|Home » Forums » WOODnetWORK » Message||Login|
You are not logged in. Consider these WOODWEB Member advantages:
Teak boat decking over concrete4/20
I have this project to install 2500 sq. ft. (275 sq. meters.) of 2” plank teak decking w/silicone expansion joints (boat deck) in a custom home here where I live and work in Thailand. I have done this work before on boats but never in a home and never over concrete. This will be installed in many different applications i.e. bathroom, bedrooms and exterior covered decks and next to a Jacuzzi I got to reject the gluing of teak directly to concrete for many reasons not least of all spring or the lack of (springiness) and drainage in case of breach in the deck. My idea is to slope the existing floor and anchor galvanized furring on built up (leveling) mortar beds 16” on center in the direction of my slope then sheeting all that in plastic as a moisture barrier. I would then lay a substrate of 5/8” to ¾” marine ply over that with many weep holes drilled in it for drainage. Every part of that process would be coated with an appropriate sealer and the down slope end (under the plywood) will have a 1” PVC pipe for drainage. I must qualify that this is in a high end luxury condo on a private beach so suffice it to say budget is not and issue, the customer wants to feel like he’s walking on the deck of a luxury yacht and he wants a guarantee that their will be no problems or go backs.
I assume this is an existing home, since you state you plan to "slope the existing floor".
So you are going to raise the floor level 3 inches plus the pitch/rate of rise??? How will you alter/work around the plumbing, cabinetry, interior/exterior doors, etc?
I would think you would need a slope of 1/2" in 12" to get complete drainage, so a 10 foot wide room would have the floor raised 8 inches. And sheet plastic over concrete (IMHO) is a bad idea, as the concrete will likely always be damp from sweat.
There is a "designer" involved but he/she can't tell you how to make this work...and you have a client who has already stated he wants a problem-free floor. I don't mean to be negative or discouraging to you, but this sounds to me like a nightmare waiting to happen...and I guarantee you will have a "breach", especially if you use silicone.
I hope it works out for you. Please check back and tell us about your progress.
I here what your saying but here in Thailand they make every structure from concrete. Steel reinforced concrete post and beam construction. The structure are all built on an understood engineering spec. of the 4 meter cube (girth of post beams rebar schedule etc.). In the resort town I live and work in they build condos up to 50 stories based on this concept they post and beam up 1 floor they brace tons of scaffolding just under the tops of those beams put plywood on top and pour the floor (6" thick) for the next story and then repeat. The walls are all 2 1/2" thick brick curtin walls basically stuccoed flat. So you end up with a concrete or masonry box. The beach front luxury 4th floor penthouse that I'm working on is a bare shell open to interpretation. The hallway entrance is my only grade restriction and the condo is already about 3" below that all the labor here is dirt cheap and skilled almost exclusively at working with... you guessed it "Concrete". Concrete it self is also very inexpensive. So! That being said it's a very unique set of circumstances compared to what we are used to in the states. I know that I could not expect you to know all that but I was hoping to get advice with out boring you with the details. I am angling to be superintending this job so I hope to have control over all these things.
I'm very for your input and help. end of my last message go cut off
You've already given this quite a bit of serious thought ...here are a few of my own ideas.
A "floating floor" installation might be your best approach. This leaves the bulk of the wood floor completely separated from the concrete.
Begin with wood furring strips (teak) fastened to the concrete. These strips must not be able to trap or dam-up any water (or air) beneath the floor. You may need to cut small cross-notches to provide drainage as well as air venting.
Marine plywood underlayment is next and is completely sealed. It is glued and screwed down to the strips.
The actual teak planking should be at least 3/4" thick (and not 3/8" or engineered flooring). The planks should also be "quartersawn" to avoid cupping. You might consider a typical tongue and groove plank but with a cut-groove that will leave a 3/16" gap between the planks after they are nailed up tight against each other. This gap (above and below the tongue) is filled with the black adhesive chalk (two-part Polysulfide). The planks can also be bedded down with this same stuff (or glue) and screwed or toe-nailed down through the tongue.
The fastenings (screws or nails) should be nonferrous like bronze or Monel, or maybe those specially coated "decking screws". Avoid the use of any galvanized angle irons or plated galvanized steel anywhere! (Galvanized steel just takes a little longer to rust).
Slope all exterior decking to provide for drainage and install marine (cockpit) style deck drains with plumbing or flush grating plates.
This kind of installation does not rely entirely on some "space-age" epoxy to hold things down. The glue as well as screws provide for positive and permanent adhesion. The thickness of the planks themselves also allows for fastening through the face with plugged holes, and a lifetime of sanding and refinishing as required.
An exterior teak deck like this should not be finished "bright". A varnished deck is a slippery surface and varnish itself is generally to soft for foot traffic. You might consider a light teak oil finish and regular oil/soap mopping for the traditional "nautical" look.
No, I don't think you'll have a problem with moisture since the concrete is not on ground level.
I don't doubt your workers are skilled at concrete work, but trying to accurately grade concrete or mortar to 1/8" in 12" will be nearly impossible. If they are off any at all - ANY at all - you will have a puddle of water.
That's just too tight a tolerance, unless you are going to come back and grind and polish and grind and polish. Maybe grinding equipment of such accuracy is available, but I'm not aware of it. The question then becomes how large and deep a puddle can you tolerate?
I worked on a government job back in the 80's and watched as the concrete finishing sub worked to get a slab "flat". Specs called for the concrete to be no more than 1/8" out of "flat" over a 12 foot span. They polished on that slab for weeks and weeks trying to meet spec - the entire slab looked like terrazzo when they finally got finished.
I agree - do not use galvanized steel.
If/when you do have a breach, it likely will be a very small breach, so you may not even know you have a breach until you start smelling mold - by then you have a real problem.
If it were me, I would explore the possibility of some sort of dry-air ventilation/moisture detection system. That way, everything is serviceable (and testable) from the top. That would give me positive control over the situation without relying solely on wood, gravity, water (leak) volume, and silicone.
An industrial controls engineer could easily design a simple, serviceable, fool-proof system - and I'll bet it would work better and cost less than trying to "finesse" your concrete.
Can you tell I don't like silicone? :)
Really appreciate your take Scott. I don't want to be a pain but is 1/8 of an inch in 1 foot really that exacting? Your story talks about 1/8 inch over 12 feet but you said in your message "(1/8" in 12")". Those little marks can get hard to see sometimes. I have had inspectors let me make crickets on flat roofs at that spec. without a problem. I wonder also did you get that in the case of a breach the water would be falling onto plastic sheeting not concrete (which is really "mortar" and much easier to slope and work with than "concrete"). Have you ever seen water sit on plastic like that? I kind of think a1/2" of drop in four feet... I think it's gonna flow. My tile guys routinely are sloping showers, bathroom floors going to floor drains at pitches like that. They have these aluminum (super straight) screeds up to 10 feet long that they float mortar with. They will sometimes hammer concrete nails into the mortar beds that they use as reference points, sometimes its a1"x2" dropped in the bed but you get my drift. I could always move slope up a little. Like I said before they're real good at masonry work and they average about $11.00 a day. I taught my tile guys to make they're mortar beds (walls and floors) to square up a bathroom first so there are no unsquare cuts in the tile work. Then I give them a bag of thin set and a serrated trowel and it turns out perfect. I can run perfect flat panel work over my guy’s walls without furring or needing to shim my furring. Most Thai's will float a 1" to 2" mortar bed with the tile included. The guys that do that "well", are genius but it's mostly about the economics. That is probably where my approach comes from. It's really almost 3rd world here. I have had to learn to adapt to working with what I got. That means problem solving with the materials and talent available. The first couple of years I started working here I had this reoccurring dream that only I new this secret little jungle road off the main road out of town that would open up into a clearing with a big beautiful Home Depot in the middle of it. I know I come off a little like "tell me my way works" but it comes down to what I got to work with. I can import but I have if it comes on a ship it will probably take to long or cost to much. I can air freight coatings and adhesives etc. I might just research that moisture detection system. When I first read that I thought I know a coconut moisture control engineer down at the beach. but I bet I could hook that all up via the internet and phone and air freight. Nice! Thanks Scott. Now if everybody’s still thinks that my galvanized furring is destined for failure, even when it's under plastic and anchored on the top of speed bump, what else would you use? Jim says I should fir it up with teak. I guess I don't have a problem with that because I don't think it's going to get wet being under the plastic. By the way Jim I don't think what your describing is a "floating floor" but I also don't think that we disagree to much (procedurally) except for (from what I know) you never rabbit or t&g teak boat decking. I've said this before, everything I know and have heard is it's always between 3/8" and 9/16" thick 2" wide and has a 1/8" gap between pieces for the caulking. The planks or strips are always square cut and this is because this is a well worked out formula for expansion and contraction. Deviate from this and do it at your own peril. The exterior portion of this project will be getting soaked daily. In rainy season we get allot of rain and it usually comes in the form of a monsoon which drives the rain horizontal and it's also next to a Jacuzzi. Also I think the glue is polyurethane not epoxy because it needs to move with the wood and no nails no screws. I think that you are right maybe it should be oil on the deck but what should the parts of the condo that don't get wet be finished with. Thanks again. I'm out.
If your mortar (concrete, plastic, whatever) is "out -of-flat" even one thousandth of an inch, then you will have a puddle that is one thousandth of an inch deep.
Regardless of the amount of slope, you will always have a puddle that is as deep as your surface is out-of-flat. Water will continue to build up behind the dam until it begins to spill over the dam, but it (the puddle) will always be as deep as the dam is high.
The steeper the slope, (chances are) the less surface area your puddle will have.
That's why I said, "how much puddle can you tolerate?".
I don't like the plastic idea because that creates another barrier that can fail - and you've already set it up for failure by penetrating it with screws. If you must use such a barrier, I'd suggest a PVC fabric roofing material such as IB makes (www.ibroof.com).
A combination of well-designed drainage, ventilation, moisture detection, and a removable, floating deck would be your best bet - you'll need as many things going for you as possible.