Replacing whole house subfloor

Reply

  #1  
Old 11-23-13, 06:46 AM
Member
Thread Starter
Join Date: Nov 2013
Posts: 6
Replacing whole house subfloor

Hi all,

Just found the forum today and it looks great!

My fiance and i recently moved into a house that her parents had built. While the house in general is constructed superbly, a critical issue was missed... water runoff. Rainwater was pooling in front of the house and it has in essence kept the crawlspace at near 100% humidity for the past 15 yrs and that has rotted the subfloor.

When we discovered this we had the crawlspace encapsulated and french drains installed. I'm not working on replacing the subfloor and just want to get a 2nd opinion (or three!) on if i am headed in the right direction.

The original subfloor is 3/4" T&G laid normal to the joists with a layer of tar paper and then a 2nd layer of 3/4" T&G laid normal to it (parallel to joists).
Joists 2x6 with 24" oc, 6' oc between beams.

My plan so far is to remove the old subfloor using a toe-kick saw right along the sheetrock (as can be seen in the pics of the floor i've removed so far), plane the joists to remove glue, add in PT 2x6 joists on the wall that runs parallel to the joists (50/50 under the old and new subfloors, ends up spaced about 3" from the outermost joist) and PT 2x4 blocking on the walls running perpendicular to the joists and interior walls. I'll be using 3/4" Advantech to replace the subfloor.

Is this a good route to go, any suggestions, pitfalls or other issues? The internet is sorely lacking on large scale subfloor replacements, it only talks about bathrooms. I want to make sure I'm not compromising the structure of the house.
 
Attached Images     
Sponsored Links
  #2  
Old 11-23-13, 07:21 AM
Banned. Rule And/Or Policy Violation
Join Date: Apr 2013
Location: USA
Posts: 4,297
Have you or did you have someone come in and treat all that exposed limber? Really needed to be treated with Boracare.
No way would I be using pressure treated for joist. It's going to at some point dry out and cause issues as it shrinks. You would have to use all ACQ fasteners, about doubling the cost.
Only having 2 X 6's for joist I'd double them all up.
I would add hurricane ties where the joist rest on that beam to keep things from moving.
If that's a sliding door I see in one of those pictures I would have removed it and ran the subflooring under it and reflashed it.
A planner will be destroyed if you try to remove that old glue with it. Just use a sawsall laying flat. Rubbing the blade first with some bar soap will help keep the glue from sticking.
 
  #3  
Old 11-23-13, 07:28 AM
Member
Join Date: Oct 2008
Location: New England
Posts: 9,994
Ouch, that's a major project as you already know. I'll just welcome you to the forum, welcome, and add some comments. Some of the better carpenters will chime in on structural issues.

Lots of glue and galvanized or other pt compatible nails. You will need to ask about screws, code and IMO, they often break. Try pulling out a galvanized nail after it has been in place for 5 years and you will like them.

Since I have never replaced an entire subfloor, only small sections, I'll let the real pros comment.

Bud

Joe beat me
 

Last edited by Bud9051; 11-23-13 at 07:29 AM. Reason: slow
  #4  
Old 11-23-13, 07:42 AM
Banned. Rule And/Or Policy Violation
Join Date: Apr 2013
Location: USA
Posts: 4,297
Regular electro plated galvanized nails are not ACQ approved, you would need hot dipped.
If it does not say ACQ approved I would not use them. There just going to rust off.
 
  #5  
Old 11-23-13, 08:20 AM
Member
Join Date: Oct 2008
Location: New England
Posts: 9,994
Thanks Joe. The hot dipped ones seem to have a texture to them as well that makes them hold better.

But eliminating the pt is probably the best for reasons you stated.

Bud
 
  #6  
Old 11-23-13, 05:36 PM
BridgeMan45's Avatar
Member
Join Date: Oct 2011
Location: USA
Posts: 3,196
As already suggested, don't use a planer to true up the tops of the joists. A 4" angle grinder with medium or coarse wheel will work just fine--just hold it almost parallel to the joist tops and slowly work it back and forth over the crud you're taking off, slightly lifting the leading edge (just like floating fresh concrete). A light touch is all it takes, as leaving it in any one place too long will create gouges that you don't want or need.
 
  #7  
Old 11-23-13, 07:12 PM
Member
Join Date: Mar 2013
Location: USA
Posts: 457
As said already, add blocking (2x4 flat) between joists to tie old/new plywood together, toe-nail through edge of old flooring. Add caulking to stop any moisture (from crawlspace) between plywood edges there- on blocking. Lay both layers perpendicular to joists, stagger end joints on different joists. Stagger running seam (long edge) at least 6" away from one below. Glue T&G at groove for optimum strength. Nail from one end to other end- usually start from last sheet laid, end- so sheet will be flat and in full contact with joist glue while you stand on it. If sheets are stored standing on edge, they may easily cup then when laid and if fastened from each end toward middle- it won't settle down tight and later squeak.

Gary
 
  #8  
Old 11-23-13, 08:35 PM
Member
Thread Starter
Join Date: Nov 2013
Posts: 6
Thanks for the replies, sounds like moving away from PT wood was worth the question alone!

So as I understand, i need to spray all of the existing joists (and new untreated joists too?) with the boracare product, sister all joists in the house and use hurricane straps, i assume the strap is tied to the new sister? Or on both sides? Do i need to place hurricane straps on all joist to beam joints or just the perimeter beams?

can you help me with an explanation on why the sliding door needs removed? I'm okay with it, but I'm meeting some serious resistance to removing it from my fiance; she is prodding the floor and saying it is sturdy, but it seems to me that it is a long term risk to not replace the subfloor under it.

2x4 laid flat for blocking seems acceptable to me on interior walls, is that okay to do on the perimeter/structural too?

I attached today's progress for the kitchen/dining. i moved my first 15 sheets of advantech into the house on the joists to help keep them dry, they have always been stored flat. i've got a pallet (45 sheets) coming on Tuesday, and it'll be stored out in my metal building till i get the rest of the floors up. i figure if i cart the sheets i plan to use a week or two ahead into the house it will give them time to acclimate.
 
Attached Images   
  #9  
Old 11-24-13, 04:10 AM
Banned. Rule And/Or Policy Violation
Join Date: Apr 2013
Location: USA
Posts: 4,297
Some things I missed.
#1, 2 X 6's are undersized for floor joist and 24" spacing makes it even worst.
Could you get away with not doing it, yes, will the floor be wavy, most likely if it's not done.
If it was mine I would add another joist between each one.
The ties need to be where the joist cross that center beam.
Make sure the joist are crowned up.
Pull a string across the joist and a long level to check for low or high places before installing the ties. Main reason is I have no faith in a solid beam being used like that. They tend to sag, twist along it's length. You may need to do some shimming or planning to get the floor flat.
If that slider does not go to the outside I guess you could get away with it staying in place. Reason I suggested removing it so there would be a solid, flat, non flexing, subfloor under it so there would not be issues with the roller dragging and loosing as the doors opening and closing from a wavy floor.
It would be interesting to see a picture of the outside of the porch.
One of the biggest mistakes when I see this kind of damage was caused from someone building a stoop, deck, patio right up against the side of the house and doing it wrong.
A few simple rules that a lot of builders do not follow and DIY's always do wrong for the most part is, it should not be even with any door opening thresholds!
Sheathing and siding should not have been within 6" of any solid surface.
Wall needed to be water proofed to below the foundation before building anything in contact with the side of the house.
I was the guy that got called in years later to deal with all the old building mistakes and have seen time and time again just how much damage can be done.

What those pipe looking things coming out of the wall?
 
  #10  
Old 11-24-13, 07:18 AM
Member
Thread Starter
Join Date: Nov 2013
Posts: 6
Hi Joe,

the beams/piers are set on 6' centers when normal to the joist, and parallel to the joists its on 10' centers. The floor is L/560 (or L/330 if assuming rotten joists) when accounting for the supports at 6'.

the odd looking pipes are for a small hot water heater that was set under the counter for the sink and dishwasher. there are sink pipes a bit further down the wall.

-Do the joists need to be sistered and set to 12" centers or just one or the other?
-im not sure i understand the comments on sheathing/siding being 6" from a solid surface.
 
Attached Images      
  #11  
Old 11-24-13, 07:50 AM
Member
Join Date: Oct 2008
Location: New England
Posts: 9,994
If you have never worked with T&G material, it can be difficult. My last project was 150 sheets on the roof and another 50 on inside floors. You will want to check every tongue and groove for buggers. Damage and imperfections that don't allow them to fit together properly will be discovered at the most inconvenient times. And when they need a little help, don't smack them with a hammer. Use two scraps of sacrificial board one tongue and the other groove and tap on them. If more persuasion is needed, use a long sacrificial board and a piece of 2x6. Hold one end of the 2x6 in contact while swinging in the other end (with force) to make contact along the full length. If you seat the T&G furthest away from the butt ends, it will close the gap at the butt when you seat that end.

It would take less time to show you than describe it here, but that's the best I can do for now.

I used a ton of construction adhesive and although it dries slow, it holds well once it hardens. Buy one of the larger caulking guns to hold the contractor size tubes, far less expensive. If you glue all seams as well as floor joists, it will lock those edges together for a much better long term job.

Bud
 
  #12  
Old 11-26-13, 07:12 AM
Member
Thread Starter
Join Date: Nov 2013
Posts: 6
Two more questions:

1. Since i'm trying to do one room at a time, i have run the new joists up to near the wall. I am planning on not adding blocking on this wall until the joists are continued into the next room. any issues in going that route? (pic below)

2. Ive got one (original) joist that is about 3/16 lower than the nearby joists (new and old). What is the proper way to shim this joist? I'd be doing a significant quantity of planing to ease the grade, and i'd prefer to shim instead if it is acceptable.
 
Attached Images  
  #13  
Old 11-26-13, 07:50 AM
Member
Thread Starter
Join Date: Nov 2013
Posts: 6
one more...

There is a wide doorway to the living room from my kitchen/dining room. is it acceptable to cut the panels to not continue the tongue and groove at that doorway? essentially I'd be butting my advantech up against the next room's advantech w/o the tongue and groove set across the threshold. the joint would be sitting on blocking though.
 
  #14  
Old 11-26-13, 01:08 PM
Member
Join Date: Mar 2013
Location: USA
Posts: 457
IMHO, the 23/32' panel is OK to cut as long as it is on solid wood blocking due to its (single floor) 24oc rating, per code you are under; 2304.7(3) and (4), footnote "d"; Chapter 23 - Wood

Post 12, 1. That is fine, add it later, but add it. 2. Shims require a non-compressible material (not cedar shims or plywood), plastic decking, plastic trim, metal, etc. joist requires 1-1/2" of full bearing. Be sure to cut off (most of) the joist waste past the bearing beams, rule-of-thumb= no more than the thickness of joist past- 5-1/2", be sure to get (code-required) 3" lap at bearing; Chapter 23 - Wood Otherwise, you could get a teeter-totter effect when heavy weight (single foot-fall) is concentrated on joist mid-span to pop tiles at the 20" overhang past beam end. Be sure to solid blocking at all supports to prevent rotation as per link, not hurricane H-2.5's which are for wind/seismic up-lift, not rotation.

Post 10- no sisters required- they may span more than you have, second chart down- 6-9', depends on the grade; Chapter 23 - Wood No 12"oc required. The 6" to siding is water splash, etc. per code against wood rot; Chapter 3 - Building Planning

Post 8; No need for pt joists or pesticide treatment unless visible signs of fungi (when you cleaned them) or less than 18" ground clearance to joists (per code). The decking under S.G.door appears good at the end grain cut, is it rotten as you probe with screwdriver...if not, leave it be and flat blocks are also required there (anywhere you don't use the T&G edge). Again, IMHO.

Gary
 
  #15  
Old 11-28-13, 08:24 AM
Member
Thread Starter
Join Date: Nov 2013
Posts: 6
Finished the kitchen's subfloor just in time to cook up turkey!
300 SF done ... 1300 SF to go


some things i thought might be useful for others starting this kind of thing:
-an oscillating tool with the scraper blade seemed to work best at removing the old glue
-used a dremel to cut off nails that the heads rusted off on and hammered them deeper in with a finishing nailset (so i could pass over with a planer safely)
-its easier to plane and flatten the old joists before adding the new ones... after i added new ones it got messy of who was too high
-toe kick saw was easier to control if in the first pass i wasnt worried about a flush cut, just removing the old wood. after figuring this i stayed a half inch or so off the wall and it went much faster
-harbor freight toe kicks cant handle more than a few nail strikes before they croak... check that perimeter very well
 
Attached Images  

Last edited by sdiguana; 11-28-13 at 08:28 AM. Reason: added picture
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