The construction industry, like all industries, is awash with jargon and we thought it might be useful to put together another list of the most commonly misunderstood expressions and give our readers a quick explanation of what they refer to. This time around we are going to concrete on a few carpentry terms.
1.Staircase treads, risers and pitch.
Staircase treads and risers refer to the parts of the staircase that form the horizontal and vertical parts of each step. The tread is the horizontal section that your foot "treads" on each you climb the stairs and the riser is the vertical section at the back of each step. Some staircases will not have treads and therefore be referred to as an "open tread staircase."
Part K Building regulations stipulates that for domestic private stairs the tread (sometimes referred to as the "going") must be a minimum of 220mm deep and the riser must be a maximum of 220mm high. The risers and treads should also be consistent up a staircase as minor differences between steps can lead to falls.
Just to make things more complicated the pitch of the staircase is very important. This is the angle of the staircase when you take a line through the nosing of each tread from bottom to top. This angle cannot be over 42°. So even if you were to have a staircase with a 220mm tread and 220mm riser, the staircase would not meet Building Regulations as the pitch would be 45°.
The staircase stringer (sometimes shorted to "string") forms part of the structure of the staircase. It runs up both sides of a staircase and houses the treads and risers. Without a stringer the treads and risers would be floating without any support. It is possible to do away with the stringer entirely and have each tread supported by individual brackets hidden in the wall but let's leave that to another day!
In most houses, the question arises whether to have an cut string staircase or a closed string staircase. An cut string staircase is where the stringer is cut so that it follows the line of the treads and risers. This allows you to see into the staircase from the side and is a more traditional finish. It does however make cladding the stairs a very intricate task so it would be typical to have a full carpet or carpet runner on such stairs.
A closed string staircase closes off the sides of the staircase. It lends itself to having the treads and risers clad in timber flooring as there are less intricate cuts to make. It is also possible to mount a glass balustrade to the side of the stringer or to the top of the string so is a useful construction method when a modern finish is preferred.
Closed string staircase - BTL Property Ltd
Cut string staircase - BTL Property Ltd
3.Door lining, stop and leaf
The door lining is the first part of the door system that is fitted as part of the 1st fix carpentry. It is often built using a trenched door lining kit where the door liner head has pre-cut "trench" in it for either a 27 or 30 inch door leaf. The liner jambs are then fitted into the liner head and braced to ensure it is plumb and square within the stud or masonry wall that the door is passing through. When the wall is drylined and plastered the door lining should be flush with the skim. Some door liners have rebates in them that allow intumescent strips to be fixed into position. These strips in the event of a fire expand and create a seal between the door leaf and liner to prevent smoke passing through.
Next to be fitted is the door stop. The door stop quite literally stops the door so that it sits correctly in the door frame when closed and prevents the door swinging too far and potentially damaging the hinges. These are fitted inside of the lining and the position of these is dependent on the direction the door swings. When a non-fire rated door is upgraded to a fire rated door the door stop often needs to be replaced as a fire rated door is thicker at 44mm usually and therefore would sit proud of the door frame if the stops were not moved.
The door leaf is hung as part of the 2nd fix carpentry works with hinges routed or chiselled into the door lead and liner. Door knobs/handles, latches and strike plates are fitted to the door leaf. Most doors these days are FD30 rated (Fire Door 30 minutes) which means that they are manufactured and certified to be able to withstand 30 minutes of fire. FD30 doors are required between habitable rooms (kitchens, reception rooms and bedrooms) and the means of escape in a property ie the staircase and entrance hallway. FD20 and FD60 doors are also common. In the absence of a fire rated door protecting the means of escape it may be a requirement for a fire suppression system ie Sprinkler or Misting system. This is therefore quite common when an open plan basement or ground floor is designed to see sprinkler heads in the ceiling nowadays!
The final 2nd fix carpentry element is the fitting of the architrave. The architrave is a decorative element that hides the junction between the door liner and the skim plastered wall. Without architrave, this junction is liable to crack as the two materials expand/contract at differing rates as the house warms through. Where a less traditional finish is required it is possible to fit a "shadow gap" detail around the door and not have architrave.
4.Dado rails and picture rails
Yet more carpentry finishes. A dado rail is a timber moulding that is usually fitted at waist height in hallways and communal spaces and provides a decorative break between the lower and upper sections of a wall. It is often used where the lower section of wall has timber panelling or perhaps wallpaper but the upper section of the wall is painted or finished differently.
A picture rail is a very traditional feature that we don't see too often in refurbishments. This feature runs at high level around a room and was used to hand pictures, paintings and mirrors from. It is probably best to only consider this feature in a room with a high ceiling where a very traditional look is required. It can also provide a break between two different wall finishes.
Dado rail in the hallway - BTL Property Ltd
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