Tongue and groove over a waterproof plywood underlayment

13 years ago

I am installing a tongue and groove deck on a craftsman style front porch. The front porch is pitched away from the house and has a 1/2" plywood underlayment. I have flashed the entire inside area and created drain holes on the face of the porch. I plan to waterproof the wood with tuff rubber. Once I am done, I am not sure how to secure the planks. I'm afraid if I nail it, the nails will pierce the waterproof layer, rendering it ineffective. I was thinking of using strips of self-adhesive flashing where I will be nailing. Also, I'll need a solution to let the water flow underneath the flooring surface. What should I do?

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thundata
Original Author

13 years ago

Answers to your question. I'm on a raised foudation. Pads and footings. The front porch is on its own footing which runs the perimeter. This is a new construction project. As of now, very little water gets on it, but I'd like to be able to spray it with a hose if necessary. I just don't want the wood to rot. The drain holes are pretty standard for craftsman front porches. Small 4" x 2" openings at the very front wall of the porch that water can empty to. I have included a link to the project. Thanks for your help

Here is a link that might be useful: Image of porch

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Comments (12)

john_hyatt
13 years ago
Do Not Do Any Of That.

John Hyatt www.deckmastersllc.com
aidan_m
13 years ago
How much water gets on the porch the way it was?

Where did that water go?

What do you mean you created drain holes on the face of the porch?

Does the foundation of the house also support the front porch?

If so, this is bad. Foundation space is the last place you want water. If the porch is open underneath, supported by its own piers, totally separate from the house foundation, it is OK for some water to get underneath. Make sure the ground drains away from the foundation. The front and sides of the porch must have adequate openings to allow ventilation. You do not want water to puddle on the ground and remain wet in either case.

This project seems ill-advised. You may have already opened up a can of worms here.
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john_hyatt
13 years ago
Aidan,before I even start, how long do you give this project? say with no decking placed at all.
J.
sierraeast
13 years ago
If you have room for the extra height, you would be better off running sleepers over the membrane and laying your deck boards over them. The sleepers could be 1x2's @ 12" 0n center as they dont need to be structural and they should be pressure treated or redwood. The sleepers can be layed out similar to joisting and fastened through the membrane with stainless steel screws. Dependent on your membrane type, the fasteners should be sealed by the membrane when proyruding through. By applying your decking directly over the membrane, moisture/condensation will be trapped between the membrane and decking causing pre-mature rot.
john_hyatt
13 years ago
John agrees with the Sierra.

I would not fasten the stringers thru the membrane at all. If anything I would use outdoor adhesive,tightbond makes a good one, and glue them down.

Defentley do not fasten the decking down thru the membrane. JonMon
sierraeast
13 years ago
Right on! Gluing makes more sense. Done right it will also keep moisture/condensation from getting under the stringers.
thundata
Original Author
13 years ago
So should I waterproof the plywood first and glue the stringers to the membrane, or glue the stringers to the plywood and then waterproof everything all together? What about nailing the stringers through the membrane and caulking the edges where the stringers meet the membrane? Also, how should I fasten the boards to the stringers - glue or 1/2 brads?
john_hyatt
13 years ago
This "tuff rubber " product is unknown to me as a membrane they do make boots I have used.

Your pictures show something already on the plywood. If this were my job to bid >>> Torchdown modified or cpo roof over the plywood, ground contact pt stringers laying in the direction of the flow, screw the decking to the stringers not past them into the roof. Do not fasten the T&G decking with a nailer. Using Construstion adhesive on the joists and stainles steel screws run the screw thru the G.

Do not place this decking the same way you would fasten a floor inside your house. Reread. Again. One More Time.

Request your Roofer Contractor flash and roof over any drain holes you cut in that plywood. The drain system you are thinking about is flawed.

Data,you might just have come to the right place your total plan will come back to bite you really hard in a short time.

John Hyatt www.deckmastersllc.com
Robert Rebimbas
5 years ago
What was the outcome of the tongue in groove over plywood porch?
HU-276578444
last year
I dont understand underlay beneath tongue and groove for external (somewhat) application. moisture between T&G will trap. If this is for support than framing is wrong.
millworkman
last year
HU-276578444 since it was 11 years ago, I am sure it has rotted by now and been redone. I would not concern yourself with the framing.