Contractor Talk - Professional Construction and Remodeling Forum banner

Slope a deck or a level deck?

164K views 30 replies 22 participants last post by  avenge 
#1 ·
I was always taught only slope a deck if it is going to have an impervious surface applied to it. Otherwise, all decks (with planks) shall be level.

I am replacing water damaged and rotten rimboard on a home and the home owner has a deck attached at the back with about 2" over 12' slope (away from the house). I asked him what was up and he said he built the deck and the book he used said all decks should have some slope. I told him my understanding of decks - but it sometimes is hard to argue with a book.

I say this is bad intel from this book. Am I loco or should I stand my ground and keep on building level decks? What say the deck masters?
 
#6 ·
The only decks I've seen that were built with a slope were ones on apartments that had lightweight concrete poured on second story decks. I did tear down a res. deck once that was also built on a slope, it was concrete with indoor/outdoor carpet glued to it. The framer notched his joist where they set on a beam to create the fall, not realizing his beam was all ready too low. It had about a 2" fall on a narrow 5' balcony deck, it would give most folks an uncomfortable feeling up on the 3rd story level.

A slope is for concrete only, not a deck with typical wood/composite decking. Properly flashed a level deck will not leak.
 
#14 · (Edited)
Even if attached to the house, if it is flashed well, what are you worried about.

I'm not as experienced as most guys, but I'll chime in anyway.

I don't slope unless it's waterproof.

In general "How-to" books are full of (censored).
However, just like anything you read you should always consider who wrote the book and what sources they used when processing the information it contains.
 
#15 ·
Even if attached to the house, if it is flashed well, what are you worried about.

I'm not as experienced as most guys, but I'll chime in anyway.

I don't slope unless it's waterproof.

In general "How-to" books are full of (censored).
However, just like anything you read you should always consider who wrote the book and what sources they used when processing the information it contains.
Just my .02 - Water seeks its own level & looks for the smallest opening - why chance it coming back towards the ledger.

As an FYI, as I stated above a slight slope - not 2" in 12' - that's just ridiculous
 
#18 ·
I built homes along the coast for twenty+ years and realized after a few years that shrinkage of the framing lumber would actually cause a level deck to pitch backwards over time. Anyone who has seen vinyl siding unlock at the floor line understands the concept. We decided at that point that all decks would get at least 1/2" of pitch per 8" of deck. We were framing with GRN lumber through the 80s and most of the 90s, before a fungus problem prompted a switch to S-dry lumber.
Perrsonally, I believe that everything possible should be done to get water away from the wall assembly.:thumbsup:
 
  • Like
Reactions: Winchester
#20 ·
Wow interesting how something like this has good points on either side. I think when it comes to carpentry we were all taught plumb and level as the gospel truth in most everything we build so it just seems un natural to make something out of level on purpose.

I was told sloping the deck as the above examples said like a ½” in a 12’ run was to prevent ponding and help with run off. If you do it to PT knowing every few years you’re re water proofing it I guess it would come natural when using composite.

Maybe the concept or misconception (depending how you view it) started with concrete and the t & g of old where it was needed and it just carried over to spaced decking and most just never question the rationale.

I’ve done nowhere NEAR the amount of decks Ya’ll have done so my method or reasoning might be wrong.:notworthy
 
#21 ·
I also have read about building fall into the deck frame,I dont agree with it, but I have seen it in print. Even when I put on T&G Ipe I dont do it no need with my seceret method.

If the deck has a roof under it of course the fall is defentley built in but other wize I cant see the value in it on a project done corectley. J.
 
#23 ·
I pitch them 1/4" per 10'. Its not perceivable visually to most people but gives me piece of mind. I was always taught water is the worst enemy of a house and to protect against it anyway you can. I've never had a problem attaching stairs or with railings looking out when doing this.
 
#24 ·
You never know what may be put on the deck surface or if it may have drainage under it. Nothing wrong with a small slope. Also it may heave up if it is a ledger installation and the posts are not set properly. Not as big a problem with free standing decks.
 
#25 ·
If anything I frame my decks with a very slight slope back towards the house. I'm talking about just leaving the line when you cut the post, on your typical deck with joists attached to the ledger at the house, and cantilevered over a girder sitting on 6x6 posts.
I also put a slight crown in the girder.
My feeling has always been that once you add all the weight of the decking, somethings going to settle at least a little. Especially when using decking like 5/4 IPE. Man, is that stuff heavy.
Even the pressure treated lumber weighs a lot, and could cause the footings to settle.
Whether it's the footings settling into the ground, post base settling onto the footing, or girder settling onto the post, somethings got to settle a little bit.
Again, I'm talking about just keeping things up maybe 1/16 over a 14' span. Hardly a slope at all.
The stairs are an issue, because I install my stringers before installing decking. So I want things pretty level at that point,
but the last thing I want is something to sag.
I do put a lot of care into flashing the ledger to the house.
 
#26 ·
Real quick...level!

One thing I noticed with all our replies is that not one of you mentioned getting a customer "call back" with regards to flooding or accellerated rotting. We all must be doing it right regardless of method.

Everytime I see one of those "how-to" books, I want to burn them. I am going to write a a "how-to" book...chapter 1..."Don't buy how-to books".

:thumbsup:
 
#27 ·
A lot of interesting thoughts on this subject. I have never built a level deck that was attached the a house.
It might come from my background in the concrete trades. just the thought of doing one level makes me feel ill.
I also know that their is more than one way to do everything. Just cause someone does something a little bit different than you doesn't make it wrong it's all in what the HO is happy with and will pay you for
 
#28 ·
Just cause someone does something a little bit different than you doesn't make it wrong it's all in what the HO is happy with and will pay you for
Well, yeah unless they're happy because they have no idea their house is rotting away from the inside-out. I would call that wrong :whistling
 
#29 ·
A deck with treated deckboards, level or sloped? If you build a 14'd deck and slope it 1", each deckboard (30 in total over 14') will be sloped approx .03". Then the gap between each board, the water is going to go there no matter what. If the boards are cupped/bowed, no difference on method. Spray some water on your sloped vs. level deck and see what happens...now results may vary depending on if you sloped it like a ski hill. It pools no matter what. That one board closest to your house is sloped .03" away (approx). Do you think the rain always falls striaght down and no water has ever gotten under your siding?

To install Duradeck, manufacturers specification for slope is 1/4" to a foot. I have talked to them a few times on this just to be certain. The first 3 decks I did...according to their specifications...I had to go back to reduce the slope or raise the end of the deck for the HO. They felt like they were falling or walking downhill. Spec'd this way why? To avoid replacement costs when vinyl does deteriorate...maybe, I don't know.

Low maintenance level or sloped? Probably sloped because they are expensive and you want to make sure you adhere to manufacturers installation specs, which is sloped.

When it rains, it rains from alot of different angles, sprays, splashing etc... Water goes everywhere and finds the path of least resistance for drainage. Lots of different opinions/arguements. If you want a leak proof deck, maybe think about an addition or covered deck.
 
Top