subfloor thickness and floor height differences

Reply

  #1  
Old 04-06-12, 11:43 AM
Member
Thread Starter
Join Date: Jan 2008
Location: Canada
Posts: 31
Lightbulb subfloor thickness and floor height differences

Starting a new flooring project carpet -> engineered hardwood on an upper floor of the house. This is me thinking out loud .. What I'm missing is experience to tell which aspects are more important than others.

The goal is to replace carpet with a floating installation of 3mm high quality felt underlayment and (3/8") 9.5mm engineered hardwood flooring

What I have:
  • (19/32") 15mm OSB exterior grade construction sheathing subfloor
  • Existing (3/4") 19mm hardwood in the largest room on the floor - that is staying
  • Existing carpet in other rooms - to replace

Flooring manufacturer Installation recommendation:
  1. Install perpendicular to floor joists
  2. If installing parallel to joists - minimum additional 3/8" underlayment to stiffen the subfloor
  3. Panel direction parallel with longest wall
  4. Allow 1/2" expansion around all vertical obstructions
  5. Min 23/32" (18mm) OSB subfloor thickness (I have a 15mm OSB - verified)

Overall there would be a (1/4") 6.5mm thickness difference between the hardwood-finished room and the rest of the floor, after carpet is replaced with new engineered flooring and the felt underlayment.

The two main options that emerge are:
A. Do not equalize floor thickness; install perpendicular to floor joists for strength and use T-molding 1/4" offset transition strips where applicable. This changes the panel direction at the threshold to the hardwood room and also the direction and floor thickness at the first step of the stairs.

B. Equalize floor thickness by laying 1/4" OSB or plywood underlayment everywhere the carpet was. Install flooring parallel to floor joists. This preserves the wood panel direction everywhere. Rooms are almost square so this would not clash with the "longest wall direction" rule.


Option B increases cost slightly and almost addresses less-than adequate subfloor thickness and direction issues. Is that the better option? is 1/4 floor height difference a tripping hazard, especially at the stairs?

thanks
 
Sponsored Links
  #2  
Old 04-06-12, 01:04 PM
jatco's Avatar
Member
Join Date: Mar 2004
Location: Vancouver, BC
Posts: 1,045
Hi...
I would go w/your option B - for the reasons you stated...and stain to match. That's what I would do in this situation if I had to.
 
  #3  
Old 04-07-12, 11:19 AM
Member
Thread Starter
Join Date: Jan 2008
Location: Canada
Posts: 31
Thanks i guess i answered the question myself :-)
 
  #4  
Old 04-07-12, 11:36 AM
jatco's Avatar
Member
Join Date: Mar 2004
Location: Vancouver, BC
Posts: 1,045
You're welcome, - no worries..
It's always good to bounce it off others, to confirm it ..!!
Good luck..and let us know how it goes..!
 
  #5  
Old 04-10-12, 05:43 PM
Member
Thread Starter
Join Date: Jan 2008
Location: Canada
Posts: 31
Post Update

All the materials are purchased .. 1/4" OSB, wood glue for the engineered floor, subfloor glue for the underlayment, subfloor screws.

Carpet's off in one of the rooms and no surprises there.

The 15mm OSB subfloor is noticeably springy - not unstable but springy. Expected a nightmare pulling out carpet / foam underlayment staples but they were very short stables and not very many. Carpet strips were out in 5 minutes.

Note to self - no point in fixing walls where old baseboard was .. just get taller replacement baseboard. The alternative would be to prime the drywall, fix any holes with drywall mud and make a uniform surface where the baseboard was .. then paint. No thanks.



Researched underlayment candidates: plywood (and luan) vs OSB. General takeaways:

Non-structural 1/4" OSB can be 1/3 the price of cheapest plywood - CAD5.80
Specialized underlayment (sanded plywood / luan / lauan / mahogany board) only makes sense for installations which require smoothness - like for vinyl where any imperfections will show. Those materials cost CAD25-30.
Plywood technically stiffer but only marginally (10%).
OSB remains flatter and its strength is uniform (no warping like plywood, and no soft spots)
Plywood behaves better with moisture; floating installations over OSB mitigate that with a moisture barrier underlayment (?). I have no idea what mitigates that in the kitchen and bathroom where tiles are installed over the same 15mm OSB subfloor. Damn new building standards.
OSB does not hold nails anywhere near as well as plywood
OSB underlayment can be glued to subfloor and nailed/screwed into joists, edge joints offset to subfloor edge joints
"modern" OSB resistance to water is noticeable, except at edges (because resins are "waterproof" and OSB also contains wax)
Interesting but useless fact (to me) - OSB is stronger than plywood when heated (may be a reason to use in roofs?)

If you're reading this, take the list as research notes .. I am not a pro - research is all I can rely on, since I have no experience.
 
  #6  
Old 04-10-12, 08:53 PM
jatco's Avatar
Member
Join Date: Mar 2004
Location: Vancouver, BC
Posts: 1,045
Great update.. Lots of info to take in and absorb..!!
My subfloor preference is ply..but K3/particale board is frequently used for such applications.. (using it just recently on a job..) .. -OSB will be fine,, but not my preference for subfloor.y
Either way, - Dont skimp on the screws..imo. I always go thru the original flooring and pound in the original nails etc.. then I always glue at joints and Zig-Zag glue lines thru the field ..just because...!!
.
Base boards.. I agree, just up the height as needed, to cover the x-caulk lines. I usually skim off some heavy caulking with an Olfa blade, to try and make the walls smoother, for the new base install...(that's just me...!).
Other than that, at this point, it looks like you have it under control....!!
Look foward to more info...
It should turn out Fabulous...........!
 
  #7  
Old 04-12-12, 07:31 PM
Member
Thread Starter
Join Date: Jan 2008
Location: Canada
Posts: 31
Talking underlayment almost finished

Thanks. Yes.. things are working out. Tomorrow I'm finishing the install of underlayment .. 14 4x8 sheets overall. Then the hardwood.

OSB on top of existing OSB seems fine. It is stable with a 15mm + 6.2mm combination, glued and screwed. Premium construction glue is worth it IMO.
Double-thread flooring screws are grabbing OSB even when not on top of a joist. OSB surface is coming apart 20% of the time, when the screw is driven in. Looks messy but probably not a problem if flattened or sanded afterwards. Also noticed that panel joints on existing subfloor were sanded when installed .. to flatten uneven panel edges. This is where plywood would shine.

I completely agree with baseboard cleanup.. figured out that caulking left from the top of old baseboard needs to be scraped/cut off with a blade at a small angle to the wall. Works nicely and leaves a flat surface without damaging drywall.

The biggest pain in the back was removing carpet from the stairs. This wasn't planned but with clouds of dust from the carpet everywhere it seemed efficient to just continue on. I have stair veneers to install. On stair surfaces the carpet's stapled using a million small staples and the wood uset to make stair treads is much harder than OSB .. it is a struggle to get the staples out. 16 stairs = 3-4 hours of work just to get all the carpet staples off .. that's as long as taking the carpet off 500 sq ft of floor. A good set of pliers (linesman and needlenose at least) helps.
 
  #8  
Old 04-12-12, 07:44 PM
jatco's Avatar
Member
Join Date: Mar 2004
Location: Vancouver, BC
Posts: 1,045
I usually clean off the top edge with an Olfa blade, tight angle to the top edge..and then give an overall sanding, to the top and edges of base. Makes for a better reinstall.
Sounds like a challange with the x-carpeting.. Yikes...!!
Sounds like you have it under control...!
 
  #9  
Old 04-12-12, 09:13 PM
Join Date: Nov 2000
Location: Austin, TX
Posts: 5,074
If you are going to do the staircase leading up to your installation area, you better do the staircase first, so the top step up into the 2nd floor is square and the starting place for the start of the upstairs, or where all the planning will take place, depending on direction of the flooring and step orientation. (Butting to, or running with)
 
  #10  
Old 04-12-12, 09:32 PM
Member
Thread Starter
Join Date: Jan 2008
Location: Canada
Posts: 31
Thanks. I've mulled over the where to start question for a bit and decided to start in the bedrooms. If I get in trouble in a big way I'll use thresholds in doorways, but with measuring as I go and keeping the lines true I should be fine to meet in the hallway aligned. Picture a floor plan with two bedrooms side by side at the top, adjoined to a hallway at the bottom, continuing downwards, with the staircase at the right bottom corner going down parallel to the hallway axis.

The hardwood will butt with the top stair nosing (parallel to it) and I can trim the top stair tread part as needed. Planned to keep it narrower than a regular tread .. ie 4-6" instead of the full 10-12". The hardwood is 5" planks.

I might post a photo if it goes this far tomorrow.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
'