Flattening the substrate can be challenging. I would let the new installer do it. There are various ways, especially if you are going to float the flooring and not attach it to the substrate.

Sorry, I missed something somewhere in this thread. If you have a conventional joist and plywood sub-floor in place, what is the purpose of the strapping you propose to align over the joists?

HI guys,

Help! please. I am meeting with another installer tomorrow. A man that has been in the business of laying engineered and hardwood floors for over 25yrs. Hopeing he can give me an objective opinion. I sure hope he knows someone who can fix this mess for me if he's not capable of doing it himself.

Right now I'm not sure what the correct solution to the problem is. All I know is it has to be fixed before the engineered flooring can be installed. Thank god it's not a 3/4" hardwood floor that's being installed. So the subfloor doesn't have to be dead flat. It's being floated.

I have no idea whether or not screwing down sheets of 4'X8'
strapping and shimming over the origional subfloor is the right approach. The bungalow is 35yrs old. The 1/2" thick plywood subfloor is screwed to the joists 16" on center. Pretty sure they are 16" oc. I'm assuming they are. The floor in the livingroom (above an open basement) an unfinished basement. The floor slopes in some areas and is out by as much as 1/2" in one area. (the installer who came up on Monday tested only one are of the floor. I guess throwing marbels on the floor told him all he needed to know. The high spot is approx. 2 feet in front of the fireplace. Nobody has taken a level to the subfloor to mark where the low spots are. If you were inspecting that floor wouldn't you take your level and move it all over the floor in a systematic way checking for flatness and marking with a pencil all the low areas.

Most of the articles I've read online usually talk about screwing down a 5/8" or 3/4" plywood Underlayment directly to the subfloor as a way to level the flooring. They also mentioned that you never want to touch the subfloor (the plywood that is directly attached to the joists) unless you have to. BUT what happens if the flooroing is out by 1/2"? Would screwing down a sheet of 5/8" plywood over the unlevel subfloor make it level enough so that you could lay the engineered flooring? That's what I need to know.

I have heard of strapping a basement floor.. where you nail the strapping directly down to the concrete using concrete nails and wood shims. and then you just nail the plywood over the strapping. That may be ok for a basement floor But I'm getting the impression that this is not the correct way to level up an out-of-level livingroom floor. Yes/No

The only thing I know for sure is that floor leveller won't work for a floor that has spots that are out more than 3/16" over an 8' radius. That's what the man at the flooring place told me. \


Wanda

Simply putting a layer of plywood over an irregular sub-floor only reduces headspace, it does nothing to change the level of flatness.
Your comment about a floating floor not needing the same degree of flatness is opposite to the reality. I can bend a nail down floor over any subfloor, but a float install requires flatness to perform properly. This is not an aesthetic thing, a float floor will fail unless it sits on a flat surface.

Amen, Dennis. Naildown installs are FAR more forgiving. Wanda, if you float over the floor, it MUST be flat to within 3/16" per 8-10' span....if not, you're looking at some movement and squeaking/popping at the least...worst case, a failure of the t&g and separation occuring between planks.

Hi guys,

The installer came up to check out the flooring this morning. Seems it is not such a mess after all (at least according to him) It may not be perfectly level but what floor ever is in an older home which has had time to settle over the yrs. He has the proper tools to do the job. (Spotnail Stapler) which is the tool of choice for engineered flooring. Stapling it down would be better than floating the floor. He pointed out the mistakes the other installer had made. Improper size fasteners and improper tool. A brad nailer is not recommened and the nails they used were too small and too long. The pattern of the floor is also not right. (stepping effect. Seams lining up) This time the floor will be installed perpendicular to the joists. (across the width of the floor and not with the length of the room).

He said I could just leave what's down on the floor perhaps put a few more shims underneath the furring. NO need to lay 5/8" plywood on top of what I have down. I have to trust he knows what he's talking about. He's been in the business of laying hardwood for over 25 yrs. He has laid floors in old homes not just newly contructed homes. He walked all over the floor and declared it perfectly acceptable for laying engineered hardwood. While he was there he also checked the wood for moisture content and the subfloor as well. Everything is fine 12% MC in the subfloor 8% in the wood itself.

While he was up there he noticed the vinyl wasn't put down correctly. The seams in the plywood should have been sealed and an 3/8" underlayment should have been installed before the vinyl was laid.

Now that I know putting plywood on top of a warped/wavy subfloor would only lower the height of my ceiling..How would you go about leveling the out-of-level floor if you wanted to lay click and lock type flooring? I'm not going to but what if.. just curious

Wanda

There are so many ways to accomplish that. Some are better than others, all are acceptable. Here is the way my company does it if we are looking for an economical solution.
We will sand down high areas using an out of general service edger and 12 - 24 grit paper. We then pack low areas, usually with varying thicknesses of cork underlay.
To put it into financial perspective (and that is what most concerns a great deal of our clients) a 300 square foot room costs out about $1.00 to $1.50 per foot. for this levelling.
There are more politically correct ways to achieve a flat subfloor but this works for us.

If you are floating the floor why not just use a self leveling compound? the product might cost a little more but should save time in labor costs.
Depending on how big the job is that is what I usually do.

Hi,

I was told self levelling compound wouldn't work it's more or less used as a shim coat. when you are 1/2" out that is not the best solution.


The cork might work but there is nobody I know who would do it that way. They are telling me to rip up what is there and put down 5/8" TG plywood. but like someone else said earlier just putting plywood on top of an out of level floor isn't going to work. It's just going to "lower" your ceiling.

wanda

Most of the leveling compounds say they can be poured up to an inch, and that is per coat just make sure you use the recommended primer before each coat including the first. If I have a really deep void I will fill with either various pieces of wood to fill most of the void then use the self leveler.