TIMBER STAIRSA staircase with treads and risers constructedfrom timber boardsfrom timber boards.Timber stairs are comparatively light in weightand easy to constructand easy to construct.The timber used for the construction should befree from fungal decay and insect attack andfree from fungal decay and insect attack, andshould be well treated before use.Major limitation:Major limitation:Poor fire resistance ; fire resisting hard wood(such as teak oak mahogany etc ) of proper(such as teak, oak, mahogany etc.) of properthickness of about 45 mm may be used which issufficiently fire-proof.y p

COMPONENTS

The members of thestaircase flight are strings,g g ,treads and risers.

The strings are the supportg ppfor the stairs and act asinclined beam spanningbetween the floor and thelandinglanding.

The treads and risers arejoined to form the steps ofjoined to form the steps ofthe flight and are housed inor fixed to strings whosepurpose is to support them.p p pp

For additional support, a bearer or a carriage may be placedunder the treads (In normal practice, one bearer is provided for aunder the treads (In normal practice, one bearer is provided for a90 cm wide staircase, and an additional bearer for every 40 cm ofwidth.)

Timber Stairs

The members of the flight are usually cut from theg ytimbers of the following sizes:Treads 32 or 38, Risers 19 or 25, Strings 38 or 44.

Timber steps:

The thickness of timber step(tread) should not be lessthan 32 mm and that of riserthan 32 mm and that of riser25 mm.Timber tread and riser can besimply joined by tongue andsimply joined by tongue andgrooved joints. The joints arethen nailed or screwed.

•The nosing of the step should not project beyond the face of the riser for more than the thickness of the tread.•Scotia block may be provided to improve the appearance of the steps.•The small triangular wooden blocks, known as the glue blocks, may be provided at the inner angle formed between a tread and a riser, to giveprovided at the inner angle formed between a tread and a riser, to give additional strength to a wooden step. These blocks are glued and placed at about 80 mm distance.•A metal strip may be provided on the nosing of a wooden step to•A metal strip may be provided on the nosing of a wooden step to increase its resistance against wear and tear.

Joining risers to treads:

The usual method of joiningrisers to treads is to cut tongueson the edges of the risers and fitgthem to grooves cut in thetreads.

The tread of the stair tends tobend under the weight of peopleusing it.

When a tread bends the tongueon the bottom of the riser comesout of the groove in the treadout of the groove in the treadand the staircase ‘creaks’. Toprevent this it is a commonpractice to secure the treads topthe risers with screws.

Nosing on treads:Nosing on treads:The nosing on treads usually projects 32, or the thickness of the tread from the face of the riser below.

Angle blocks:After the treads and risers haveAfter the treads and risers havebeen put together and gluedand wedged into their housingsand wedged into their housingsin the string, angle blocks areglued in the internal anglesbetween the underside of treadsand risers and treads and risersand stringand string.

Angle blo k e t i ng lAngle blocks are triangularsections of softwood.

Their purpose is to strengthenthe right-angled joints betweenthe right angled joints betweentreads, risers and strings.

Winders:In narrow stairs, the treads of winder steps are supported on riserswhich act as cantilever beams fixed in the staircase wall. In suchwhich act as cantilever beams fixed in the staircase wall. In suchcases, the riser should be of sufficient thickness to perform thefunction of a cantilever beam. At its free end, the cantilever riserbeam is housed into the newel post. For wider stairs the winders arepsupported by means of bearers built into the wall at one end andframed and housed into the newels at the other. The back of thebarer is rendered flush with that of the riser immediately over it.y

Landings:A landing is constructed ofA landing is constructed oftongued and groovedboarding on timber joistswhich are supported on walls.

h f h lfIn the case of half spacelanding, a timber joist isplaced in the wall at one endand housed with the newel atand housed with the newel atthe other end.Half turn landing:A half turn landing isA half turn landing is

constructed with a sawnsoftwood trimmer whichsupports sawn softwoodl di j i t b dlanding joists or bearers andfloor boards.Newel posts:Th l t t fThe newel posts are cut from

100 X 100 timbers andnotched and bolted to thetimbertimber.

StringersSt ge sStringers are employed to provide support for the steps. Strings are inclined wooden members 32 to 50 mm thickStrings are inclined wooden members 32 to 50 mm thick and 25 to 38 cm deep. They are supported on newels, trimming joists or pitching pieces.g j p g p

The thickness of strings may be 3to5 cm and depth mayb b 2 0be between 25 to 40 cm.

St i b f f tStringers may be of four types:– Cut string

Housed string– Housed string– Rough string– Wreathed stringWreathed string

1) Cut String:) gIt is stringer with its upper surface having carriages or houses accuratelycut to receive the treads and risers and the lower edge being parallel tothe pitch of the stair. It is considered that the appearance of stair isimproved by use of cut-string, but it has the disadvantage of weakeningthe string as deep cuts have to be made in it.

2) Housed or closed string:string:It is a stringer having itstop and bottom edgesparallel to the slop of theparallel to the slop of thestair. It has grooves cuton its inside to receivethe treads and risers ofthe steps. The treads andrisers of the steps. Thetreads and risers areusually nailed, glued andwedged to the stringer.

Cut String Housed or closed stringg Housed or closed string

3) Rough String:R h t i i t d d i id t i f th fRough stringers are introduced in wider stairs for the purpose ofrendering intermediate support to the steps.

4) Wreathed string:It is curved or geometrical stair string It may be of cut or closedIt is curved or geometrical stair string. It may be of cut or closedtype.

Open Balustrade:Traditional balustrade consists of newel post, handrail and timber p ,balusters.Handrailthe top of the handrail is usually p yfixed at a minimum height of 840 vertically above the line of nosing for domestic stairs in a single house and 900 for all other stairshouse and 900 for all other stairs.Balustersthey may be 25 or 19 square or moulded They are either tenonedmoulded. They are either tenoned or housed in the underside of the handrail and tenoned in to the top of closed strings or set into o c osed s gs o se ohousings in the treads of flights with cut strings.

Closed balustrade:The space between the handrail and aclose string can be enclosed with timberclose string can be enclosed with timberpanels, plywood, hardboard, glass orany sheet material fixed to a lightframework.Spandrel:the triangular space between the

underside of the lower flight of a stairunderside of the lower flight of a stairand the floor is the spandrel.Carriage:A sawn softwood carriage is fixed belowA sawn softwood carriage is fixed belowflights of a staircase to give supportunder the centre of treads and also as afixing for plaster on the soffit orfixing for plaster on the soffit orunderside of flights.

Shaped bottom steps:For appearance sake the bottomstep of a flight of wood stairs isshaped as either a quarter or ahalf circle.

Open riser wood stair:An open riser or ladder stair consists of strings with treads and no risers so that there is a space between the treads. Open riser wood stairs are constructed as straight flight stairs between floors and there is no newel post to provide a fixing for the handrail.

METAL STAIRS

They are usually fabricated from steel andcast iron and their use is generallyg yrestricted to factories, godowns etc. In itssimplest form a metal stair consists ofsimplest form, a metal stair consists ofsteel stringer to which steel angles areriveted or welded and metal treads areriveted or welded and metal treads areprovided over them. Sometimes concreteis filled in steel grating to form the treads.

Th h th t d fi i t thThough they are strong and fire resistance, theymake sound when used by the users.Th l d f i l t iThey are commonly used for spiral stairs.Properly welded iron is one of the materials usedf b ildi t i Wh b ilt ith thfor building stairways. When built with thesematerials, stairways present light appearanceand their construction is carried out in aand their construction is carried out in arelatively fast manner, for which reason they arebuilt mainly for factories workshopsbuilt mainly for factories, workshops,warehouses and emergency exits.

Resting places are usually made of non-skid metal sheets or metallic gratesgallowing the passage of water and light.The railings of these stairways are alsoThe railings of these stairways are alsomade of metallic grates allowing thepassage of water and lightpassage of water and light.The railings of these stairways are alsog ymade of metallic materials.

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