Laying hardwood floor over suspended floor joists; would any underlayment help?

[Neverfinished]

Hi, I'm about to begin lifting the original 'pine' planks flooring in my victorian terrace home. Then to lay American Ash (19Depth x 138mmWidth) planks, & I could just lay them again straight on the joists as originally. Being on the ground floor, there's the typical 3ft 6in ish 'crawl space' beneath, which has a well designed 'air-draught' thru; And at base just the original reasonably dry soil within brick foundations. See photo attached.

I've added 80mm of Celotex between the joists several years ago.

Original planks survived fairly well in the environment just described though had cupped, doubtless a long time ago, & had been 'face nailed'; I'm thinking I'd secret nailing this time thru groove in T & G might minimise cuping this time?

Would my new floor also benefit from 'shielding' from the elements, especially water vapour, down in that under-space? Perhaps I lay a 6mm plywood base ? &/or lay a Tyveck type breather membrane, on the joists ?

I've been a decorating, some carpentry, tradesman for years.

I'd much appreciate anybody's ideas / suggestions before I start. Thanks in anticipation !

 

[saveasteading]

I would lay a polythene sheet over the ground (solum) and simply turned up the walls a little.

That will keep most of the damp out of harm's way.

Use a sturdy matetial as youll be treading on it.

[Temp]

If you can afford it I would go for Engineered wood. The best are 14mm plywood with 7mm finish layer so 21mm overall.  The top layer is thick enough that it can be resanded the same number of times as solid wood (eg until the T &G fails). 

 

Can even get it ready finished with hardware oil. Shop around as its colour and quality varies.

 

Can go for wider boards with less risk of cupping.

Edited December 6, 2023 by Temp