# How to redirect water from deck above?



## Jerry McColgan (Feb 8, 2008)

I have a somewhat unusual situation in that my outside layout runs on a two level deck that is actually below a deck above. 

The problem with this is that rainwater flows from the deck above onto the deck below and although I have put some corrugated fiberglass sheets above part of the lower deck, since the "ceiling" is flat the water does not flow well anywhere. 










This old photo shows the screened section and in it I have a bit of a slope but no guttering or anything to drain the water away. 










I am not much of a carpenter so I don't know much about how to properly slope and drain water falling from above. 

It has been about 8 years since I built the deck for the original outside layout and the fiberglass is becoming brittle and probably should be replaced so I am starting to think about replacing it with something and I would like to have whatever I do drain the water away. 

Any ideas on how this should/could be done with a minimum of labor? I am a lot less mobile than I was when I built the layout. 

Thanks, 

Jerry


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## Guest (Jun 10, 2008)

making an impermeable floor on the upper deck?


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## Torby (Jan 2, 2008)

You're close with your coorugated fiberglass. 

Use a block of wood over one end of the "first" sheet so it slopes. 

The "second" sheet goes under the first so water runs onto it from the first. Put 2 blocks of wood over the second, so it continues to slope. 

Continue putting blocks and sheets till the water runs off past your lower deck.


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## Torby (Jan 2, 2008)

Of course, see your post about AAADD before you try this.


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## Mike Reilley (Jan 2, 2008)

The way I'd approach it is: 

a. Install a gutter down the length of the supporting beam on the inside with a downspout at the end. Use solid gutter material...metal..not vinyl...because it will be supporting a fiberglass panel. Attach it well. 









b. The gutter will have to slop down as it runs towards the end of the deck. Install a downspout at the deck end and attach it to the last post. 

c. Install 2x4 pieces between each rafter against the house to support one end of a fiberglass panel. 

d. Cut fiberglass panels to run from the house to the gutter. They should be cut to the width of the deck rafter/joist space so that they fit up into the void between the rafter/joist snuggly. 

e. Install the panels so that one end rests on the gutter and one end rests on the 2x3 piece installed in step (c). Predrill a hole on an angle up through the 2x4 through the fiberglass...like in toe nailing. Then run a coated deck screw through it and the fiberglass panel to hold it in place. 

f. If the fiberglass panel sags at all...put some 1x2 blocking along the edge of it and screw it into the rafter/joist. 

Here's an illustration to help


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## Jerry McColgan (Feb 8, 2008)

The upper deck is made of 2" x 4"s and spaced to allow water to flow through to help keep the wood from rotting. Eventually I need to replace the floor with proper decking but will still need to space the decking to keep the upper deck water free. 

I've been planning on replacing the upper decking for at least 10 years now. 

Thank you for the suggestion, 

Jerry 



Posted By kormsen on 06/10/2008 9:48 AM
making an impermeable floor on the upper deck?


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## Jerry McColgan (Feb 8, 2008)

Hi Mike, 

I like your idea but my main concern with it is that I do not have a way to accurately cut the material between the rafters. I bought a table saw years ago but gave it to my son recently somewhat rusted and unused. Table and Chain Saws scare me and I try to avoid them as much as possible. 

I would like to build something below the rafters that would call for less precision in building. 

The deck has about 12 foot ceiling so I do have some height to play with. 

Perhaps something similar but about a foot lower? 

A minor detail is that it would need to drain toward the garage doors otherwise the water could collect under the lower deck which is not well drained. 

Thanks, 

Jerry 

Posted By Mike Reilley on 06/10/2008 12:17 PM
The way I'd approach it is: 
a. Install a gutter down the length of the supporting beam on the inside with a downspout at the end. Use solid gutter material...metal..not vinyl...because it will be supporting a fiberglass panel. Attach it well.


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## Bob Starr (Jan 2, 2008)

OK, since I do stuff like this for a living let me offer my suggestion. Mike's method is a viable method and would only require you to put a ledger board under your deck supports and would not require you to cut to each joist of your upper deck. A bit of an exagerated slope in his drawing tho. 
Up here in our mountains, we have a lot of decks over rooms and the common way to do protect what is below is to cover the deck with plywood and cover with the many types of fiberglass sealing systems. When you put the plywood down, you shim it to slope to whatever direction you want to run your water. 
Here is a link to the brand that I commonly use: 
http://www.lifepaint.com/lifedeck/fmsystem/index.html


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## Jerry McColgan (Feb 8, 2008)

Hi Bob, 

This idea (plywood) is something that never occurred to me and I like it. 

One problem would be that I would be putting the plywood on top of 30 year old 2" x 4"s (fairly warped) and I would not know how to shim it and angle it in a way that it would support my 300+ lb weight. 

I presume that treated plywood would be necessary? How thick should the plywood be? 

How much of an angle should be used? 

Thanks, 

Jerry 

PS: I don't know what a ledger board is. 


Posted By Bob Starr on 06/10/2008 6:53 PM
OK, since I do stuff like this for a living let me offer my suggestion. Mike's method is a viable method and would only require you to put a ledger board under your deck supports and would not require you to cut to each joist of your upper deck. A bit of an exagerated slope in his drawing tho. 
Up here in our mountains, we have a lot of decks over rooms and the common way to do protect what is below is to cover the deck with plywood and cover with the many types of fiberglass sealing systems. When you put the plywood down, you shim it to slope to whatever direction you want to run your water. 
Here is a link to the brand that I commonly use: 
http://www.lifepaint.com/lifedeck/fmsystem/index.html


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## thekollector (Jan 2, 2008)

Lowe's offers a corrugated plastic under deck system with brackets designed to establish slope for drainage. I used it over the heat pump. (dogs use the deck above ;-)) 
But you would have to add a gutter. 

Jack


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## Bob Starr (Jan 2, 2008)

Posted By Jerry McColgan on 06/11/2008 6:30 AM
Hi Bob, 
This idea (plywood) is something that never occurred to me and I like it. 
One problem would be that I would be putting the plywood on top of 30 year old 2" x 4"s (fairly warped) and I would not know how to shim it and angle it in a way that it would support my 300+ lb weight. 
I presume that treated plywood would be necessary? How thick should the plywood be? 
How much of an angle should be used? 
Thanks, 
Jerry 
PS: I don't know what a ledger board is. 
Jerry, 
How far apart are your joists? 2 x 4 are a bit unusual for decks, they are usually 2 x 6. The ply, or rather what I use is OSB (the chip board, cheaper) should be at least 1/2", but it depends on your joist spacing. If you were to start with 3/34" furring strips (1.5 x 3/4") at your highest point of your slope and work your way down to deck level you would have enough slope. It would be important to fill any of the low warped spots with support so that they would not sag. Not necessary to use pressure treated as the covering will protect the wood, but painting the underside of the plywood makes things hold up better. A ledger board is the board that is against the wall of your house that supports the deck.


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## Jerry McColgan (Feb 8, 2008)

Hi Jack, 

I started with corrugated plastic (Fiberglas?) but I had no "system" and used too thin a material that has not held up and had no drainage (it was flat). 

The lower screen room has a working ceiling of corrugated plastic that is still working except that I need to figure out how to make a gutter for the lower end of it. 

I will probably end up with some sort of mixed solution of different ways for protecting the open lower deck and the screened room. 

Thanks, 

Jerry 



Posted By thekollector on 06/11/2008 7:14 AM
Lowe's offers a corrugated plastic under deck system with brackets designed to establish slope for drainage. I used it over the heat pump. (dogs use the deck above ;-)) 
But you would have to add a gutter. 
Jack


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## Jerry McColgan (Feb 8, 2008)

Hi Bob, 

The joists are 2" x 8"s and they are spaced 16" apart. 

Both the guy who built this house and the 2nd owner who built the deck were apparently stretching their finances when they built the place so while the overall quality is very good there were some shortcuts that were taken. 

The 2" x 4"s for the upper decking are apparently one of those shortcuts that were taken. 

I built the lower deck and while I am not a qualified builder or carpenter it is probably overbuilt if anything and I built it with conventional 2" x 6" treated decking. 

If you don't mind I may follow up later with you when I eventually get around to doing something. I like the idea of the plywood because I realize that I do have to rebuild the upper decking one way or another fairly soon. 

All of these comments have given me a lot to think about and I appreciate it. 

Regards, 

Jerry 


Posted By Bob Starr on 06/11/2008 8:13 AM

Jerry, 
How far apart are your joists? 2 x 4 are a bit unusual for decks, they are usually 2 x 6. 

The ply, or rather what I use is OSB (the chip board, cheaper) should be at least 1/2", but it depends on your joist spacing. If you were to start with 3/34" furring strips (1.5 x 3/4") at your highest point of your slope and work your way down to deck level you would have enough slope. 

It would be important to fill any of the low warped spots with support so that they would not sag. Not necessary to use pressure treated as the covering will protect the wood, but painting the underside of the plywood makes things hold up better. A ledger board is the board that is against the wall of your house that supports the deck.


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## Bob Starr (Jan 2, 2008)

Jerry, happy to help in any way that I can. Just give me a holler


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