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lsBITUMINOUS SURFACINGMATERIALSMany of the County’s roads and footways aresurfaced with bituminous material or ‘black top’and this is an entirely appropriate and traditionalproduct.

Originally, the vast majority of roads in Suffolkwould have been consolidated earth reinforcedwith local stones, flint and gravel. Tar was thenused to bond crushed stone together to form asmooth surface. With the rapidly increasingdemands of vehicular traffic the use of bituminousbased materials became almost universal forroads in both rural and urban areas, particularlywith the use of surface dressings.

In general, the majority of surfacing on roads ismachine laid. Contractors will charge by theweight of materials or the area to be laid.Materials laid by hand should be avoided and onlyconsidered on footways and areas of roadinaccessible by a machine. Hand laying large areascan produce a varying degree of surfaceirregularities. Laying small areas on either road orfootways will be more expensive when comparedto larger areas because of the set up costs ofequipment, transport and labour.

Historic photographs illustrate the simplicity of surface treatments as shown here in Wickham Market

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lsExtensive use of bituminous surfacing for bothfootways and carriageway, in busy areas such astown centres, can create a lack of contrastbetween the two. This can cause conflictbetween pedestrians and vehicles. In order toimprove these areas other materials should beconsidered for use alongside black top to giveclear messages to the highway users.

In sensitive areas such as conservation areas or inthe vicinity of listed buildings, the widespread useof bituminous finishes is sometimes inappropriateas the material may not complement or enhancethe character of these important historiclocations. The use of alternative products such asgravel surface dressing or stone paving should beconsidered especially in the more importantspaces such as squares or along the main streets.

In some rural or village environments black topcan be appropriate however given its low keynature.

A mix of surface dressing and wearing course with exposed gravel aggregate was used in order to improve thespace for pedestrians at The Hill,Wickham Market

In Easton a simple blacktop footway is enhanced bythe grass verge and granite setts forming the kerb

The use of blacktop can be appropriate in manylocations but it can emphasise the dominance ofmotor vehicles

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The appearance of black surfaces can be‘modified’ by surface dressing or by specifyingparticular additives or aggregates in the mix. (Forfurther advice on the use of surface dressing inenhancement schemes, see the Suffolk SurfaceDressing Manual).

Traditionally, many of the roads and footways inthe County would have been constructed using agravel aggregate. However, its use on thecarriageway is restricted because of its poor skidresistance and its durability in comparison withcrushed rock aggregates.

The use of gravel in surface courses is onlyacceptable in areas where traffic speeds aresufficiently low and issues of durability areadequately addressed. Where it has been used insome enhancement schemes, clear epoxy coatedgravel has been rolled into the gravel basedsurface course to provide an instant effect. Overtime the gravel in the asphalt will ‘wear’ throughfurther enhancing the surface.

The choice of stone colour to be applied to thewearing course surface or within the asphalt itselfcan have a significant impact on the visualappearance of the surface: both gravel and pinkgranite give a warm effect in contrast to blue orgrey stone.

In the north east of the County, includingLowestoft, it is traditional to use limestoneaggregate in the wearing course, especially forpavements. Over time, with wear, this produces amuch lighter grey surface.

When adding aggregates to surface courses careshould be taken that any reinstatements followthe original specification, otherwise patches willbe clearly visible.

In general the use of pigments should be avoided;they are rarely appropriate, especially in sensitiveareas because they often weather poorly and cancause maintenance problems.

Gravel

Red granite

Limestone

Stone colour can have a significant impact on the appearance of black surfaces:

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lshas a very poor skid resistance and shouldonly be used in areas where the speeds arenormally not in excess of 10 mph or otherlocations where the risk of accident wouldbe low. It can be used with other stones toincrease the skid resistance of the finishedproduct.

5. Gravel chippings can be used with a clearcoat binder to enhance the look of thefinished product although this is expensive.However this will also have low skidresistance.

Gravel tinted thin surfacing6. Where a surface is to be trafficked by slow

moving and/or heavy vehicles a thinsurfacing may be laid using one of theproprietary thin surfacings butincorporating 50% of flint gravel. Thiswould not be suitable for areas with fastmoving traffic or hazardous locations.

Technical Information1. There are three principle surfacing

materials used in Suffolk. Hot RolledAsphalt (HRA), Dense BituminousMacadam (DBM) and proprietary thinsurfacings.

2. All tend to produce a uniform blacksurface appearance. Their appearancecan be enhanced by a number ofmethods.

Limestone aggregate3. Limestone from approved quarries in

Derbyshire can be used as coarseaggregate. This will give a soft greyappearance to the finished surface.Limestone polishes readily and canproduce a surface which is slippery in wetconditions and it should not be used wherethis would create problems.

Gravelled asphalt4. Local flint gravel aggregate can be used to

enhance the appearance of asphalt.Unfortunately flint gravel, like limestone,

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Ker

bsKERBS

The separation of the carriageway from footwaysdates back to the mid 18th Century when thefootway was surfaced with stone slabs set at ahigher level and sometimes edged with a stonekerb. This could be granite or other stone such asYorkstone. Stone drainage channels (or gutters)were often installed alongside.

Stone kerbs had to be transported to Suffolk andtherefore were expensive. Large dressed kerbswere therefore usually only found in importantstreets with smaller rougher versions usedelsewhere. In some urban areas, stone quadrantswere used to turn corners.

Later, concrete kerbs were introduced, madelocally from gravels or other aggregates. Thesewere considerably cheaper than stone kerbs.

In some towns, such as Felixstowe, Sudbury andBungay, Staffordshire blue clay kerbs and channelswere laid with stable pavers to match.

Old kerbs should be retained wherever possible, if necessary relaid, or used elsewhere in thevicinity as they contribute greatly to the historiccharacter of an area. Where additional reclaimedkerbs are required they should be chosencarefully to match the originals.

Even second hand modern concrete kerbs have amore weathered look and can help soften theimpact of kerbing in comparison with newsmooth concrete.

Historically, granite kerbs were used with rivenYorkstone flags (Sudbury)

Old granite

Blue clay kerbs and channels

Old concrete kerbs

In sensitive locations, new stone kerbs arepreferable to concrete, even if concrete slabs areused.

Much of the natural stone kerbing now available isimported, often being transported from countrieslike China and Portugal. The sustainability issuesinvolved in using these products should thereforebe given careful consideration.

The technical specification for stone kerbs shouldbe carefully considered – kerbs may be dressedon two faces only, the others being left rough incomparison, making them difficult to lay andcreating a potential for movement to occur overtime, especially if regularly over-run by heavytraffic.

Stone kerbs are available in a variety of coloursranging from pale to darker grey, pink and bluegreen. It may be difficult to match old kerbs withnew if the original quarry has closed.

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‘Riven’concrete

New granite

Exposed aggregate concrete

New Yorkstone

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bsA variety of exposed aggregate kerbs are available

with varying colours and cross sections.

In sensitive areas and those of a more ruralcharacter, kerbs with a rectangular cross sectionwill have a less urbanising effect than the modernhalf batter shape.

Concrete imitations of stone kerbs are alsoavailable: small module ‘riven’ or kerbs imitatingdressed stone. These are normally rectangular incross section.

Kerbs can be used in a variety of ways – normallyas a raised edge of footway, or to enclose an areaof grass or landscaping. In rural and villageenvironments, kerbs should ideally be avoided butif absolutely necessary to protect, say, a villagegreen, one option is to lay stone or riven concretekerbs on a batter with the earth covering the topface to give a more natural look whilst stillprotecting the area from over-run and erosion.

Kerbs may also be laid flush to an area todemarcate an edge or contain an area of surfacedressing. If flush kerbs are likely to be overrun byvehicles, careful laying is needed to avoidmovement.

New granite kerbs reinforce the historic character ofThe Thoroughfare in Woodbridge

New granite kerbs and channel laid in the High Street,Saxmundham

Kerbs laid on a batter so that soil can be laid over thetop (where over running is a problem the kerb can belaid at a steeper angle)

Flush exposed aggregate concrete kerbs in Lowestoft

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Technical Information1. Natural stone kerbs should be supplied

from a single source for each project toensure consistency from both a visual andtechnical aspect.

2. The rock type should be granite or similarigneous rock. Other rock types may onlybe used where approved by the SCC AreaMaintenance Manager in consultation withthe SCC Conservation Officer.

3. If reclaimed natural rock kerbs are usedthey shall be redressed before use. Ifthere is a variation in sizes in the supply ofkerbs the equivalent sized kerbs must beused together.

4. If reused concrete kerbs are to be laidthey shall be examined for frost, scuffingand other damage and any kerbsdamaged such that the structural integrity,durability or appearance is impaired shallbe rejected.

5. Kerb heights should generally be 125mmor 160mm at bus stop locations.

6. Kerb heights at vehicle accesses shall be25mm and at cycle and pedestriancrossings should be 0- 6mm.

7. Foundation depth shall be at least 150mm.

8. Concrete grade of foundation to beC12/15.

9. Kerbs shall be laid on a wet concrete bedor mortar bed. Kerbs with less than 90%contact area shall be rejected.

10. Radii or quadrant kerbs shall be used. Thecutting of short lengths of straight kerbsfor forming curves shall not be permitted.

11. Where flush concrete kerbs are likely tobe overrun by vehicles, they shouldgenerally be no longer than 450mm.

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gTACTILE PAVINGTactile (or “Blister”) is a term given to a range ofpaving that bears a discernible raised surfaceprofile which aids the partially sighted and blindpeople in locating pedestrian crossing points.They are also used as a hazard warning on flightsof steps or where footways are shared withcyclists.

The colour of tactile paving is also used to denotedifferent meanings to the partially sighted,normally red at controlled crossing points, buff atuncontrolled.

A small area of buff tactile laid in a narrow footway

Changes in levels at crossing points can have a significant impact on the laying pattern of materials

In this scheme at Needham Market pink tactile pavingwas selected as it related to the chosen palette ofmaterialsCorduroy tactile paving at a bus stop in Lowestoft

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g In conservation areas and other environmentallysensitive locations, provided that there is asignificant measure of visual contrast, it isacceptable to use alternative tactile materialswhich are less intrusive.

Traffic Advisory Leaflet 1/96“Traffic Management in Historic Areas”produced by the Department of Transportstates:

“It is accepted that in historic areas some colourcontrasts may not be considered acceptable: buff

or grey materials can therefore be used asappropriate rather than pink.”

Routed Yorkstone tactile slabs are manufacturedas a standard product and steel or brass ‘blisters’can be added to stone or concrete slabs that havealready been laid or they can be installed by thesupplier before delivery.

Guidance on the use of tactile paving is given bythe Department of Transport, but carefulconsideration should always be given in everyinstance to the detailing and paving patterns toensure a satisfactory design solution.

Technical Information1. The layout of tactile paving should

normally comply with DfT ‘Guidance onthe use of Tactile Paving’..

2. Generally buff paving should be used atuncontrolled crossings and red paving atcontrolled crossings.

3. In conservation areas the colour of thetactile paving can be altered to suit thesurrounding built environment. Preferablythe paving should be of a contrastingcolour to the surrounding footwaymaterial. Traffic Advisory Leaflet 1/96:‘Traffic management in Historic Areas’ alsoprovides guidance on the use of tactilepaving in these areas.

Some alternative tactile materials

A B

C D

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Black concrete cast with a tactile finish

Routed Yorkstone

Brass studs in riven Yorkstone

Steel studs in sawn Yorkstone