Pannel for back relief

[Astrolabe]

Hello,
Calling this a DIY project is rather grandiose but I thought some of you might be able to help me with my problem:
My partner suffers from back pain whenever forced to sit, stand, or lie down on an off-level surface. This includes most mattresses, where the surface is either distorted slightly by the springs or sags slightly in the middle in the case of mattresses without springs.
My solution, then, is simply to place a board under the bedsheet on her half of the bed. My question is what material to use, the considerations being of course cost but more importantly whether or not the board will actually stay flat or will sag in the middle with her sleeping on it (she currently weighs ~7 1/2 stone)?
Thankyou for your time.

 

[JohnD]

next time she visits the doctor about her bad back, get her to ask for a referral to a physio.

or if you can afford it, send her to an osteopath. They are really good at sorting backaches.

 

[Astrolabe]

next time she visits the doctor about her bad back, get her to ask for a referral to a physio.

or if you can afford it, send her to an osteopath. They are really good at sorting backaches.

She has been seeing a specialist in her native country for years, but we currently cannot afford to visit one in the UK.
Lying on a flat surface helps reduce the pain, but the flat we are staying in has a wonky floor. Perhaps if anyone's worried I should say I am not requesting health advice on a DIY forum and am not looking to hold people accountable for my partner's back pain.

 

[foxhole]

A simple piece of hardboard will give a flat stable surface on top of a matress.BUT having had a couple of ops for slipped disc's over the years I know there is nothing worse for back pain than lying on a flat hard surface as it provides no support to the curve of a spine therefor making the condition worse.Osteopath is £30-40 a session, you cannot afford not to have treatment.[In my opinion and experience far better than physio]

 

[joinerjohn]

A sheet of 25mm ply will provide an adequate surface for your partner to sleep on. With her weight only being 7 1/2 stone, it should provide ample support. It would be better if you considered two single beds (hers without a mattress) rather than a double bed though, as your weight will cause the mattress to sag on your side of the bed and she will roll off the ply towards you.