We’ve run into a problem with Meranti (scenic Mahogany) on a deck applicatiion. We found out after the fact that the supplier recommended that it not be installed with hidden fastners ( we used Eb-Ty) nor be installed where it couldn’t ventilate, within 18 inches of grade. We’ve designed and built a deck that is waterproof below because we installed metal pans within the joist bays and a gutter to protect the screen patio below. Needless to say, we’ll be pulling up all the Meranti which swelled and cupped beyond belief and are looking for an alternative wood to use, possibly Ipe. Any ideas or wisdom.
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Ipe is good. You could also use red, white, or yellow cedar, Cambera or Mangaris (similar to Merenti), or a synthetic product like Trex, Tendura, or CorrectDeck.
I've used Merenti on several decks over EPDM, a comparable situation to yours, without a problem, though always with face nails or screws. Is there adequate pitch in your pans?
The pans do slope and hold no water. The suppier's rep suggested that we didn't have enough ventilation. How much did you gap your decking and did you apply a finish before installing? I'll be honest, after having been bitten once, we are seriously considering another wood, Ipe, which we will prefinish with Penofin and face screw with SS screws keeping a 1/4" gap for ventilation. Too much caution? This deck is really sweet; the gutter is hidden behind the steel support beam and both are covered with 1x12 fir. The ceiling of the screen patio below is beaded T&G and the screens are 20+ feet long and drop down out of a valence. As you can imagine, having the deck fail has been a real setback. Thanks for your input.
A few years ago, I spoke with a wood scientist about this stuff. He also recommended the ideal was a good 18' full free airflow under wood decking.He explained on Merrantii that it is not necessarilly a specific species, but more a family name. There are a couple dozen different trees ( I think from the Paciifc islands/ SE asia) that are aall inthe meranti family. Some are better than others for decks and you can end up with some higher percentages of summer wood v heart wood too. Basicly he was saying that it is an inconsistant product name. Buying 'meranti' is like buying 'pine'. There is a lot of variation. Same thing with camberra, but to a lesser degree. Camberra looks a lot like Ipe` but the diff can be like between red oak and white oak for exterior applications.I'll taake the IPE` thank you. It is also recommendded for 18" venting, but I have not had any instability with all I have iunstalled on sleepers over EPDM
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"always with face nails or screws"I am thinking the EBTYs may be the worst of the problem here. They were not strong enough to resist the forces of the wood swelling. Going to 1x4 instead of 1x6 wood increase the number of fasteners ( and strength of them overall) by aprox 50%Sealing all surfaces would reduce the amt of water absorbed, and consequently reduce the amt of tension placed on the fasteners.But face fastened means a chance to double the strength of the fastening system
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I just used Eb-Ty's for the first time, on a Trex deck. I didn't really like how the screw wanted to pull through the plastic.
All of the "mahogany" decking I've installed were 1x4's. I agree that the 6" boards are a big part of the problem here. Ipe is fine in a 5/4 x 6, but Merenti is too weak a wood (sorry, "group of wood species ;-) and too prone to movement to handle one Eb-ty screw as a fastener.
I've never seen pans installed between joists, but I find the idea very interesting. Have you ever tried that approach before?
Do you happen to have any pictures?
I've enclosed some pictures of the pans, the failing meranti, and copper gutter. The deck does slope and the pans also slope to the copper gutter which is hidden next to the supporting steel beam. I'm really interested in knowing if Ipe can be installed in a situation with poor ventilation from below. It sounds like it can.
Thanks for posting the pics. The deck must have looked great before the boards went wild -- must be very frustrating. Let us know how the fixes turn out.
Ragnar
Edited 7/9/2007 12:45 am ET by Ragnar17
Is the Meranti you use from Indonesia? or from elsewhere.
Is it treated at all?
Meranti is used here in Oz by some less caring Builders for windows, it rots and is generally considered to be a cheap product. It also is used for architraves etc internally.
We do not use any timber from Indo as their forestry practices are deeply corrupted at the expenses of the climate, the local people and the fauna.
Maybe meranti is a generic term for other similar looking timbers?cheers,
Johnhttp://www.johnwalkerbuilders.com
I have done Ipe, Massarunduba, Southern Pine treated with penofin, and long leaf pine painted over sleepers and EPDM-Have not had any problems. Are your pans draining well and do you have any pitch on the deck itself?
Bruce
I did Ipe on Ipe sleepers resting directly on a rubber roof over a year ago. No problems. I did put anchor seal on the end grain to prevent endgrain checking.
Is Anchor seal the wax like product you apply to the end grain? We'll be precoating the Ipe with Penofin and applying a wax type product to the end grain as well as attaching the decking with stainless steel screws. Thanks for thhe information and photo.
Here is a deck I did a couple of years ago. It is meranti, pre-coated with Penofin Gold Label and Anchor Seal applied to end grains. Has held up perfectly well in a NE coastal environment.http://forums.taunton.com/tp-breaktime/messages?msg=90305.8
fastener type?
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Yes.http://www.internetlumber.com/lumber-products/DECK-ANCHOR?gclid=CObu4tXOlY0CFQIpFQodTWYA5w
Here is what I see from the photos-
1x4 is a faar better size for all wood decking becuase you have a better ratio oif spaces to wood to handle swelling and provide ventilation.
That outside corner makes it very clear that the wood has absorbed lots of water and swelled and moved across the deck. This has put way too much tension on the fasteners. This is not the first I have heard of theEBTY system failing. Having never used it, I can't be too detailed about that, but it is certain the wood swelling is the major primary problem. The EBTYs may also have not been adequatly fastened.
Two more problems, one design and one exeution.
The design layout has this decking parrallel to the house. That means that all the water that lands on the deccking has to fall over the edge of it, into the pans and then drain out from under. With designs that allow water to follow the deck bord off for drainage by running the decking perpendicular to the house, about 85% of the water will surface drain and have less opportunity to soak into the wood.
In exeution - the decking should have been treated on all four sides before installation to resist moisture. Penofin is a good choice for this.
Alll the tropiccal deck wood sales seems to suggest that it is a forever wood since it resists rot. But what most folks seem to ignore is that even tho it will not rot, there are other degrading influencces on the wood. The penefin can help prevent that.
I also wonder how much more water is sucked into the wood via the slots cut for the EBTYs. Most of the tropical woods sellers recommend the latex treatement for end sealer at the cuts. A slot in the edge exposes a lot of end grain so it stands to reason that it should be sealed as well.
If you plan to change type of wood, I have had excellent results for years now with Ipe` on sleepers over EPDM with face screws. Some have been oiled and somehave never been treated.
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Taunton University of Knowledge FHB Campus at Breaktime.
where ...
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