Oak frame staircase, connecting to an oak balcony

[AlanUK]

Hi all, 

 

I'm building an oak staircase going up to an external oak balcony.  On the balcony are two newel posts, that connect to the horizontal floor of the balcony via a cross lap joint.  You can see the notch cut in the post in the picture, which engages with a similar notch in the horizontal oak beam of the balcony.  It will thus be the only connection to the balcony.  The long notch below it is to receive the stringer for the staircase.

 

My question is how these should be fastened.  My builder assistant thinks that dowelling and glueing will be sufficient.  I am minded to use stainless steel threaded bar and nuts/washers. What would you people recommend?

 

Cheers.

 

Alan

[Oz07]

Are you happy with seeing the threaded bar and washers? Could you use some kind of coach screw from back of trimmer that the newel sits on into the back of the newel so not visible. 

[AlanUK]

A large screw is possible I guess.  I was intending to sink the nuts and washers into an enlarged hole, and cover with a dowel, so they wouldn't be visible.

 

[Oz07]

Not a bad idea but could be a big dowel. You could make the dowel look like a big square peg if you wanted i suppose?

[AlanUK]

Yes, something like that - it would hide the metalwork anyway,  And it seems like a stronger solution than using oak dowels and glue.

 

[Oz07]

Where do we stand with these design and fixing details? How much common sense can be employed nowadays before you have to involve an engineer?

[Alan Ambrose]

>>> My builder assistant thinks that dowelling and glueing will be sufficient.  I am minded to use stainless steel threaded bar and nuts/washers.

 

Traditionally a dowel or two only, no glue - say, 20mm. Huge oak buildings used to be built with nothing but woodwork joints and dowels. Taper it a bit so it's a tight fit when it's malleted in. From memory, you can do something clever with a slight oval so it pulls up even tighter as the oak dries out and shrinks (although that looks like dried oak already).

 

Or sure, biggish SS bolts, threaded rod, coach screws etc. A4 SS because oak is quite corrosive. Anything of the size that looks right (M10-M16 say) will be crazy over-specified for the shear load.

[AlanUK]

Yes, I have some 20mm dowels.  I was thinking of using 4,  but maybe that's over the top.  There aren't too many forces acting on it.  The main one will be the stringer, pushing the bottom in, but it's not a huge force.  And I guess if it does start to get wobbly I can always add a SS rod at a later date.

[joe90]

My stair kit came with torq screws and dowel type plugs, however I glued as well and good glue is as strong as the wood itself 🤷‍♂️

[ProDave]

I would do dowels and glue and coach screws from behind. That should cover all bases without spoiling it with visible fixings.

[AlanUK]

4 hours ago, Alan Ambrose said:

>>> My builder assistant thinks that dowelling and glueing will be sufficient.  I am minded to use stainless steel threaded bar and nuts/washers.

 

Traditionally a dowel or two only, no glue - say, 20mm. Huge oak buildings used to be built with nothing but woodwork joints and dowels. Taper it a bit so it's a tight fit when it's malleted in. From memory, you can do something clever with a slight oval so it pulls up even tighter as the oak dries out and shrinks (although that looks like dried oak already).

 

Or sure, biggish SS bolts, threaded rod, coach screws etc. A4 SS because oak is quite corrosive. Anything of the size that looks right (M10-M16 say) will be crazy over-specified for the shear load.

I like the idea of staying reasonably traditional, but might perhaps use some sort of bolt too, as suggested in a later post, and avoid the glue.  

You say it looks dry, and it does in the pic, but it's very very fresh - the wood was very damp when chiselling out the mortice, and it attacked my tools - I couldn't believe how much rust it caused in a day on my bullnose plane.

[joe90]

46 minutes ago, AlanUK said:

avoid the glue. 

Can I ask why?

[AlanUK]

 

17 hours ago, joe90 said:

Can I ask why?

I think it'll be hard to assemble (giving me limited time to actually put the parts of a complex and large assembly together), and make it impossible to disassemble should I want to, without causing major damage to the wood.