Constructing an insulated door

[theflyingpig]

I need to make a custom sized insulated door to fit at the bottom of some loft stairs. I'm thinking to sandwich 25mm celotex between two skins of sheet material, with frame built of PAR machined down to 25mm...

My question... Would I be better using ply, or mdf for the 'skins'?
Thanks for any input!

 

[foxhole]

18mm mdf for face with insulation behind then thin sheet of ply or mdf , screw thru from rear which helps fix insulation ( glue as well).

 

[robinbanks]

You can buy this already done, if you look at SIPs, for glueing it up yourself, expanding foam does a great job as an adhesive, but don't apply the sheet immediately after it's squirted out of the can - let it sit a bit first to go gooey/tacky and acquire some structure otherwise it'll just collapse. It's also possible to get two part foams that form PIR when mixed, if you want to mix it up yourself, pour it into a mould that is holding both sheet sides and let it expand and set

Ply or MDF depends on the finish you want; if you're painting it use MDF and dont use a water based paint if you're not priming/sealing it. If you find a nice hardwood ply sheet with an appealing grain and want that as your finish.. then use ply!

I've got some insulated hatch doors made out of kitchen worktop for the decorative element

 

[theflyingpig]

18mm mdf for face with insulation behind then thin sheet of ply or mdf , screw thru from rear which helps fix insulation ( glue as well).

18mm mdf for face with insulation behind then thin sheet of ply or mdf , screw thru from rear which helps fix insulation ( glue as well).

I think that would end up a bit thick... 18 + 25 + 9 = 52 mm....

 

[foxhole]

I think that would end up a bit thick... 18 + 25 + 9 = 52 mm....

3mm ply so 46mm.
Any thinner and too thin for hinges ,

 

[robinbanks]

It'll have an edging, so that can carry hinges

 

[msmsm]

You can get oversized fire doors that you can cut to size. Not insulated as such, but better than a normal door.

 

[theflyingpig]

Thanks... It's only going to be about 650mm wide so don't think there would be anything I could cut down....

 

[msmsm]

Fire doors are solid so can be trimmed to any size

 

[theflyingpig]

Fire doors are solid so can be trimmed to any size

Completely solid?

 

[freddiemercurystwin]

Yes solid but the edges need to be re-lipped where cut. Talking of which does it need to be a fire door? If it does then you might need to start off with a fire door blank, rather than a standard fire door, depending on what might need to be trimmed off.

 

[msmsm]

Yes. The edges need to be relipped if external or if you don't want to spend hours filling and sanding. I have used these in the past https://sheetmaterialswholesale.co.uk/plywood-door-blank-fire-door-44-x-915-x-2134mm-fd30/

 

[msmsm]

You can also get the fire door blanks MDF faced for painting, but they seem to be much more expensive.

 

[robinbanks]

If the aim is to make an insulated door, it would be better to use a cheapo door that has a cardboard honeycomb core rather than a solid wood door. Trapped air is instrinically insulating

Thinking something like https://www.wickes.co.uk/Wickes-Lisburn-Plywood-Flushed-1-Panel-Intenal-Door---1981-x-610mm/p/121594 that you can add onto at the sides, or if your "about 650mm" can be "666 mm" then the larger (same price) 686mm varaint can be trimmed to that size

 

[theflyingpig]

If the aim is to make an insulated door, it would be better to use a cheapo door that has a cardboard honeycomb core rather than a solid wood door. Trapped air is instrinically insulating

Thinking something like https://www.wickes.co.uk/Wickes-Lisburn-Plywood-Flushed-1-Panel-Intenal-Door---1981-x-610mm/p/121594 that you can add onto at the sides, or if your "about 650mm" can be "666 mm" then the larger (same price) 686mm varaint can be trimmed to that size

This is a good idea! Thanks