What sort of birds have you got? If they are large, a metal frame might be better. I went for hard wood (Iroko) for my latest aviary. The mesh is stainless steel. It is attached to the house so I only have to open the French doors when the weather is warm.
The above seems more popular with my birds than the aviary we had in London which was aluminium and galvanised steel. It was also attached to the house. I was never happy having galvanised steel even though I washed it down with vinegar and water as suggested.