My builder is trying to fit these to the back of our house – it faces WSW so gets a lot of sun (and wind and rain).
Will they be up to it, it’s an engineered softwood.
Any sensible alternatives?

Jeld-wen Farndale Patt 70 French Door sets

Why is it going to be any more susceptible to warping than any other engineered wood? The softwood is literally a thick veneer and the main structure will be ply, the same as any other.

Performance

As solid doors are made of whole intersecting pieces, there is an inherent strength that comes from the construction. They are, however, susceptible to environmental changes such as variations in humidity and temperature. Exposure to factors like these can cause a solid door to warp or bow, making it twist and gradually lose shape.

By having layers of timber running in different directions, an engineered core is able to evenly distribute any stress applied to it. This makes an engineered door far more stable than its solid counterpart. This modern construction technique also provides better thermal insulation than that offered by more traditional methods.

Pros and cons

Solid internal doors and external doors, particular hardwoods like oak, will always have a premium allure to them. There’s an undeniable attraction to products with a solid hardwood construction, but they might not always be the best choice for your project. It’s highly likely that an engineered set will out-perform your solid option for less money, and, as building regulations call for better thermal insulation, your final decision could end up being a no brainer

https://www.aspire-doors.co.uk/blog/the-difference-between-solid-and-engineered-doors/

It depends how long you plan to stay in the house. Wood facing the weather and sun will definitely deteriorate especially if you don’t maintain it. We replaced our rotting, sagging wood back door that faces SW with an aluminium/wood/aluminium laminate door and it is quite astonishingly good, warm, stable, solid, even the paint is still looking good 12 years after application (it was Little Greene so you’d expect that).

I think I’m most worried about the veneer – hopefully if I keep on top of the maintenance it will be OK.

Softwood doesn’t necessarily mean it’s any softer. Doesn’t say what they use, but hopefully it’s something naturally rot resistant like larch or cedar. That’s more important.
If larch it will be a lot softer than, say, oak, which means it’ll take a dent easier, but not necessarily rot or decay quicker. Softwoods andbhardwoods will all silver off outdoors unless a finish is applied.

I had engineered softwood windows and doors installed into my house when I built it in 2005. They are very heavy, solid construction and the paint is still perfect. I’d definitely recommend.

I’d have no worry fitting proper engineered softwood doors. Fitted properly and properly painted on ALL edges and sides they will be fine.

There can be a misconception with soft and hardwoods, obviosly everyone knows that oak is a hardwood and very durable. But bear in mind you can get very low grade hardwoods too, Bulsa wood is a hardwood as an example… And you wouldn’t make a set of doors out of them!

I’m a carpenter with 20 years experience handling wood…

If you are to paint them I would advise using Sikkens paint or Dulux trade wethershield 3 layer system.
If staining then I’d use either Osmo UV oil or Sikkens stains.
Go along to an official Dulux decorating center and ask for there advice on coatings.

https://www.jeld-wen.co.uk/products/patio-doors/products/patio-doors/?productId=9419

40 year guarantee it appears

Hard vs soft wood is not really the whole/right question, as mentioned above. Some species will rot a lot more quickly then others. I’d be concerned about something just referred to as “softwood” and want to know more, especially having replaced a number of windows described as such recently, at only about 10 years old.

Also, whether water will sit or not depends on the design detail. An equally important thing to consider.

They are factory painted with micro porous paint which has lasted perfectly for 14 years so far.

Teknos paint?

If you’re looking to reduce maintenance then might be worth having a look at Accoya – uses some clever chemistry to provide significantly better durability and rot resistance.

Teknos? Probably, they are spray painted in the factory with about five coats. As I said earlier, they are still in perfect condition. Laminated softwood is stronger than hardwood apparently and very heavy. I’ve been very pleased with them.

+1 on Sikkens – amazed how well it’s done for 5 years here on wooden, South facing windows that had been ignored for a decade before.

Jotun I’m also really impressed by.

IMO, the paint and weather detailing is as important as the door construction.