# Replacing Roof Boards



## joedadog (Mar 10, 2006)

When my roofing contractors does my roof he said he will be replacing any bad boards with particle board. Should he be using plywood or CDX plywood? Which is best? I have been on the roof and it is very very soft in many spots. I almost want to replace all the boards. The house was built in 1968 and I have trusses with 22" between each. I don't know if the current board are 3/8",1/2" 0r 5/8. Can anyone give me good advice? Thanks


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## lxdollarsxl (Apr 16, 2006)

For what its worth if it were mine, i would have it all resheated with 5/8 OSB, if im gonna have to repair parts of it and everything else is going to be torn off and replaced i would do it all. Also possibly add some more strenghtening to trusses


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## AaronB (Jan 29, 2005)

I do not ever use OSB. I dont like it. IT absorbs water like a sponge and then rots through in short order, from what I seen while doing repair work.

Sometimes you will feel soft and spongy simply because you have 3/8" plywood on 24" centers. I have torn these off on occasion and resheethed the whole roof pretty cost effectively, because we planned to do the whole thing this way.


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## joedadog (Mar 10, 2006)

Thanks. I did find that the boards are de-laminating and cracked when I was in the attic yesterday. If I have the whole thing re-sheathed, what type of board do you recommend. 5/8 Plywood or 5/8 CDX which is about $35 a sheet.


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## AaronB (Jan 29, 2005)

Where are you located? cdx is plywood. grade cgrade exterior sheething.


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## MJW (Feb 7, 2006)

Are you taking out the wood and replacing or are you sheathing over old boards? If going over, 7/16" is plenty good, even 15/32" if it's cheaper. I wouldn't waste money on plywood. It is strong at first, but it bends. bows, delaminates, unless it is 16" OC rafters or H clips are used. 5/8 over 3/4" boards is a waste. Put 7/16" OSB on, use drip edge, I&W, Tarpaper, and shingle it. 7/16 OSB is less than $9 a sheat.


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## MJW (Feb 7, 2006)

CDX OSB is the red stuff, sometimes cheaper.


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## Mike Swearingen (Mar 15, 2005)

CDX is C grade pine plywood on one side, D grade on the other and exterior grade glue is used in manufacture. Plywood has 4x8' solid sheets alternated with strips of sheeting with the grain running crossways from the solid sheets.
OSB is Oriented Strand Board made from compressed hardwood with exterior grade glue, and supposedly is cheaper and stronger than plywood. It is o.k. to use for roofing, but as mentioned, if it absorbs water, it's like a sponge. 
Around here, many of the roofers use OSB in the roof sheathing field and plywood on the edges. The fact of the matter is, both need to be kept dry or they will warp, rot, etc. 
If you're on 24" centers, I would definately go with 5/8".
Good luck!
Mike


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## MJW (Feb 7, 2006)

I agree to use at least 1/2" or 5/8" on rafters 24"OC and H clips.
This old of a house probably has 1x6 boards and hand framed. 7/16" sheathing goes on over this to make a clean surface to start with.


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## joedadog (Mar 10, 2006)

It is okay to go over the top of the old boards. I thought the best way would be to remove them and start over. But if no harm done, and the weight is ok them maybe it will be cheaper to 7/16" OSB over the top and go from there.


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## MJW (Feb 7, 2006)

joedadog said:


> It is okay to go over the top of the old boards. I thought the best way would be to remove them and start over. But if no harm done, and the weight is ok them maybe it will be cheaper to 7/16" OSB over the top and go from there.


The only way I've ever done it and the only way to do it IMO. I've never heard of anyone tearing off all the old boards.


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## joedadog (Mar 10, 2006)

MJW said:


> The only way I've ever done it and the only way to do it IMO. I've never heard of anyone tearing off all the old boards.


Sorry I am a Newbie, What does IMO mean?


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## MJW (Feb 7, 2006)

In My Opinion, sorry.


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