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September 15, 2010

What is the smallest spiral stair that complies with the Building Regulations

The various national Building Regulation Authorities for all of the UK and R.O.I. refer you to B.S. 5395 part 2 as being an acceptable standard for spiral stairs. Comply with that and you are OK. Therefore everyone in the spiral staircase game refers to that standard as the basis for design.

The smallest spiral stair permissible under B.S. 5395 is a spiral stair that has a clear width of 600mm. This is defined as a category A small private stair that is intended for use by a limited number of people e.g. an internal stair in a dwelling serving one room, that room cannot be a kitchen or a living room. So it is basically for one bedroom in a house. More than one bedroom and it has to be a bigger category B stair.

The problem with telling you what is the smallest diameter you can use as a category A spiral stair is the definition of 600mm clear width. This actually means the amount of space you have to walk up the stair without obstruction, and is measured as the distance from the inside of the handrail to the outside of the central column of the spiral stair. So if your hips are over 600mm wide either go on a diet or buy a bigger spiral stair. The radius of a 600mm clear width spiral stair will be 600mm plus the handrail (assuming the the handrail is on the outside edge of the spiral) and half of the centre column diameter. Multiply this by two and you have the overall diameter of an acceptable category A spiral stair. However the size of the centre column and the handrail will vary depending what material they are made of and other aesthetic factors so it is not possible to state a one size fits all diameter that will comply.

In practise you are not likely to find a spiral stair of less than 1400mm in diameter and more likely 1500mm in diameter that will comply with the width requirement of B.S.5395. Theoretically you could have a 1300mm diameter that would comply but it is certainly not available as a kit stair and would have to be a very slender design to comply.

The Stair Doctor

September 08, 2010

Which is better a round or a square aperture for a spiral stair.

It is really a matter of personal taste,there is no real structural differences either way, but there are several things to consider when cutting a hole in the upper floor to accommodate a spiral staircase.

First the hole has to be at least the same size as the diameter of the spiral stair plus ideally at least an extra 50mm to allow some clearance room on the outside of the spiral stair handrail as it passes through the opening.

Assuming that you have an upper floor constructed from timber joists and timber boarding, square holes are much easier to construct because you only have to trim the existing joist to form the aperture.

Round holes are far more difficult to construct because you have to first form a square hole, then make a threepenny bit shape (fifty pence shape if you are a baby) with offcuts of floor joists and finally form the circular opening with plywood or plasterboard.

The most difficult detail of a round aperture is to neatly finish the circular join between floor finish and vertical face of the aperture, not an easy problem to solve and a bespoke circular lipping can cost a fortune.

On the plus side round spiral stair openings look superb from both below and above, and a circular landing balustrade looks both good and is readily available with most spiral stair kits.

On the technical side round openings to spiral staircases allow for an infinite variation of stepping off points because you can rotate the whole stair anywhere through 360 degrees. A square aperture really restricts the stepping off points to just the centre of the four sides plus a few more options if you use a spiral stair with a trapezoidal landing detail (see earlier blogs covering this). This may not sound like much difference but it can mean everything if you are restricted in the access points to the spiral stair on either floor.

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The Staircase Doctor.

September 02, 2010

Can the Genius modular stair be used as a space saver stair.

Technically no, the Genius is a full tread staircase and it will take up about the same space as any typical house main staircase. With the exception of paddle shaped space saver stairs like the Karina all other stairs that are designed to comply with the Building Regulations will have very little room for movement as regards space saving. However the Genius modular staircase is adjustable in both height and length (rise and going) and this fact together with the option of a narrow 670mm tread width does mean that it is capable of squeezing into some fairly tight spaces and is therefore space saving. The down side is that it will not comply with the rise going and pitch requirements of any of the UK or ROI Regulations and it will be steep with a small tread going to stand on. That said it will look superb compared to a paddle shaped tread space saver stair.

It is not possible to give any specific footprint sizes that are achievable without knowing the floor-to-floor height and the stair layout that you require. As a guide the maximum tread rise of a Genius modular stair is 230mm and the minimum going is 190mm. This will produce the steepest (50 degrees pitch) and the shortest stair (approx 2350mm for a straight 13 riser stair). As always to get an accurate calculation on your specific stair you will need to consult a technical adviser with your details.

The Stair Doctor