Bathtub support - is a metal plate required?

[Bored Shopper]

Need advice please: FF bathroom is due to have a square(-ish) bathtub (1050x1250mm, 600mm deep). Total water capacity 428l. Users will be above 110kg.

Now the floor structure is  timber joists N. G2,47*250mm Grade C24@0.40mCTRS (taken from SE plans). We've made that double joists, bolted together. The new builder (we've had a change of builders this months, don't ask...) says it would probably need a metal plate support on top of joists to ensure the full bathtub does not cause joists movement. Architect says maybe not. 

 

Any opinion please?

[nod]

I used 

I joists  under our 60 KG tub 

I doubled a couple up under the tub

Mainly because I hadn’t used them before Boarded them with 22 mil Caba board and 15 mil Porcelain on top Then the tub

 

I spoke to the floor design company at the time and they said while I could double up there was no need