Milling Cypress for a Deck

Advice on how to process Cypress timber for use on an outdoor deck. July 30, 2009

A customer has asked me to build an outdoor deck with small stair with handrails. A local sawyer has a large quantity of clear cypress cants that have been air drying for a year or so. I am thinking of re-sawing them to 8/4 and using untreated for deck, treads and railing. This will see light residential use. How well will cypress weather? Is there any advantage to planing it rather than leaving rough?

Forum Responses
(Architectural Woodworking Forum)
From contributor N:
Well cypress is a pretty nice material and I have seen it hold up near a 100 years as a siding, I have not seen it in any deck older than 15-20 years or so, possibly itís not the best decking material. I would be cautious to use the wood in the rough and not planed. For one planing the lumber does slightly close the grain, a rough board absorbs much more water than a planed board. Two, I would hesitate to walk barefoot on a rough deck. And in the rough is going to weather faster and more than likely crack and splinter faster. For a railing I think it would be totally acceptable.

From the original questioner:
Thank you for your comments. Good points about planing to reduce water absorption potential. I should add that this cypress appears to be old growth - very clear and mostly 20 or more growth rings per inch of growth. The cants are boxed around the heart and are virtually all heartwood. (I am aware that second growth does not have the same decay resistance as old growth.)

For once, I have plenty of time for this job so I'm thinking of getting the material and re-sawing to rough dimension and letting it air dry for 6-10 months in an environment that approximates its final location. I will plane to final dimension as I build the assembly. The price is excellent ($700/1000 bf) so I can saw and plane for extra large dimensions, say 12/4 on stair treads and solid 16/4 on railing posts, etc.

From contributor C:
Cypress tends to produce false growth rings so aging it by growth rings is not accurate.