Hey everyone, I’m new to this forum
Have a question that I hope you can help me with. We are putting in 3/4 inch oak hardwood in our house. I have 1 and 1/2 inch tongue and grove subfloor not plywood. The floor joists are on 4 foot centers. I haven’t been able to get an answer to my question is that a suitable floor to install over? Any help would be appreciated
Thanks

Yes the inch and a half T&G planks over post and beam framing is good for laying any type of hardwood floor. The planks are long and go over two beams so there is a type of cantilever support. There should never be more than four butt-joints in a row in the sub-floor system. If someone makes a patch or cuts through the sub-floor for under floor access, like for the plumber to get to pipes easily, then extra framing is required for support where more than four planks are cut for the access hole. In some cases where there is extra load, like a kitchen cabinet with heavy counters extra support may be needed.
The 5 inch width planks are going to be better than the seven inch width.
Go across the planks when laying the floor if possible. The planks are not kiln dried when they are laid so they will shrink, sometimes so much that the T&G does not touch like it needs to be. A two by six across the planks under the sub- floor will be where the planks can be fastened together.
Set nails with a quarter inch punch before any sanding when flattening the floor before laying hardwood on top. Low ares can be built up with thick sandpaper as necessary to get within a quarter inch in six feet, or so.

Thank you for the information it is very helpful. I assume if the floor is in bad shape it will be ok to install 1/2 ply over the T&G?

If you want to lay half inch ply over the existing sub-floor you ought to make sure that any floor flattening is done first. Use the underlayment nailing schedule of 6 inches on perimeter and 8 inches in field, and offset the joints of plywood sheets.

That being the case is there any advantage to installing the plywood. Having never installed hardwood floors before I want to make sure I do it correctly. Would you install the plywood or just go over the 1 1/2 inch sub floor.
Thanks again for all your assistance

I would go over the sub-floor after I checked it for integrity. It will support a 3/4 inch thick hardwood floor. Thinner 5/16th inch thick parquet would need an underlayment depending on the design. If you like to go the same direction as the sub-floor is laid, a plywood is recommended.

Thanks for all your help