Spindle fitting introduction.
The spindles are traditionally housed into the treads, this is best done during the manufacturing stage; as this will allow for fixing of the treads through the base of the spindle housing and avoid hitting screws when fitting as an afterthought on site. This also eliminates the possibility of the screws being outside of the spindle area and pellets being used to cover the screw heads. When the stairs are for painting this is not so much of an issue but with many staircases having natural finished treads this is not desirable; as the pellets will more than likely be visible after polishing.
The spindle position would traditionally be set once the handrail flow has been calculated, from the handrail the centre line can be used to array the spindles, from this the riser and stringer face positions are determined.
The top of the spindle is fitted in one of two ways.
Square top spindles.
The first which is normally used for spindles with a square top, is to pair the top face of the spindle to the underside of the handrail, this aids with a full contact glue face between the spindle and the handrail, this would then be fixed in place with a cut nail, with modern tools this is just as easy to do with a pilot hole countersunk and a screw applied.
When the spindles are housed in such a way, that they may only be set in position from the side of the tread without the nosing being fitted, then the nosing is not normally glued into place, this will facilitate removal of the nosing should the spindle require being replaced. in this situation it is good practice to have the end of the tread and the return nosing rebated and a tongue set in the rebate to keep the nosing in position.
Round or turned top to the spindles.
These would normally have a hole drilled into the underside of the handrail, the top of the spindle would be glued into the hole with a cut nail used to secure it in place and prevent the handrail from lifting clear of its locating hole.
Housing the spindles into treads.
A modern way.
This is one way to fit the spindles using a router rather than saws and chisels, this locks the spindles down nicely and prevents movement. This can only be carried out with the landing or tread return nosings removed.
By using this method each spindle will stand upright and not require any mechanical fixing to be used.
When done with a router and jig, the housing can be machined in as quickly as chopping a square housing.
When set correctly the spindle is pulled down onto the tread surface and thus not leaving any gaps. this method only works for new flights when the treads are clean and level.
The only addition in time is running the base of the spindles past the dovetail cutter and making the jig but if making a jig for the router anyway to cut square pockets there is no difference in time.
Only three faces require dovetailing as the face that faces the nosing will be left square.
This method works very well when using turned top spindles; as you can stand all the spindles in place easily and lower the handrail down onto the tops of the spindles.
A historic way.
On some historic stairs, the spindles would have been dovetailed through the thickness of the tread, the spindle pushed in from the return nosing end of the tread, spiked into place with a cut nail or brad and then the return nosing fitted to conceal the workings and fixings.
This method would have been used mainly on the larger high quality staircases.
Here we show how this would be achieved on a straight flyer section when the stairs have tread brackets set on the stringers.
In the 3D model we have left the layer control on, this will allow you to turn off different layers to see how the treads, stringers, spindles and risers all interact with each other.
These pictures show this detail on an old staircase was being renovated, the first picture shows the end of the treads with the tread nosing mitre, return nosings and tread brackets removed, here you can see the dovetail detail. The seats have been damaged over the years but you can see where they should be.
The second picture shows the upper part of the flight with the return nosings and brackets still in situ.
This method I have come across on many late 19th and early 20th century manufactured staircases.
The spindle would be set with the front half the spindle chopped through the tread and the rear half only rebated in to a depth of about a 1/2″ deep and then fixed with a cut nail and glue to secure it in place.
This method creates a very stable spindle socket and gives good lateral rigidity to the handrail in the longer straight sections of stairs.
This method I have come across and used myself a few times, the reason I have used this method is when removing a standard 7/8″ or 22mm spindle that has been housed through the tread and replacing it with a larger spindle.
Rather than plugging the square socket left by the original spindle and then chopping in a square socket, by widening the existing socket and then rebating the remaining area under the new spindle there is a considerable increase in the strength of the spindle seat.
Square seat, morticed through.
Traditional 7/8″ spindle.
This is another traditional way of cutting the spindle seat, this method was used when the straight spindle was to be used.
The standard size for these spindles is 7/8″ 22mm square, this may have been swapped for a 7/8″ X 5/8″ 22mm X 16mm spindle to give the spindle a wider look, the 7/8″ 22mm would run across the riser face and the 5/8″ 16mm face would run over the stringer face.
The mortice for these would run through the depth of the tread and more often than not the spindles would be pinned through the side before the return nosings were applied.
In later years many of these spindles have been replaced with larger turned spindles, this is generally achieved by removing the existing spindle and increasing the mortice to the width of the new spindle and rebating the rest of the spindle base in by about 1/2″ 12mm deep, this creates a half lapped joint and gives a secure seat for the new spindle.
Suited to existing flights.
When the stairs have the nosing already fitted, the spindles can be housed in with a blind mortice. This does not have the strength or stability of the dovetailed housing but still gives a good fixing.
This works for existing flights where the treads have settled over time and may not be 100% flat or level; allowing the spindle to be off perpendicular to the treads but still keeping a tight fit around the base of the spindle.
This is done by marking around the edge of the spindle and chopping or rebating out the tread to between 1/2″ 12mm to 3/4″ 19mm deep.
When the return nosing is already fitted this is the optimal depth, this will allow you to tip the spindle into the hole but also give enough strength to hold the handrail steady.
This depth should still leave enough material under the spindle for the tread to be fixed down to the cut string.
When chopping the hole it is best to undercut the sides of the rebate, then chamfer the bottom of the spindle before pushing it home, this has two benefits.
- The sides of the rebate will have some play in them to squash around the spindle and close any gaps at the surface of the tread, keeping it clean for polishing. You will need less chamfer with the grain than on the end grain sides of the rebate.
- There is some room for the glue to sit in.
the angles need to be very gentle and the chamfer to the bottom of the spindle, must not be greater than the depth of the rebate.
On straight flights without newels handrail ties are recommended.
Side mounted spindles.
Cut into return nosing.
When the spindles are set on the ends of the treads and outside the stringer area,
The back face or staircase side of the spindle is normally set against the front face of the scotia moulding,
The bottom of the spindles will have a finial fitted to them and in most instances will be cut to follow the pitch of the stairs, keeping a constant border dimension between the bottom of stringer and the bottom of the finial.
occasionally the spindles are cut to follow the tread line. They will still have the finials fitted to their bottoms.
Rebated stringer, cast baluster.
When getting cast balusters made, create the bottom block before sending for casting.
Any 90º bends should be filleted to create a webbing, this will avoid casting faults that may crack.
In the visuals, for descriptive purposes, we have shown the cutouts at each tread, these would normally be spaced at around every 6 treads.
Extended baluster bottom rebated into the stringer face.
This is a method used for adding rigidity to long straight flights and landings, These are normally placed about 6 treads apart.
Using cast balusters will also help on handrails that require stabilising but handrail ties are not desirable or would have to be extreme in length.
Set behind tread brackets.
The cast baluster has a rebate to accept the tread bracket and the stringer is rebated to accept the remaining thickness of the baluster foot, the baluster is then fixed with screws into the side of the stringer and covered with the tread bracket.
There will be a timber block set inside the stringer to give extra support when screwing through the stringer.
Without tread brackets.
The baluster is cast in the same way as for the above procedure but is set with the face of the spindle aligned as it would be normally over the stringer face, the tread bracket rebate is then covered back over with a piece of timber ready for painting.
Cranked or kneed bottom block.
The cast baluster may also be cast with a cranked bottom block, the cranked base to the block is set under the tread and fixed from inside the stringer.
This style of fixing will work with or without tread brackets as it can be rebated into the stringer if required to bring it farther over the external stringer face.
These again would be cast from a turned spindle with the cranked section fitted to the spindle before casting.
The balusters may be fitted to the stringers in advance of the treads being fitted. when the balusters are fitted on site after the stairs have been installed, then a pocket in the tread is required and a packing block is used to patch the tread back in after the baluster has been installed.
These balusters are positioned mid tread as when fitted to the front of the tread they would protrude through the front of the riser.
Cast balusters into stone treads.
When seating cast balusters into stone treads, the traditional method is to drill a hole larger than the spigot on the bottom of the baluster.
Set a clay retaining wall around the drilled hole to retain any overflow and to funnel the lead into the hole.
Set the spindle in place and fill the hole with molten lead, being careful not to overfill the hole. By caulking the baluster in this way, should the baluster become loose over time, the lead may be tamped down to lock the baluster back into place and make it secure once more.
With stone stairs, the balusters are set further away from the edge of the stairs than on timber flights.
With modern day adhesives the use of chemical anchor fixing is being used, as to how long this will last or whether it will be able to be reaired as easy as lead only time will tell.
For illustration purposes, I have just used a small section to represent the baluster foot.
Housing the spindles into a stringer capping.
Square spindle base, into a stringer capping.
When setting the spindles into a stringer capping, the rebate will require the sides of the rebates to be vertical and at the staircase pitch to the capping.
The spindle base will not require chopping in as deep as it would when fitted directly to the treads and 1/4″ – 6mm to 1/2″ – 12mm will suffice.
Once again as with the square chopped rebate into the cut string tread surface, it is best to undercut the rebate and chamfer the base of the spindle.
Although the spindle base is set into the rebate, it is still good practice to get the pitch angle cut correctly; as the glue face is where the strength is and relying on the glue around the outside of the rebate is not ideal
The spindles will not be as long as when fitted to the treads and the newel posts will restrain much of the lateral movement from the handrail. Therefore the spindle is more or less just fall protection and not so much structural.
Square spindle base, into a stringer capping with infill fillets.
In recent years or at least since around the late 20th century as in 1970’s to 80’s I have noticed stringer cappings being made and used with a groove rebated along the length of the capping and an infill fillet supplied, the spindles are fitted into place and fillets set between them to lock them in.
The spindles will still have to be cut to the correct angle and length for the glue faces to have contact, this procedure will also mean sanding or pairing the top face of the fillet piece to the top of the capping.
The advantage of this system is that if the spindle is fitted in the wrong place it can easily be repositioned and a new fillet cut in.
This may be suitable for painted finishes but will show the difference in grain if used on a natural timber finish.
This style of capping may also be used on the landing nosing, in this instance, it is fixed down over the landing nosing and may be used to cover the original spindle seats when the spindles are replaced.
Still working on top fixing:
Square spindle top.
Turned spindle top.
Metal spindle with core rail set over.
Metal spindle without core rail.
Spindle position. For cut string stairs.
Calculate spindle spacing on closed string stairs.
Just a quick video I have put together.
This is a very quick over view of how the spindle spacing may be calculated for closed string stairs.