and materials Many garden buildings are clad in timber but check to see what type of timber is used and how much maintenance will be required. Softwood, especially if it needs repainting or treating every other year, may not be as cheap as it seems in the long run. Most people have enough work maintaining their house without spending weekends maintaining another building! A durable timber like Cedar will require no treatment and even cheaper options such as Douglas Fir and Larch which are semi-durable will last for 15-20 years without treatment and much longer with the occasional coat of preservative. www.trada.co.uk/index.html www.stourhead.com/sawn_timber.htm Foundations Most garden buildings are sufficiently lightweight not to need concrete foundations. 150200mm of compacted hardcore over sub-soil is one option but a cheaper one is to remove the top layer of vegetation and install an interlocking plastic system which is backfilled with pea gravel. The eco-base from Swift Foundations is one such system designed specifically for garden buildings. Sloping sites, newly made ground and areas prone to flooding all require special attention so if in doubt ask your supplier or a structural engineer

http://www.swiftfoundations.co.uk/ http://www.istructe.org/Pages/SeDefault.aspx Internal finishes

On the inside, one of the major considerations is fire resistance. In most cases garden buildings do not have to comply with Building Regulations and provide 30 minute fire resistance. However, there may be circumstance where you would prefer the additional piece of mind which comes from a fire resistant interior. A fireboard/plasterboard finish is the normal choice and will give a high quality surface which allows cabling and sockets to be recessed. Other options are available and special finishes such as pin board can be very useful. Sundeala pin board is made from 100% recycled newsprint.

www.bbs-ltd.com/drylining_fire.htm www.sundeala.co.uk/sundeala.htm www.norbord.com/SterlingOSB_Splash.shtml Many people will use their garden building for music making and sound insulation therefore becomes an issue. This is a huge subject and very technical. Differences between attenuation, absorption and transmission as well as different wavelengths quickly confuse most people. Plenty of advice is available and solutions need not be especially expensive. In general they also offer fire resistance. The following web sites explain how to go about sound proofing. http://www.acoustic-supplies.com http://www.skanda-uk.com

http://www.soundstop.co.uk

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Plasterboard with a skim finish, recessed wiring and sockets provides a neat wall finish

Flooring is an important consideration too. Even with door mats and asking visitors to remove their shoes, there is the potential for the floor to get wet and muddy after the walk down the garden. Carpet is, therefore, generally not a good idea but rubber or one of the modern linoleum products is a practical alternative: relatively cheap, easy to clean and hard wearing. Wood can also be good though grit and dirt can quickly scratch the surface. For a hardwearing surface, rubber is a good choice with a huge range of colours and patterns available: www.jaymart.net/sarina.php

www.nora.com/com/uk/products.html Planning The UK Government changed the planning rules relating to outbuildings on 1 October 2008 so that, within 2 metres of any boundary, no structure (even a shed) can be higher than 2.5 metres. http://www.planningportal.gov.uk/wales/genpub/en/1105619048902.html. With the need to raise the building off the ground plus the thickness of floor and roof insulation, this presents an interesting design challenge. Flat roofs are an obvious answer. With headroom between 2075 and 2150mm (6’ 9” to 7’). buildings such as those below offer a simple solution with adequate headroom for most people.

Penthouse 8

Penthouse 7.5

However, more attractive roof shapes are possible and the following sketches give an idea of the options available if the building can be sited at least one metre from the boundary. Flat roof with lantern The simplest way of adding headroom and light is a lantern. Glass lanterns can be very expensive but polycarbonate versions offer a great alternative. Double and triple skinned versions offer superior thermal and sound insulation. Headroom is typically 2075 to 2150 (6’ 9” to 7’) plus an extra 300-500mm (1’ -1’ 7”) under the lantern.

http://www.nationaldomelightcompany.co.uk/ Shallow hip

A shallow pitch of at least 15 degrees offers the option of cladding the roof with cedar shingles and just a few more degrees opens up lots of options including eco-slates (imitation slates manufactured from recycled plastic). Because of the need for a slope, the height of the walls (eaves height) is reduced but greater headroom can be achieved throughout the rest of the building. Typically

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1800mm (5’ 10”) at the eaves, headroom increases to 1930mm (6’ 4”) 500mm in from the walls and is 2600mm (8’ 6”) in the centre. Shallow hip + gablets When the garden is a little bigger there is the potential to add ‘gablets’ to the roof: triangular gable ends. These can be left solid but using triangular windows makes a very attractive roof shape and provides additional light. Headroom is similar to the shallow hip design above. Both shallow hip designs require one wall to be inset by 600-1000mm to allow installation of doors. This creates an attractive porch or veranda depending on size.

Other hints and tips A porch offers some protection from the rain for you and your papers, computer etc while you open up.

Install twice as many power points as you think you will need (4 doubles as a minimum) When running the power cable from the house to the garden building, run several lengths of ethernet, telephone and alarm cable at the same time even if you are not going to use it. Conclusion We hope you have found this guide useful. It is designed to answer most of the questions which arise when people consider installing a building in their garden. The advice and information is intended to be objective but, since we believe that there is more value to be had from a building which is comfortable all year round and requires little maintenance, there is an inevitable bias towards high levels of insulation, high quality materials and components and low maintenance finishes and products. If, in the long run, this approach saves customers money and a few tonnes of CO 2, so much the better. We hope you find your space for life as rewarding as we find ours.

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Gallery: examples of bespoke designs

Flat roof office, Harpenden; the prototype!

Shallow pitch roof to bookbinding workshop, London

Apex roof office, Aldeburgh

Flat roof studio, Exeter

Pitched roof clad in cedar shingles; Surrey

Pent roof office in London

Pent roof office, Oxfor

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Bespoke designs to meet current planning restrictions on height

Standard designs to meet current planning restrictions on height

Penthouse 8

Penthouse 7.5

Price guide Most customers requirements are so specific that a bespoke design is the only was to meet their needs. However, standard designs are an economical option when economy is more important. Standard designs (see gallery) work out at £9-10,000 including VAT for 7.5-8 sq metres internal floor area. Investment in a bespoke design depends on roof shape and covering, number and size of windows and doors etc. but, as a rough guide, allow £1500 per square metre for up to 8 square metres, reducing to £1300 a square metre for up to 15 square metres. For buildings in excess of 25 square metres, prices can reduce to approx. £1000 a square metre including VAT. Prices include design, delivery, foundations, installation, internal wiring and finishes etc. The only exclusions are trenching and cabling between house and garden building and painting. Further information, installations and testimonials For more information contact Neil Johnston on 01582 469076 or email [email protected] or visit the web site: www.vividgreen.co.uk. A small building is on permanent display at Townsend Nursery, Townsend Lane, Harpenden, AL5 2RH. We also have a growing number of installations of all shapes and sizes throughout the country so please call us to find one near you Feedback The content of this guide is based on those questions most often asked by customers and those enquiring about garden buildings. If there are topics you would like covered please let us know.

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Other structures Larger buildings The design principles and construction techniques used in our garden buildings are applied to larger structures up to 300 square metres to provide comfortable, efficient, low maintenance structures for a variety of uses.

A WC and shower block for Scout and Guide camp site

A dormitory for a residential centre

A concept design for a holiday eco-lodge

A 50 place nursery

Pavilion Timber framed and clad with canvas roof liner and synthetic tensioned fly sheet. One double and one single bedroom plus sleeping/play loft. Additional insulation offers scope for year round use. Separate brochure available.

Canvas lodges Timber framed, canvas covered lodges for Summer/one season use. Timber floor, windows and doors. Simple, robust accommodation for campers, cyclists, walkers, summer camps etc. Separate brochure available.

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Appendix A. Standards for sustainable buildings Not particularly relevant for garden buildings but if you are interested in more sustainable construction, there are many claims for green buildings but how do you know which ones really mean something? We claim that our garden offices, studios and workshops are low energy because we design them to at least achieve the standard of insulation required for new housing as defined in Part L of the Buuilding Regulations. Most clients opt for the Penthouse 100 spec but some are persuaded by the higher level of comfort and reduced heating costs from adopting the higher Penthouse 150 spec. For larger buildings there are several standards which are worth considering. BREAM has been around for a long time and now encompasses a range of assessments for many different buildings. http://www.breeam.org/ The Government issued the Code for Sustainable Homes last year which, as the name suggests, relates to housing with Level 3 the minimum required for publicly funded housing and Level 6 the aspirational goal. http://www.communities.gov.uk/planningandbuilding/buildingregulations/legislation/englan dwales/codesustainable/ Finally and, in my view, most relevantly, there is the system being promoted by the Association of Environment Conscious Builders (AECB). This is very simple to understand with both a prescriptive and performance based approach and plenty of practical advice on how to use the standards. Essentially Silver should be the minimum to which anyone considers building with the Gold standard somewhat higher in performance than even the German Passiv Haus standard. http://www.carbonlite.org.uk/carbonlite/ Whether you adopt one of these standards as a goal in its own right or use the guidance as a way of improving an existing design, the benefits can be significant. As with all building, incorporating energy saving measures at an early stage in the design is far easier than adaptation or retrofit in the future. And, in most cases, the premium can be as low as 5-15% of the capital cost for a lifetime of savings.

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Notes and questions

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© Vivid Green Ltd; April 2009.

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