I have a deck on the house that is currently nominal 2x4 of various species. (the previous owners had no taste). I want to replace the surface with Ipe wood. It comes as nominal 5/4 x 6 which is a better look IMO. The problem is how to make up for the smaller dimension?

  • Seriously, is ripping a bunch of 1/2 inch strips the professional way to go?
  • Would you paint the strips to keep moisture out?
  • I suppose I could use some of the PT that we pull up to make this shim, right?

A few edits to address the questions in the comments.

  • Yes i want the good wood called Ipe.
  • no the concern is not the stability of the floor, the joists are 24" or less
  • the concern is how it looks / behaves under the threshold of the slider doors and where the siding meets the deck.
  • yes I have been formatting the paragraph to look / read better, but it just keeps clumping it all together. uurgh...

A couple things the past few days....

2x Ipe is cost prohibitive, double the cost of the 5/4 Ipe. However Ipe is the way to go. Therefore we're thinking of putting a 1/2 inch shim on joists or putting a 'sister' joist that is 1/2 inch proud. We need the decking level to be the same after the thinner board. If there were a gap or even a filler bit under the doors and siding it would look like a mistake. There are 12 doors that meet the decking.

One pro suggested rubber flashing to help hold the 1/2" shim in place and bonus shed the water. Explain again why you wouldn't do this? How else to support doors?enter image description here

  • 2
    I'm not sure I follow your question - a quick sketch might help. Are you saying the current decking is 2x4 (laid on the 4" side, I presume), and that you're replacing it with the 5/4x6? Are you concerned about the difference in wood thickness between the 1.75" thick 2x4 and the 1.25" thick Ipe? If so, there's no concern at all - 5/4" lumber is quite sufficient for decking. The only issue might be the step distance from the deck into the house. Unless that distance is already at the max for comfort/code, the additional 1/2" step may take a day to get used to...
    – FreeMan
    May 22, 2020 at 13:06
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    ... but is otherwise not an issue at all. If I've totally misunderstood your question, please edit to provide more detail. (Also, some formatting instead of a single block of text would help readability.)
    – FreeMan
    May 22, 2020 at 13:07
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    Yes, why is this a concern? The only issue should really be at your door threshold, and there you can use a shim if it needs support.
    – isherwood
    May 22, 2020 at 13:11
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    To ans your concern about the exposed 1/2" where it meet the siding, Just add a molding strip similar to a baseboard on interior walls. It could be the IPE board cut to a 2" or 3" width. I would not add stripping to the supporting joist to bring it up a 1/2". Jun 4, 2020 at 23:13
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    Ah, adding new joists at 90° to the existing ones will solve all your problems. The alternative solution (if you were going to keep the decking in its current orientation) would be to simply replace the trim boards with taller trim! After the installation, nobody but you (and the us here:) would know that the current trim was taller than the previous trim, and the step height doesn't look like it would be an issue in the least. after 2 or 3 days, you'd quit tripping up the step because you'd be used to the new height and all would be good!
    – FreeMan
    Jun 15, 2020 at 15:26

1 Answer 1


I would stay with 2 X lumber instead of 5/4 "decking". that will solve your dimension problem . Regular 2 X lumber is twice as strong, twice as stiff and lasts much longer, compared to 5/4 decking. My deck is 2 X 6 , 25 years old and I have made a few repairs. The community pool has some 5/4 decking ,it has been replaced twice in that same time and does not look so good right now. More objectively ,the strength is proportional to the cube of the thickness; that cube is 3.38 for 2 X lumber and for 5/4 the cube is 1.95, so not quite 2 : 1 difference. Update- I went to the pool today ,5/ 23, a new deck had been put on during the winter ,so 3 decks in about 25 years. But, this time someone got smart and put in 2 X lumber instead of 5/4.

  • Deleted earlier comment where I said ipe was stiffer than softwoods... I went to the sagulator and discovered that 5/4 ipe is slightly more sag-y than 2x pine or redwood. May 22, 2020 at 22:38
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    "Regular 2 X lumber is twice as strong, twice as stiff and lasts much longer" I'm skeptical. It looks like ipe has a modulus of rupture about 2.5x that of pine and is substantially more rot resistant. So even with the extra 1/4" of thickness for a 2x piece the ipe is still going to be stronger (1.5^3/1.25^3 = 1.73 [in favor of the pine] but 177.0 MPa/71.0 MPa = 2.5 [in favor of ipe]). It looks like ipe still comes out ahead.
    – Brad
    Jun 15, 2020 at 17:15
  • I was comparing pine to pine of different thickness . Ipe looks like a very strong very expensive wood. Jun 15, 2020 at 19:46

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