ipe decking over a roof and pool deck - concerned about cupping

gman323April 15, 2009

1) I am about to build a deck over a flat roof (slight pitch of 1/8"/1') that has reasonably good drainage. As with any flat roof there are some small areas of pooling. I was planning on using Ipe and am concerned about it cupping. The deck will be 2"-8" above the PVC membrane. I am in Los Angeles and there is usually very low humidity. The house is on the top of a ridge line and there is usually a moderate updraft; however, sometimes the air is still.

2) Another portion of the project is a pool deck. The deck is designed to be 6" above grade and the grade is currently dirt/fill. It is a "WET" area that will often get water from entrances/exits of the pool. What should I do to the subdeck area to prevent cupping so that I don't have to lift the deck 12" above the ground?

would using 5/4 x X make a difference and if so is it worth the 25% additional $?

does the spacing of the boards make much of a difference and what would be recomended? (it is going over a white PVC roof membrane so the tighter the treads the more attractive).

How valid are these concerns?

Is there a way to minimize risk?

I looked at some of the engineered products and they have similar requirements for ventilation. The engineered products are more expensive then the Ipe and I would prefer to use the Ipe but don't want to regret the decision.

The roof deck area is ~2000' and the pool deck is ~700' so the investment in lumber and installation is considerable.

I have used Ipe in Miami for docks and never had any issues. I really like the material and would like to use if practical so whatever suggestions you may have would be appreciated.

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john_hyatt

Your roof top deck has plenty of clearance,most of mine have the width of the stringers 1 1/2''. I would sugest using counstruction adhesive as well as SS screws be very sure the screws do not go thru the stringers be very sure as well during install you dont damage the roof...like hiting it with the edge of a board,droping a drill bit first on it,steping on a screw things like that. Your right if your going to use anything on it use the S American lumber not manmade material.

With your pool deck provide cross ventalation. This can be done with screen vents in the framing if this is not completly possible install floor vents in the decking combined with the frame vents. Cross ventalation is a vastley over looked but much needed addtion to any decking project. The gap between the decking boards will have no effect one way or the other venting your project unless there is air moving under it. If possble a drain system under the pool deck might help if done corectley but do not put a ground cover like plastic sheet/tar paper under it

1'' ipe will react the same way 3/4'' ipe will under the same conditions. The life span of both is also the same.

J.

    Bookmark   April 16, 2009 at 12:49AM
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gman323

Thanks John. I went with your advise and ordered the 3/4". What you said about the cupping makes perfect sense and the savings were considerable.

regards,
G

    Bookmark   April 29, 2009 at 1:06PM
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