Your technical questions answered

Have you ever wondered what some of the reference terminology used in our industry actually means? Can you calculate the number of setts in a tonne, decipher a bull nose from a chamfered edge and understand that SUDS isn’t just bubbles left in your bath?

We have put together some typical questions you may have around industry terminology and general technical understanding, with of course some basic answers that will hopefully help broaden your knowledge a little.

What is CE marking?

In 2013 CE marking of construction products became a mandatory obligation for all products that are covered by a harmonised standard to have a declaration of performance. By affixing the CE mark HPL takes responsibility for both the performance and conformity of the materials we supply.CE_mark

What are the typical BSEN Standards covering our market for performance of material selected ie granite paving?

There are a suite of European standards covering the testing and performance of all paving products from BSEN 1338 for concrete pavers to BSEN 1344 for clay, Hardscape can advise which are relevant to your needs and the minimum requirements of your specified materials.


What is a tactile?

Tactiles are used as delineators within a surface to either guide or warn of a hazard for example either at the side of a road or at  station platform, generally blisters are used at crossing points and corduroys are used to either guide along a footpath edge or warn at the top of a flight of steps.

Shiraz RED granite tactile


What is a typical average slip resistance for a flamed finish granite sett?

Both the HSE and UK guideline for slip/skid resistance as well BSEN 1341 gives a value of anything over 35 as being safe, annexe C of BS7533 part 12 gives a PTV (pendulum test value) value of 40 for pedestrian use and 45 for trafficked areas. Typical unpolished slip resistance example for Royal White granite: 65.5 (wet)

What’s the build up to show a typically flexible and typically rigid construction method?

This would normally be worked out by your site engineers based on CBR value’s and traffic loadings but generally both build ups will be similar in materials thickness.

For example:

Bedding 30mm

Base 100-250mm

Sub-base 150-350mm


What is an acceptable tolerance measurement for granite paving?

BSEN1341 4.2 tables 1 / 2 / 3 shows the varying permissible tolerances for stone paving depending on plan and thickness dimensions but on a 80mm thickness it would be +/- 4mm.


What is efflorescence and how must I specify material to deter this?

Efflorescence is a powdery deposit of salts which forms on the surface of bricks and mortar. It is usually white but efflorescence may be yellow, green or brown. A definition for efflorescence is a staining of brickwork, masonry and concrete, caused by salts being washed out of construction materials, and being deposited on the surface of building materials by the evaporation process of water.


What are typical bedding and jointing materials?

The most typical bedding and jointing materials are sand and cement though these days many applications look to proprietary mortars which can contain a polymer to aid adhesion and strength.

Can you show me a typical DOP certificate example?

Hardscape can supply on request both CE and Declaration of Performance certificates for the materials we supply.


What is a typical or average segment/chord length?

By definition a line that links two points on a circle or curve. Below is a formula for the length of a chord if you know the radius and central angle:

Chord Length B

r  is the radius of the circle
c  is the angle subtended at the centre by the chord
sin  is the sine function

or below is a formula for the length of a chord if you know the radius and the perpendicular distance from the chord to the circle center. This is a simple application of Pythagoras’ Theorem:

Chord Length A

r  is the radius of the circle
d  is the perpendicular distance from the chord to the circle centre.


Do you have information on thickness calculations?

Within BSEN 1341 annexe A is a calculation to give guidance on the appropriate thickness and breaking loads for intended classes of use. Hardscape have a working understanding of this calculation and can, as required, give guidance.


Can you explain briefly what permeable paving is?

Permeable paving is a range of sustainable materials and techniques for permeable pavements with a base and Sub base that allow the movement of stormwater through the surface. In addition to reducing runoff, this effectively traps suspended solids and filters pollutants from the water.


What does a Corduroy and Lozenge look like?



Corduroy Hazard Warning - Higher Res


Buff Lozenge Platform Edge



Is there a formula to work out the number of setts in a tonne and flags on a load?


What are DDA regulations and steps?

The Building Regs part M require reasonable provision to be made for the access to a building and use of facilities within a building for disabled and less able bodied people, this also includes for the provision  of “markers” such as tactiles and visibility strips on stairways to enable clear and defined passage.

visibility strip


Is there a simplistic equation for working out the radius of a kerb?


What is a bull nose in relation to kerb or coping?

A bull nose is a radial detail to the leading edge:

Yellow Rock and Magma granite kerbs

What is a chamfered or splayed edge?

This is usually an angle cut to the leading edge of, for example, a kerb or coping piece:


If you find that there is something not covered here or would like further information about a particular subject covered then please fill  in the contact form at the foot and we will get back to you as quickly as we can.

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