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CONTENTS OF SITE QUESTIONNAIRERather than reproduce the questions in full, the following are abridged versions of those put to respondents.
Section A Users of stairs For answer by a main occupant of the house
1 Where do the loft stairs give access to?Identify rooms.
2 Who uses the loft stairs in your household?Sex, approximate age, frequency of use (1)(2)(3) and roomsused. (1) = Number/ day. (2) = Number/ week. (3) = Number/ month (Up and down = twice)
3 Do any of the users have a physical restriction? Eg walking difficulty, balance difficulty, generalweakness, poor co-ordination
4 Are there any members of the household who do not use the loft stairs?Sex, approximate age and reasonsfor non-use.
5 Are there any visitors who use the loft stairs?Response in same terms as question 2.
6 Are there any visitors to the house who do not use the loft stairs?Sex, approximate age and reason fornon-use.
If there was another adult in the household who used both main and loft stairs but experienced difficulties withone or other or both and who was available for interviewing, the remainder of the questionnaire was thenaddressed to that person.
Section B Personal details of respondent
7 When using main/ loft stairs, do you wear contact lenses?spectacles?
8 Do you have a fear of heights?
9 Do you ever feel dizzy?If yes, describe.
10 What is your height?
11 What is your shoe size?
Section C Respondent's performance on stairs The following questions referred to both the main and thep o w ell - will
16 Do you normally use the left handrail going up?going down?neither?
17 Do you normally use the right handrail going up?going down?neither?
18 Do you find the height of the handrail on the left to be too high?about right? too low?
19 Do you find the height of the handrail on the right to be too high?about right?too low?
20 Do you have difficulty in grasping and holding the left handrail going up?going down?
21 Do you have difficulty in grasping and holding the right handrail going up?going down?
22 Do you have to take any other precautions whilst using the stairs? If yes, describe, giving reasons. Eg notwearing footwear, not going barefooted or in stocking feet, facing backwards going down the stairs.
23 How easy do you find it to use the loft stairs compared to the main stairs?Loft stairs more difficult, loft stairsless difficult, both just as easy.
24 How do you find going up and going down the stairs?Down more difficult, up more difficult, same up and
down.
25 Is the top, middle, bottom or none of the stairs relatively more difficult when going up?when going down?
26 Do you find the loft stairs slower, the same or faster than the main stairs going up?going down?
27 Have you ever needed to hurry or run on the stairs?If yes, did you have any difficulty and describe the event.
28 Have you ever needed to turn round when going up the stairs (eg in an emergency) and if so did you have
difficulty? Give details.
29 Have you ever needed to turn round when going down the stairs and if so did you have difficulty?Givedetails.
30 Have you ever found the steps slippery?If yes, give details.
31 How do you find the steepness of the stairs?Steep, just right, shallow.
32 Have you had any other di fficulties whi lst using the stairs? If yes, give details.
33 Have you or any member of your household ever had an accident on the stairs?If yes, give details: time of day; type of accident (eg slip, tripping over clothes, carrying item); personal factors (eg illness or disability);conditions (eg dark, wet shoes). If fell, indicate whether up or down, point at which fall commenced, how manysteps in fall. Who treated injuries: yourself? GP?hospital? other?
38 Give details of any ways in which you feel the safety of the stairs could be improved.
39 If the loft stairs were already installed when you moved into the house, how long is it since you moved in?
40 If you had the loft stairs installed yourself, what was the date of the installation?
41 Have you made any alterations to the loft stairs?If yes, give details. Eg insertion or removal of handrails,carpeting etc.
42 If chi ldren use the loft stairs, how well do they manage to go up and down?
43 Were you given any instructions or warnings concerning the use of the loft stairs?
Section D Physical details of stairs The following questions referred to both the main and the loft stairs,and answers were sought for both
44 Draw a rough plan, with measurements, of the floor beneath the loft stairs and the location of the stairswithin the space.
45 Is the stairs design straight, dog leg, winder, spiral, curved or other? Describe the design.
46 Count the number of vertical risers.
47 Are the risers of the open or closed type?
48 What is the clear width of the treads of the loft stairs?
49 Measure from the front of the tread to the back of the tread on the longer side (see Figures 1 and 2).
50 Measure from the front of the tread to the back of the tread on the shorter side (see Figures 1 and 2).
51 Measure the projection of the shorter side of the tread beyond the longer side of a tread above it (see Figures1 and 2).
52 Measure the horizontal overlap of the tread on the tread below.
53 Measure from the surface of one tread to the surface of the tread above it (see Figure 2).
54 Measure the going of the main stairs (the going is the horizontal distance from the front of one nosing to thefront of the nosing of the stair above).
55 What is the tread covering?Eg wood, plastic, carpet, other.p o w ell - will
1 What is the model of the loft stairs and the name of its manufacturer?
2 Are your loft stairs straight? dog leg (turn sharply to left or right)?winder (curved)?spiral (stairs around acentral pillar)? other?
(a) Were they already installed when you moved in?(b) If yes, when did you move in?
(c) If no, how long have your stairs been installed (months)?
3 Have you made any alterations to your loft stairs? If yes, describe.
4 Do the stairs give access to main bedroom?guest bedroom?bathroom?office?sitting room?store room?other?(Tick more than one if necessary)
5 Give the main users of the loft stairs and the number of t imes a day the stairs are used. For each user:age, male/ female, and number of times a day used (Up and down = twice).
6 Is there anyone in the household who, for some reason, does not use the loft stairs?If yes, state who(referring to question 5) and explain the reason.
7 If you have regular visitors to the house who use the loft stairs, give age, male/ female.
8 Are there any visitors to the house who for some reason do not use the loft stairs?If yes, explain thereason.
9 Would you say that anyone has difficulty when going up your loft stairs?If yes, describe difficulty.
10 Would you say that anyone has difficulty when going down your loft stairs?I f yes, describe difficulty.
11 If the answer to question 9 is yes, which part of your loft stairs is considered to be relatively more difficultwhen going up?Top part, middle part, bottom part, none.
12 If the answer to question 10 is yes, which part of your loft stairs is considered to be relatively more difficult
when going down?Top part, middle part, bottom part, none.
13 Do any users have diff iculty in using the loft stairs when wearing long or restrictive clothing? Eg ankle-length tight skirt. If yes, state who (referring to answers to question 5).
14 Do any members of the household have difficulty carrying objects up or down the loft stairs?Eg vacuum cleaner tray of drinks load of washing If yes describep
19 When going up your loft stairs, could users turn round and go back down?Not at all, with difficulty, easily.
20 When going down your loft stairs, could users turn round and go back up?Not at all, with difficulty, easily.
21 How many steps are there in your stairs?
22 Are the risers open or closed?
23 Looking up the stairs on which side is the handrail? Left, right, both sides, neither.
24 For an adult, is the height of the handrail(s) too high?just right? too low?
25 For a child, is the height of the handrail(s) too high? just right? too low?
26 Do any of the users find the handrail difficult to grip? If yes, explain why. Eg the shape is unsatisfactory,there is inadequate space between the handrail and the wall.
27 When going up, do users normally use one handrail?both handrails?neither handrail?
28 When going down, do users normally use one handrail?both handrails?neither handrail?
29 What is the fill ing between the rail and the stairs?Eg vertical rails, sloping plank(s), solid, other.
30 Do you consider the tread surface of your loft stairs to be slippery?
31 What is the tread covering?Eg wood, plastic, carpet, other.
32 Do the stairs have protective nosings? If yes, describe.
33 Compared to your main stairs, are your loft stairs steep?just right?shallow?
34 Has anyone had an accident on your loft stairs?If yes state who and give details. Eg fell up or down, numberof steps missed. Were they carrying anything?Did they slip or tr ip? Was the lighting satisfactory? Did theyrequire treatment by a doctor or hospital?
35 Compared to your main stairs, how safe do you feel on your loft stairs?Less safe, just as safe, more safe.
36 Are there any ways in which you feel the safety of the loft stairs could be improved?
37 What is the type of dwelling?House, bungalow, other.
APPENDIX CALTERATIONS AND SUGGESTED IMPROVEMENTS TO LOFT STAIRS
Alterations25 respondents (17% of the total) had carried out the following alterations to their loft stairs:
added a handrail (6)tightened the bolts to make them more secure (3)removed a handrail (2)
lowered a handrail (2)carpeted the treads (2)fitted non-slip strips to the treads (2)removed backing boards to give more space on the treads for users' feet (2)people claimed to have had a platform built at the bottom of the stairs to make them less steep (2)reduced the gap between the handrail and the adjacent wall to make the stairs slightly wider (1)moved the stairs sideways to give more space to hold the handrail (1)changed the handrail from round to a sloping plank (1)added a backing board so that items could not be dropped through (1)
Suggested improvements79 respondents (52% of the total) thought the following improvements could be made (some respondents offeredmore than one suggestion):
fixing a non-slip surface to the treads (31). Specific suggestions made were:nosing strip (14)non-slip surface (10)carpeting (8)
making the pitch of the stairs less steep (21); though respondents were aware that this would take upmore space, they had chosen or were forced to install a steep design of stairs because of lack of space
providing always for two handrails (13); some respondents pointed out that the width of the stairs would stillhave to be adequate
fixing a backing board to the open risers (9)changing to a full conventional tread (4)making the stairs more stable (4); some rocked slightly when ascended or descendedshaping handrails so that they are easily gripped (2); ie round like a mop handlefitting more secure handrails (2)designing stairs that have a quarter or half turn landing, or a winder to make users concentrate and be less likely
to fall (2)designing stairs to be wider (2)designing stairs with deeper treads (1)fixing treads more securely (1)reducing the height of rises (1)
APPENDIX DCOMMENTS ON DIFFICULTIES AND PRECAUTIONS ON LOFT STAIRS
Difficulties in using loft stairs23 respondents (15% of the total) reported that someone in their household did not use the loft stairs for thefollowing reasons:
too young (12)handicapped (5)
over 70 years old and had difficulty using the stairs (3)children were not allowed in their parents' or siblings' bedroom (2)no reason (1)
7 respondents reported that some people (particularly visitors) had difficulty using the stairs the first few timesor because they did not use them often
Clothing37 respondents (31% of the total) reported that they experienced difficulties using the main stairs and 53 (35%)
when using the loft stairs wearing certain clothing (eg a long dressing gown or tight skirt)
Carrying objects105 respondents (70% of the total) reported experiencing difficulty carrying objects up and down the loft stairscompared to 5 (site sample only) on the main stairs. These included the following reasons (some respondentsreported more than one difficulty):
when the object was a vacuum cleaner (33)carrying anything which required two hands (24)
carrying bulky objects (13)needing to hold one handrail (12)when the object was a tray of drinks (7)when the object was a suitcase, partly because of the width (4)when carrying items down it was not possible to see the steps (4)carrying any items on the stairs (3)carrying objects up the stairs because the stairs were excessively steep and they were not able to see
where to put their feet (2)when carrying items that put them off balance (1)carrying items on narrow stairs (1)carrying a child (1)no reason (3)
Precautions97 respondents (64% of the total) stated that they would take precautions with the type of footwear they would
41 respondents reported accidents on their loft stairs.
What happened on loft stairsslipped (25)missed their footing (5)tripped (2)
no description (9)
Number of steps fallen on loft stairs37 people fell when going down the stairs:
fell 7 steps or more (8)fell 2 to 6 steps (27)fell one step, or slipped but did not fall down any steps (6)
4 people fell when going up the stairs
Contributory factors with loft stairsvictims were in stockinged feet (11)stairs had been polished just prior to the accident (2)victims were carrying items (2); one a quilt and one a vacuum cleanervictim turned round (1)victim heard the telephone ring (1)victim was not concentrating (1)
victim did not position feet properly (1)victim had flu (1)victim was pregnant (1)no contributory factor cited (20)
Outcome of accidents on loft stairstreated at home (10)went to hospital for a checkup, but nothing serious reported (2)did not require any treatment (29)
18 respondents reported accidents on their main stairs.
Contributory factors with main stairsvictims were in stockinged feet (2)
victims were rushing (2)victim was wearing slippers (1)victim was wearing wrong footwear (1)victim heard the telephone ring (1)victim tried to pick up an object (1)no contributory factor cited (10)
Outcome of accidents on main stairstreated at home (3)went to hospital for a checkup (2)did not require any treatment (13)
APPENDIX FSPECIFICATION OF THE GEOMETRY OF ALTERNATING TREAD STAIRS
by G M B Webber
IntroductionThere is no existing British Standard specification for alternating tread stairs within the UK nor has theirgeometry been described. Therefore a general description of the geometry of alternating tread stairs wasdeveloped in order to categorise the types of stairs encountered in the survey.
Designs with straight flights and flights with quarter or half turn landings are considered. The geometry of spiral stairs designs and stairs with winders has been excluded due to their complexity.
In Germany these stairs have been referred to under Accident Prevention Regulations ZH 1/ 26210 since 1973,
and a specification has been introduced into the USA in the Life Safety Code9. These two specifications refer totwo different types of design of alternating tread stairs and, furthermore, refer to different designs to those beingintroduced into the UK. These other specifications are presented in more detail in Appendix H for referencepurposes.
The aim was to develop calculation methods which provide a systematic means of assessing the dimensionalcharacteristics of a wide range of manufactured alternating tread stairs. Thence to provide a means of sett ingrequirements, aiding the design of stairs and the checking of plans and related details. Equations have beendeveloped to calculate rise, going, pitch, length of stairs with straight flights, and quarter or half turn stairs.
DefinitionsThe type of shape of tread found in the survey is shown in Figure 1.
The following notation is used to define and calculate the dimensional characteristics of alternating tread stairs:
T 1 is the depth of tread; ie measured from the front of the tread to the back of the tread on the
longer side (in mm)T 2 is the depth of tread on the shorter side (in mm)
P is the horizontal projection of the nosing of the shorter side of a tread beyond the nosing of the longerside of the tread above it (in mm) as shown in Figures 1 and 2. P can have a positive value (nosing
protrudes) or negative (nosing retracted)
K is the horizontal distance (in mm) as shown in Figure 2G is the going (in mm) as shown in Figure 2. G has been defined in this manner to most closely
resemble the traditional use of the term 'going' but also takes into account which of the two (or both)nosings above project the foremost into the vertical plane to obstruct the lowering of a foot
Q is the going (in mm) of the first tread below the top landing in Design C as shown in Figure 2cθ is the pitch (in degrees)
Design of straight flight stairsThe site survey revealed three basic types of design of stairs characterised by the projection of the nosing of the
intermediate tread (shorter side) P . The stairs are classified as follows:
Design A: P is positiveDesign B: P is zeroDesign C: P is negative
The geometrical description of these three types of design are presented in turn below.
Design A
In this design the constructional arrangement of the treads, shown in Figure 2a, is such that the nosing of theshorter side of an intermediate tread projects horizontally beyond the nosing of the longer side of the treadabove it; ie P is positive.
In Figure 2a, the three marked goings G are equal.
In this constructional arrangement:
K =
T 1 –
T 2 +
P (1)
G = 2K – P (2)
G = 2(T 1 – T 2) + P (3)
tan θ = r (4) --------
K
G + P = 2r (5) ----------------
tan θ
It is possible for G to be longer than the depth of tread T 1 thereby creating a horizontal gap. This should be
avoided, so that for G to be always equal to or less than T 1:
D = (N – 1)r + T 1 (12) ---------------------------
tan θ
tan θ = (N – 1)r (13) ---------------------------
D – T 1
Clear headroom H is measured from the pitchline as shown in Figure 3.
The above equations are used to calculate the dimensional characteristics of a manufactured alternating tread
stairs consisting of a single straight flight (see Appendix G). The calculated dimensions agree very closely withthe manufacturer's li terature. Where P is positive, the designs are of type A.
Design BIn this design the constructional arrangement of the treads, shown in Figure 2b, is such that the nosing of theshorter side of an intermediate tread vertically aligns with the nosing of the longer side of the tread above it; ieP is zero.
In Figure 2b, the three marked goings G are equal.
In this constructional arrangement:
K = T 1 – T 2 (14)
G = 2K (15)
G = 2(T 1 – T 2) (16)
tan θ = r (17) --------
K
G = 2r (18) ----------------
tan θ
In order to avoid a horizontal gap, such that G ≤ T 1, the following conditions should apply:
Since P is negative, this means that Q > G as shown in Figure 2c:
tan θ = r (25) --------
K
G = 2r (26) ----------------
tan θ
Assuming that the top tread abuts the top landing, then equations (8) to (13) also apply to this design.
The above equations are used to calculate dimensions presented in Appendix G. Where P is negative, the designis of type C.
The type of construction of the manufactured stairs detailed in Appendix G uses a fixed length of mainsupporting string and cams on each tread enable treads to be levelled. With this type of construction, the lowestpitch will have maximum projection and, as the pitch is increased the treads overlap more, the projection passesthrough zero and onto a negative value. Hence for example in Appendix G for 13 treads, when K changes from
134 mm to 89 mm, a shift of 45 mm, P changes from 24 mm to –21 mm, a shift of 45 mm.
Design of quarter turn stairsQuarter turn alternating tread stairs are available and the survey included this type of design. In the examplewhich follows, an intermediate landing is fixed against the walls at a 90° turn. Additional notation is required
and a similar notation to that used for quarter turn winder stairs in BS 585:Part 112 is used here. Additionaldefinitions are:
N 1
is the number of alternating treads in lower straight flight
N 2 is the number of alternating treads in upper straight flight
a for the upper straight flight is the horizontal distance from top landing (back edge of top tread) to frontedge of bottom nosing (in mm)
b for the lower straight flight is the horizontal distance from the intermediate landing (rearmost frontedge of landing profile) to front edge of bottom nosing (in mm)i h h i l di f l di (b k d f d) ll (i ) h i Fip
r = H (31) ---------------------------------------------
N 1 + N 2 + 1
These equations, together with equations(1) to (5) when P is positive, and equations (21) to (26) when P isnegative, are used to calculate the space required for a range of quarter turn stairs; ie distances A and B (seeAppendix G). The calculated values are generally within a mm or so of the manufacturer's tabulated data.
Design of half turn stairsHalf turn alternating tread stairs are available and the survey included this type of design. In this example, an
intermediate landing is fixed against the walls at a 180° turn. The following definitions and notation are used:
N 1 is the number of alternating treads in lower straight flight
N 2 is the number of alternating treads in upper straight flight
a for the upper straight flight is the horizontal distance from top landing (back edge of top tread) to frontedge of bottom nosing (in mm)
b for the lower straight flight is the horizontal distance from the intermediate landing (rearmost frontedge of landing profile) to front edge of bottom nosing (in mm)
A is the horizontal distance from top landing (back edge of top tread) to wall (in mm) as shown inFigure F2B is the horizontal distance from bottom tread (foremost front edged) to wall (in mm) as shown in
Figure F2L a is the length of the intermediate landing from the wall to the foremost front edge of the bottom nosing
of the upper flight (in mm) as shown in Figure F2L b is the length of the intermediate landing from the wall to the rearmost front edge of the intermediate
landing (in mm) as shown in Figure F2C is the length of the intermediate landing (in mm) as shown in Figure F2
It can be seen that:
A = L a + a (32)
where a = (N 2 – 1)K + T 1 (33)
B = L b + b (34)
where b = (N 1 + 1)K (35)
r = H (36) ---------------------------------------------
N 1 + N 2 + 1
These equations, together with equations (1) to (5) when P is positive, are used to calculate the space requiredfor a range of half turn stairs; ie distances A and B (see Appendix G).
Stairs a L a b L b A B classification* (mm) (mm) (mm) (mm) (mm) (mm)_______________________________________________________________________________________________________________________________________________
Stairs a L a b L b A B classification* (mm) (mm) (mm) (mm) (mm) (mm)_______________________________________________________________________________________________________________________________________________
* The first figure gives the number of treads on the lower straight flight. The letter L' indicates a 180° turnlanding. The last figure gives the number of treads on the upper straight flight.
German recommendationsA German Code of Practice, ZH 1/ 26210, under Accident Prevention Regulations, exists for stairs withalternating treads. The Code states that this type of stairs is an emergency solution which should be used onlywhen the space problem allows no other solution. Suggested suitable uses are for cellar manhole stairs or forservice stairs in boiler houses and machine rooms.
For straight flights, step widths of 450 mm to 500 mm are said to be suitable. If the space available is wider, thegap between wall and stairs edge must be sealed. This type of stairway does not allow users to pass one another.
The Code indicates that this type of stairs can be built in wood, steel, stone or concrete.
The type of tread design recommended in the Code is shown in Figure H1. The following notation is used forthis example:
N is the number of treads (in this report the shaped upper platform is not counted as a tread)
D (for a single straight flight) is the horizontal distance from top landing (back edge of top tread) to frontedge of bottom nosing (in mm)h is the floor-to-floor height (in mm)G c is the going along the centre line of the width as shown in Figure H 1
G w is the going along the line w—w as shown in Figure H 1
In order to get an indication of the dimensional limits set by the Code, take an 11 tread stairs with a 250 mmrise. This would give:
h = 3000 mmN = 11r = 250 mm
Using equations (38), and (40) to (42):
G c = 111.2 mm
G w
= 222.4 mm
θ = 66.0°
Hence in this example D is 0.46h .
The above example indicates limits of maximum rise of 250 mm, minimum going on line w—w of 222 mm, and amaximum pitch of 66°.
USA recommendations
In the USA, these stairs were referred to for the first time in the National Fire Protection Association NFPA 101Life Safety Code 19889. The Code says that alternating tread devices may only be used for access to unoccupiedroof spaces or as a secondary means of escape from storage elevators; also towers and elevated platforms aroundmachinery and boiler rooms subject to occupancy only by not more than three able-bodied adults. Thealternating tread stairs design differs in having three strings, one along the centre of the stairs width whichseparates the user's feet and the other two at the sides. Each tread is only 'half-width'.
The requirements are:
(i) The occupant load served shall not be more than three(ii ) The rise shall not exceed 203 mm(ii i) Treads shall have a minimum projected tread depth (equivalent to going in this report) of 229 mm with
each tread providing 267 mm of depth including overlap(iv) The initial t read of the stairs shall begin at the same elevation as the platform, landing or floor surface(v) The alternating treads shall not be laterally separated by more than 50 mm(vi) Handrails shall be provided on both sides of the stairs(vii) The clear width between handrails shall be a minimum of 432 mm and shall not exceed 610 mm(vi ii ) A minimum distance of 152 mm shall be provided between the stairs handrail and any other object(ix) Headroom shall not be less than 2030 mm
Requirement (iv) relates to the central string. Requirement (vii) is to allow easier carrying of small objectsoutside the handrail.
Requirements (ii) maximum rise of 203 mm and (iii) minimum going of 229 mm lead to a limit on maximump o w ell - wil
Table 11Dimensions of main stairs _____________________________________________________________________________________________________________________________________
Case Number Overlap Going Rise Pitch Pitchno. of risers calc. meas.
Table 11Dimensions of main stairs (cont) _____________________________________________________________________________________________________________________________________
Case Number Overlap Going Rise Pitch Pitchno. of risers calc. meas.
Table 17Projection on loft stairs (site sample only)
Projection (mm) Number %
45 to 54.9 1 135 to 44.9 1 125 to 34.9 1 115 to 24.9 10 105 to 14.9 27 280.1 to 4.9 5 50 27 28
–0.1 to –4.9 5 5–5 to –14.9 13 13–15 to –24.9 5 5–25 to –34.9 1 1–35 to –44.9 1 1–45 to –54.9 1 1
Total 98 100
Table 18Dimensional characteristics of survey stairs Designs A, B and C
Characteristic Design A Design B Design C
Depth-long (mm) 215 to 270 225 to 265 220 to 265Depth-short (mm) 115 to 164 110 to 155 110 to 155Projection (mm) 2 to 47 0 –2 to –48Going (mm) 191 to 267 200 to 250 146 to 240Rise (mm) 185 to 235 193 to 230 197 to 222Calculated pitch (°) 54.3 to 64.1 58.0 to 63.4 59.5 to 71.8Sizes of gaps (mm) 10, 12 4, 5, 10, 10
(number) (%)Extends beyond top and bottomsteps 10 11 60 38Extends beyond top step but endsbefore bottom 28 31 53 33Ends before bottom and top steps 47 52 26 16Extends beyond bottom step butends before top 2 2 14 9
Not known/ no handrail 3 3 6 4Total 90 100 159 100