Repairing a sagging sofa

[Sue]

I have a very large (at least four seater), very old (bought when I moved in circa 1990 🙄) sofa which I am very fond of. It was extraordinarily expensive (from Heals)  at the time.

It has loose covers and large  feather filled cushions (on the seating part).

It is completely sagging at one end (the end I usually sit) and I think the springs have "gone".

Some time back I had a quote to repair it, and I can't remember what it was, but it was a lot, so I decided to put up with the sagging as it's not too bad if the cushion is plumped up. 

Every so often I look at other sofas, eg corner sofas,  but I can't quite bring myself to say goodbye to this one.

To get to the point. There are various DIY solutions online for sagging sofas eg putting a sheet of hardboard or something specifically made for this purpose beneath the cushions. 

However there seems to be mixed views on how successful this is in terms of comfort.

Has anybody tried this, or other remedies? Did it/they work?

I know I could just try it and see, but it seemed to be a good idea to ask first!

Edited Monday at 14:09 by Sue
Typo

[tropica]

I have a sofa of similar age, which used to sag, and I spent a stupid amount of time with the supposed 'DIY' solutions, which are all a waste of time and money. Then I woke up and realised that it can't be rocket science.

When you say that the springs have gone, do you know what sort of springs you have? If they are zig zag (sometimes called serpentine) springs then it's an incredibly cheap and easy thing to fix by anyone with a hammer, screwdrivers, possibly pliers, and new springs which can be bought from https://www.jamiltonupholstery.co.uk/product/sinuous-springs-with-fixing-nails/ Obviously you can also get them on that well known website that we're all trying to avoid. 

If they are box springs, then you may be able to replace a single spring, or you may have to change the whole unit, still DIYable but you may need a friend to help you. You may even find that a spring has simply come loose and it just needs clipping back into place.

Access to the springs may mean undoing the upholstery under the cushions, or it may be that you have to turn the sofa upside down. The feet usually just unscrew and then you can take the dust cover off the bottom to see what's what.

There are loads of YouTube videos to help but please DM me if you need any help.