Bi-fold doors - best construction?

[Helvetica]

Hi lads, we are fitting bifold doors to a new extension. They are 2.7m tall and the span is 3.5m. The original spec from the architect is for mahogany, but I have concerns over movement, leading to loss of insulation. I'm asking them to research Accoya, and aluclad.

Would any of you have experience with Accoya? Does it live up to the sales pitch? Is it too new to tell?

I understand Alu clad would be zero maintenance, I don't mind maintaining timber doors, but like I said my main concern is movement, longevity and insulation. What would you think is the best material choice here?

Thanks

 

[Bradshaw Joinery]

Accoya is fantastic stuff and will not dissapoint. Main points are non corrosive fittings, stain blocking primer and only pu glue or aliphatic resin... Pu is much better though.

Incorporate v grooves in all perpendicular joints with appropriate v groove sealant ans your paint should last a very long time before needing redoing.

 

[RobinBHM]

Accoya is certainly the most stable material, much more so than sapele.

A 3500mm bifold probably has 4 doors, so that equals 8 stiles with a movement of potentially 1mm or more each, so a possible total variation of 8mm which is quite a bit. I have to say though that Ive made plenty of bifolds in both iroko and oak without any problems in service. Since the availability of accoya I now would choose to use that.

V grooves at joints is very good advice, it is impossible to stop movement at that point, especially on a bottom rail. The expansion of the bottom rail slightly fractures the paint line allowing moisture ingress long term.

The frame may still be in normal timber and actually the saving in time for using accoya on door leaves actually means there is not a great cost implication.

 

[Helvetica]

Great info, thanks lads. Going with Accoya for the bifold