Exterior deck

[ajk1]

In the attached deck detail, it specifies no gaps between the p.t. boards. Is that accepted practice? I thought that there should be gaps to allow drainage and avoid wood rot (even p.t. wood will eventually rot).

 

[MikeHalloran]

The phrase 'no gaps' suggests that the designer has never actually built a deck.
Especially odd; the section is drawn with visible gaps.


Mike Halloran
Pembroke Pines, FL, USA

 

[jayrod12]

To be honest. All the pt wood I've seen is so moist that even if you install it tight you end up with sizeable gaps

 

[ajk1]

Doesn't the term "brown wood" mean that it is seasoned (as opposed to "green wood")?

 

[jayrod12]

Maybe. but depending on whose mouth it came from it might just mean the brown cedar-tone pressure treated lumber over the green pressure treated.

 

[Canuck67]

Without gaps, it is sure to rot prematurely, even with pressure treated, unless perhaps it is a very dry area. The green pressure treated wood, in my area, is becoming harder and harder to get, the brown coloured pressure treated wood is taking over. Perhaps a misguided attempt to make a dryish area underneath the deck for a walkout basement type scenario or similar.

 

[Brad805]

Where would one go to find the so called "dry" 5/4 material? Wholesalers dealing to cabinet makers supply hardwoods at "dry" moisture content, but I do not recall any that sell 5/4 deck boards. Nobody would want to pay for it as it would be 50 - 100% more if you added in the extra kiln time (or air drying time) nor does it make sense to spec such a wood where it is known to be in a wet service condition. Go to

http://www.advantagelumber.com/wood-decking.htm

In addition to the shrinkage that will occur, the other problem is 5/4 boards are never straight. You can bend them however you like, but one must be practical. If this designer wants no gaps, they need to consider a different finish that goes over sloped treated plywood.

 

[CANPRO]

I think jayrod answered your question. You install it tight so that when the wood dries out, you don't end up with overly large gaps. I was taught to install the decking as tight as possible for this very reason. Having built a few decks around my own home I've seen the gaps appear over time. Never had an issue with rot.

 

[SlideRuleEra]

Intentional gaps between deck boards are essential for good performance in a humid climate. In a dryer climate, I understand why gaps during installation may not be required

Man made 5/4 deck boards, such as the "Trex" brand provide better looks and durability than typical pressure treated decking. All members are straight, uniform quality (no knots), do not require maintenance (painting or staining). They are typically the same width as wood decking (nominal 6", actual 5 1/2") and they do require intentional gaps between boards. Initial cost is higher than pressure treated decking and they will uniformly change color due to weather in the first year, or so. If life cycle cost is considered, they are competitive with pressure treated decking.

Here is a link that lists several brands, Trex is the only one that I have first hand experience with:

http://www.deckspecialists.com/composite_deckmaterials.htm

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[manstrom]

I've never heard of "secure-a-deck". Looks fishy, is there a tested report for it?

I couldn't find anything in a quick search. Is that designed for vertical load? What is the capacity?

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[racookpe1978]

There are several under-deck finish systems (usually laid-under plastic strips) that rain-proof under a deck with gaps.

 

[ajk1]

Having 50 years experience, I would never install real wood decks without gaps between the boards. It will rot for sure. Guaranteed.

The rain water will accumulate on the deck (perhaps not a problem in an area of little rainfall like Arizona or the dessert). CANPRO, if you are installing them tight and it has not rotted, I have 2 questions: a)is it real wood and b) how old is it?

 

[CANPRO]

a) yes it is pressure treated SPF 3/4" decking. b) 5 and 10 years old.

I was taught to build decks this way by my father (30+ years as a carpenter). He built the deck on my family home this way 20+ years ago and the decking is not rotten. It gets some fresh stain every few years as it should. All the decks now have slight gaps in between the boards and drain freely.

 

[CANPRO]

ajk1, see link below...about half way down they have a little note on spacing the decking. They make a good point about the initial condition of the wood. If you're installing it dry, you should have a gap, if not it can be tight. I guess it depends on the local supply. I've always installed the decking tight and have been left with slight gaps in time....perhaps the decking I've dealt with has a higher moisture content than what you've dealt with.

http://www.hometime.com/Howto/projects/decks/deck_11.htm

 

[IceNine]

I agree with CANPRO, when using pressure treated wood, I install the boards tight and always end up with a space between boards 1/4" or more. If you space them, you'll end up with even bigger gaps.
I've never used kiln dried untreated wood, sounds like you'd want to space those boards.

 

[ajk1]

ok, if you end up with a drainage space.