Shows that the design is based for child safety. You have to insert a safety-riser into the stair design under each tread in order to make sure that a small child or infant can not get it's head through the opening between each tread. It is used as an interior design to allow for light to pass through under the stair case. For exterior use, the open riser allows air, snow, leaves, etc. to pass through, eliminating a build-up of debris under the steps. The Open Riser Type 1 Stairs is structurally supported by that portion of the reverse-horse stringer that sits below the bottom of the tread line and is perpendicular to a level line (equal with the floor line) that the stringers rest upon. An example of this can be seen in the diagram below.
The Closed Riser Type 2 Stairs
This stair type is exactly the same as the open-raiser except the raisers run all the way up and down between the treads. This is mostly used for interior purpose and can be used between two walls. The Type 2 can be free standing from a structural point of view and sit in an open space leading from one floor to the next. The diagram below illustrates all of the pertinent construction information for this stair type.
This is bit more structurally sound than the Type 1 due to the fact that the risers can be glued and nailed (or screwed) to the tread material forming a diaphragm in folded-plate format from the top through the bottom of the stringers. This form ads a certain degree of rigidity to the entire unit if the treads. The treads, risers, and stringers act as one unit under these circumstances and can be of great benefit if the stair unit sits in an open space and has no side-walls. The risers actually become part of the structural beam in that case — if the assembly of gluing and nailing is executed properly.
The Wedge and Glue Type 3 Stairs
From a structural point of view, this stair type is the best due to it's standpoint of wear, durability, and structural integrity. They are designed to sit between two walls and deliver the stair loads of the tread-riser uni-body to those walls. They will accommodate heavy foot traffic and people who are carrying maximum loads.
The stringers for the Type 3 stair types remain the full width (11-1/4") of the 2 x 12 material and the treads and risers are routed into them about 1/2" deep using a template that outlines the tread, riser, and the wood-wedge space below them that is out of sight when the stair is finished. The stringers are screwed to the side-walls and then the treads and risers are inserted in a methodical manner starting and the bottom and working your way to the top.
As the assembly proceeds one step at a time, the area below the treads and risers that are routed out for the wood-wedges, are liberally painted with wood-glue and the wedges are driven into the wet-glue. The risers are glued into each tread-bottom as can be seen in the diagram. For maximum control of warping and twisting, each tread has it's grain broken on the underside by saw-kerfing them in a table saw.
Sound proofing stairs
Walls and floors should have a minimum airborne insulation value and the floors and landings a maximum impact noise level. For new build these are 45dB for airborne and 62dB for impact and for buildings the subject of a change of use they are 43dB for airborne noise and 64dB for impact noise.
1. Screw Acoustic Plasterboard to the underside of the stairs.
2. Fix timber stud to the Acoustic Plasterboard and infill with the correct thickness of Acoustic Mineral Wool.
3. Screw to the stud a double thickness of 15mm Acoustic Plasterboard to finish off .
4. Stairs that have been constructed with the underside inside another flat should also be boxed in with a cupboard clad with a double thickness of Acoustic Plasterboard and fitted with a small, well fitted door for access.
By Sonal Mistry
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