To Ply or not to Ply


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Old 01-07-19, 10:22 AM
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To Ply or not to Ply

Hi all,

I am doing a reno to a 1960s townhome. The home had 1” strip hardwood. The hardwood was installed the length of the rooms. And in the strips were run the length of the hallway; which just so happened to be opposite the rooms. I removed the old 1” strip hardwood flooring to find that there was 3/4” plank boards. The boards are about 3.5” in width. The planks are installed on a diagonal. I then realized that the 1” strips were installed perpendicular to the joists and that is why the hall is different to the rooms.

The ¾” plank subfloor is in good condition. I removed any nails from the strip hardwood. I then hammered in the old nails and screwed in every plank to the joists (joists are 16” OC) with 2.5” flooring screws (5000 screws). I will end up taking a floor sander to the planks because I found that there is gritty grime on some of the planks (most likely because of the plaster that was installed in the 1960s on the floor and ceiling). I also want to get rid of any high spots (wood chips) because of the nail removal from the 1” strips.

So I want to install either ¾” hardwood (4 or 5 inch wide) or engineered hardwood. Here are my concerns.

1) I want to run the new hardwood in one direction. The direction will be parallel to the joists in the rooms. Is that ok? Or should I put ply on top of the planks? If I should put down ply suggestions on thickness?

2) I really don’t want to put ply down because that will change the height from the bathroom. Also there is a guard rail along the stairs and code states that the rail must be 48” high from the floor. The guard rail is old wrought iron and secured really well into a joist. I am trying to avoid removing the guardrail if possible.

3) Also I have one closet that I want to run the same hardwood in but the closet is on a concrete slab rather than sub floor. There is vinyl tile on the slab currently. I can see that the tile is glued on with a black tar type adhesive. Can I glue the hardwood right on the tile?

Thanks.
 
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Old 01-07-19, 06:14 PM
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Running the flooring parallel to the joist on a single layer of subfloor runs the risk of your flooring having a "wave" to it. The joists are stationary, and sometimes there is a dip or deflection between the joists that cause the "Wave" to take effect. For that, it is always recommended that flooring be placed perpendicular to the joist system.

A large straight edge can guide you, but the deflection from body weight between the joists is something that you need to seriously consider. Single 3/4" on the diagonal, is the minimum standard for nail down. No guarantees on end result.
 
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Old 01-08-19, 04:17 AM
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Can I block from underneath

Thanks for the clarification. I understand now. Can I block between the joists from underneath say every 16 inches with a 2x8 to prevent the wave?

 
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Old 01-08-19, 08:22 AM
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I am doing a reno to a 1960s townhome.
You already have the wave, it's the slight depression that the sub flooring gets with time. Probably dont see it now but put down a nice shiny floor and it may pop out!

If, it's a floating engineering floor it would not necessarily have the same requirements to be installed perpendicular to the joists, but you need to check with the manufacturer!
 
 

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