Making & treating a garage side door

[Sprogginz]

I'm on a budget.

I've seen external doors for sale that have the correct width but not height.
At approximately just 188cm tall you can't buy a ready-made door that size and I can't find any that can be trimmed down to that size except this one which is about £135 with delivery. It's not that expensive but a bit scared if I screw it up!

I'm thinking of making a basic ledge & brace door using these and these which I can pick up myself. If this sounds like a plan (and possibly regardless of what type of wooden door I buy or make) what treatment or products should I use to weatherproof it as much as possible?

Here's a photo of the current door which is literally falling apart.

I'm hoping the door frames are salvageable or will last for a bit longer. I already have this (see photo) but I'm assuming it won't do since it's for internal use?


Do you think it's much better to get the one for £135 or know of anything better yet cheaper?

Thanks

 

[foxhole]

Sheet of ply clad with pallets timber makes a cheap external door.
Or nice solid door from scaffold board seconds.

IMG_1320

• foxhole
• 30 Jun 2016

Ledger and braced door from scaffold boards

 

[Harry Bloomfield]

Timber frame on the inside then an outdoor ply for the outer face.

 

[Sprogginz]

Thanks for your replies, I'm trying to find exterior plywood though.
Would this do?

 

[JohnD]

on an external door, ply is very prone to falling apart if damp gets in though any edge.

I used the ply you show for flooring. I left the offcuts outdoors, and the unused material under a tarp.

after a week of rain the offcut pieces were falling apart and the sheeted material warped and bulging.

 

[Sprogginz]

Thanks for letting me know.
I'm a bit stumped now with what I should use after having a look at what Wickes, Travis Perkins and Jewsons have got.
Should I stick to some cladding? It seems hardwood is the best for an external door but can't find any for the size and budget.