ᐅ Warped Decking Boards – Are They Usable?

Hello,

My wife wants a wooden deck suitable for barefoot use, so we chose Yellow Balau.

The delivery arrived yesterday: out of 29 boards, each 3.97 meters (13 feet) long, 2 are quite strongly curved in the middle, almost bow-shaped. The deviation is about 4-5 centimeters (1.5-2 inches). A few others are not completely straight either, but to my untrained eye, they are acceptable. A 5% defect rate is allowed, the supplier insists on this and also emphasizes that “wood is a natural material.”

Question: Is it possible to straighten these curved boards for use as decking? I have read something about using spacers plus a ratchet strap and screwing them down. Or are these two boards unusable?

Addition: The floorboards are not warped upwards, but curved sideways.

With "5% defects," the supplier is out of the acceptable range in 2 out of 29 cases, which is nearly 7%. Talk to them. I would not use the floorboards on the terrace, as they are defective.

The 5% does not refer to the quantity but to the deviation per meter. That means 5cm (2 inches) per meter. We had a similar case with our Garapa terrace. It was about 10cm (4 inches) bent over 4.5m (15 feet). However, it was still possible to manage with tension straps and so on.

OK, so how do you handle the ratchet straps? Do you attach one end to a straight, already screwed-down board with the correct spacing, then tighten and screw it down bit by bit?

Is there an instruction manual for that?

I complained to the supplier but nothing came of it. Then I mentioned the return policy, which allows returns within one more week.
Would you go ahead with that, or is this kind of thing standard?

AndreasPlü schrieb:
OK, and how do you handle the tension straps?

Since I just went through this with several decking boards:
Laying the whole thing goes faster, is easier, and lasts longer if you use plastic spacers between the supporting joists and the decking boards. They only cost a few euros and are worth the money. Depending on the wood, spacers are 4 or 7 mm (0.16 or 0.28 inches) wide and about 6 mm (0.24 inches) high. This ensures a consistent gap so that no wood rests directly on wood, preventing water from soaking in or staying damp long-term.

Start with several as straight as possible boards. Even if boards look straight at first, use clamp straps or C-clamps (not too tight) to pull the board you are about to fasten towards the already screwed ones, pre-drill holes, and screw down firmly. Move the clamps along as you go. Begin at one end, screw, reposition the clamp, screw again, and so on. The straighter the board, the less often you need to reposition the clamp. Usually, moving it every 3–4 supporting joists is enough. Even if it’s not obvious at first glance, most boards are warped a few millimeters. This is hard to avoid.

If you don’t have a drilling guide, it’s easy to make one to ensure that holes are always centered on the wood and evenly spaced: Build a "sled" from about 30 cm (12 inches) of leftover decking board or another piece of wood plus two 10–15 cm (4–6 inches) pieces of construction wood. Attach the pieces lengthwise to the left and right at the bottom of the decking piece so that the supporting joist fits exactly in between, with the wood pieces standing parallel and aligned flush. Place this sled on the substructure so that the rest of the deck piece rests on the board to be drilled and aligned. Drill two holes in the sled exactly where the screws will go later—centered between the wood pieces and about 2 cm (0.8 inches) from the board edge. Now you can conveniently place the sled, pre-drill through the holes, and all screws will be perfectly aligned and never too far in or out.

For warped or bent boards, like your two problematic ones, proceed as usual but initially position them so they bend away from the already fixed boards. Then apply the clamps (typically no more than two clamps are needed), tighten them until the next screw point reaches the correct distance from the fixed boards, then move along to the end. It’s best to clamp as close to the supporting joists as possible; otherwise, the fixed boards can temporarily bend around the clamp’s pressure point. The wood doesn’t suffer much from this, and the tension gradually releases over time.

If a board is twisted in a screw-like way, do the same but make sure it lies so that the twist turns downward on the side facing the fixed boards. This way, the board always rests on the spacer and isn’t pulled down by the screw later. Otherwise, the spacer can chip.

Good luck!