[doughpat]

Hi all -

I am going to be building a deck above a garage ceiling. (well, half of the deck is above a ceiling, half is cantilevered out over empty space, second story). The platform, which has about a 1/4": 12" slope, is exterior plywood with a TPO membrane. The finished surface will be composite decking.

The slope is subtle, but I do want to flatten it out with angled "sleepers", which the decking will be screwed into. The sleepers themselves will be "floating" (i.e. no fasteners going through the TPO anywhere).

First: I'd like to keep the sleepers as thin as possible to avoid building up a tall platform. I believe the minimum thickness is whatever depth I want the decking screws to penetrate. I am thinking 1/2" at the absolute minimum (though I'd have to make sure I can get deck screws in that length -- 1/2" + the thickness of the decking, approx 3/4 -1").

Second: I assume that PT 2x material is the proper material for this? With lots of end-cut solution used along the ripped edge?

Third, and most important: These sleepers need to be really consistent, with minimual 'wobbling' in the cut. I have an OK table saw (Dewalt contractors saw) and a skillsaw. I'm not a master of either of them. I'm wondering what the best way to cut quite a few identical sleepers is. I'll need about 14 of them (assuming 16" OC) so that's quite a bit of ripping. I'm thinking that maybe some kind of jig/template should be made that can hold the board, and give a nice flat consistent edge for the skillsaw the ride against.

 

[Nealtw]

How high is the door threshold bottom above the deck now?

 

[doughpat]

How high is the door threshold bottom above the deck now?

Good question. There is actually a single step (approx. 5") down to where the composite decking will be.

I'm going to be using a thin (3/4") plastic tile (RaceDeck FreeFlow XPS) for a walkable surface on the step.

 

[Nealtw]

Good question. There is actually a single step (approx. 5") down to where the composite decking will be.

I'm going to be using a thin (3/4") plastic tile (RaceDeck FreeFlow XPS) for a walkable surface on the step.

So you will have the frame sitting in moisture and no to little air flow .
I would start with 2x6s and set them on hockey pucks to let the water flow below.



Cutting the taper is usually just snap a line and cut it with a circular saw. You can build a jig for that. the problem with any method is the bend that most lumber has so even a perfect cut may not be exactly what you want.

There are plastic shims in a variety of thicknesses that you can use for fine tuning.

 

[carpdad]

A regular saw guide (check the videos - snap to make) set along the line. Best if you can have a sacrificial base so the cutting lumber isn't overhanging and maybe wobble. Saw guide also extra lumber underneath so it's not overhanging.

 

[doughpat]

So you will have the frame sitting in moisture and no to little air flow .
I would start with 2x6s and set them on hockey pucks to let the water flow below.
.

I don't love the idea of the boards sitting in water....but the platform IS sloped (and I live in a dry place, 10" of precip per year and very low humidity). I suppose that some kind of thin, rigid plastic upon which the sleepers would sit would be a potential solution.

When you say hockey pucks, what exactly are you referring to?

 

[Nealtw]

Hockey puck like in the game on ice, they are hard rubber about 1"x3"

https://www.google.ca/search?q=hock...VCuZ4KHcAICIkQ_AUoAXoECA4QAw&biw=1093&bih=502

 

[firehawkmph]

Run your sleepers perpendicular to the slope. You won't have to cut any tapers. I used to do this on interior floors from converted porches. You can set up a stringline or use a laser to measure the height every 16" and just rip the sleepers to each width. Very simple.
Mike Hawkins

 

[doughpat]

Run your sleepers perpendicular to the slope. You won't have to cut any tapers. I used to do this on interior floors from converted porches. You can set up a stringline or use a laser to measure the height every 16" and just rip the sleepers to each width. Very simple.
Mike Hawkins

Trying to visualize this but I don't see it.

If the goal is for the top of the sleepers to be level, and the sleepers are running perpendicular to the slope (i.e. "downhill"), then I don't see how the sleepers don't need to be tapered.....

 

[doughpat]

Hockey puck like in the game on ice, they are hard rubber about 1"x3"

https://www.google.ca/search?q=hock...VCuZ4KHcAICIkQ_AUoAXoECA4QAw&biw=1093&bih=502

I like the concept of some kind of impervious 'riser' to get the wood up off the wet membrane, but I don't think hockey pucks are the answer....too tall, plus unless I used a ton of them they'd end up concentrating the pressure.

I think that thin strips of plastic that are ripped to a width of 1.5", then tacked to the botttom of the sleeper, would do a better job. I suppose I need to look at what plastics are available for such a use. Would probably need to be 1/8 - 1/4" thick, "rippable", and hopefully not terribly expensive. Could probably use acrylic but that stuff isn't cheap. Might be able to use scrap from a sign shop or something.

 

[Nealtw]

I like the concept of some kind of impervious 'riser' to get the wood up off the wet membrane, but I don't think hockey pucks are the answer....too tall, plus unless I used a ton of them they'd end up concentrating the pressure.

I think that thin strips of plastic that are ripped to a width of 1.5", then tacked to the botttom of the sleeper, would do a better job. I suppose I need to look at what plastics are available for such a use. Would probably need to be 1/8 - 1/4" thick, "rippable", and hopefully not terribly expensive. Could probably use acrylic but that stuff isn't cheap. Might be able to use scrap from a sign shop or something.

The idea is to get the wood up off the deck so it can stay dry, treated lumber today isn't your dad's treated lumber, we have to protect the top too. Yes there would be lots like every 3 ft on ever joist. But there are cheap.

 

[firehawkmph]

Trying to visualize this but I don't see it.

If the goal is for the top of the sleepers to be level, and the sleepers are running perpendicular to the slope (i.e. "downhill"), then I don't see how the sleepers don't need to be tapered.....

Sleepers wouldn't be running downhill, but side to side on the slope. No taper needed. Fire up your table saw and let 'er rip! (Pun intended.😁)
Mike Hawkins

 

[carpdad]

Firehawkmph means your sleepers will be laid horizontally in relation to the roof slope. Then easy to rip the sleepers according to the level line. His shims, but, were for inside leveling and he didn't have to worry about rain drainage. I assume yours is exposed to weather since you're saying they will be floating, so you need to cut to the taper. Why not practice and see how you do? Cut outside the line and take your time. 14 is very few to do. If not satisfied, cut another or try hand planing. The sleepers will need a layer of cushioning so the lumber does not wear out the roofing. Also search if tpo roofing is compatible with this kind of decking? Maybe it needs much more room for expansion or such?

 

[doughpat]

Alrighty, got 14 cut, think I'm going to cut another couple while I have my jig setup.

Basically just screwed two long 2 x 4's to a board, with a gap between them the width of another 2 x 4. I put the PT (future sleeper) into the gap and also added a strip of aluminum angle for a saw guide. Ran my circular saw against that. Worked real well.

As for cushioning...thanks for bringing that up. It was my impression that the TPO won't need it, but just for safe measure I think I'm going to put down a strip of butyl rubber under each sleeper. This will also add a (very small) elevation to each sleeper, helping it drain a bit.

 

[carpdad]

Check first if butyl is compatible with tpo. There was some talk in past about butyl incompatibility with other materials. is tpo pvc? Pvc has plasticizers or such. Other plastics or rubbers may have modifiers or such. One may melt the other. Sorry can't remember the specifics. I just learn the main facts after coming across them a few times and go back for fact checking. Check the general info or manufacturers' warnings about compatible materials.

 

[doughpat]

Check first if butyl is compatible with tpo. There was some talk in past about butyl incompatibility with other materials. is tpo pvc? Pvc has plasticizers or such. Other plastics or rubbers may have modifiers or such. One may melt the other. Sorry can't remember the specifics. I just learn the main facts after coming across them a few times and go back for fact checking. Check the general info or manufacturers' warnings about compatible materials.

@carpdad I think I owe you a beer. I am so glad you posted this potential incompatibility between the Fortiflash and the TPO. I did some more digging and was convinced enough to go pull it all off (not too bad, but sunnier areas had already started really bonding...was a bit of a PITA). Then I called a couple roofing supply places and they said definitely do not use it. They had flashing specifically made for TPO (Karnak Fast-Patch, I believe it was). Just got done laying THAT down, and feel way better knowing there is a bit of a wear-guard under each stringer.

So, that chapter has ended, and I thank everyone for their input! The deck will now be level, and the TPO tape had the effect of lifting the risers about 1/32" above the rest of the deck. Not a LOT of drainage, but better than nothing and, as mentioned, I live in a dry climate and about half of this deck is covered by an overhang. I also painted all the cut surfaces (which I faced up) of the ripped angled sleepers with wood preserver.

 

[carpdad]

Great! Now I know too.:smile:

 

[Koa]

Pedestals? Make your own panels?

https://bisonip.com/

 

[sixeightten]

Hope you didn't taper those down to just 1/2". Screws need more meat than that to hold, and the wood will be more likely to split also. We just did a sleeper deck recently, and tapered down to 1 1/4". We used the hidden clips, so screw length was shorter anyway.