Tearing off flat roof

[grrepa]

Hi,
Here's a question that I hope you can answer. My husband and I are tearing off our flat roof (California home built in the 20's) Now that it's exposed, there's no plywood, only planks about 6-7" wide. Between these planks there are spaces up to 1". This doesn't seem right. My husband wants to lay the new roof over this, without covering it with plywood or some type of insulation board. Would this be correct, or should be lay down plywood over these "planks"?
Thanks for any help you can give.

[Rich]

I personally would lay down plywood or some type of structural insulation (tapered maybe?). In honestly I don't believe it's absolutely necessary but there will be the possibility of puncturing the roofing between the planks if you ever walk on it.

[mjpliv]

More than likely any roofing product you appy will have minimum requirements for a base in order to keep your warrenty valid. I would hazzard a guess that the description for a suitable base will include the words "smooth, clean, even and continuous" and perhaps even "without voids".

[grumpydasmurf]

Fact is most flat roof manufacturers hate warrantying residential :)

If it were my house I'd lay plywood over the wood. You will need a nailing/fastening base for your roof system if you plan to mechanically fasten the system. What system are you installing?

[grrepa]

Thanks for all responses. They were of enormous help. We plan on installing a new 12 yer roof. torch down application. flintlastic brand white-granulated surface. nail down a layer glass base underlayment. new metal flashings around roof vents and pipes. seal and paint to match. remove old drains and replace thm with new drain scuppers. two inch can strip around parapet walls with tile copping on top parapet walls.
So should we place plywood down on the "spacer boards" before we install the new roof? This is the big issue we are facing. thanks in advance for any advice

[grumpydasmurf]

A home owner with a torch! Did you remember to mail in that insurance check? I highly recommend a self adhering (SA) system. SA has No open flames.

If you do insist on the torch I recommend two layers of felt base (underlayment).

I think for best quality you should lay down plywood, or at least some OSB over the existing boards. Make sure to elave a 1/8" gap between all boards for expansion/contraction.