Fatrap ... Shed building questions

[Paul P]

Hey Fatrap,



I recall you have a wealth of experience in shed building. Before I called it quits on my shed building for the winter, I had screwed down 3/4 tongue and grove plywood for the flooring. I covered it with a tarp for the winter. I just uncovered it to resume the project and some water did collect on the flooring. This caused some of the plywood to buckle up primarily on one of the outside edges where a screw even popped. In some spots there is a slight bow between floor joists. Should I try to flatten this out some way by loading the buckled edges with more screws or do I need to replace some sheets potentially?



I was also considering coating the floor with some type of paint (epoxy?) to seal up the floor as a one time step. Any recommendations on this?



Thanks!



Paul

 

[fatrap]

Paul

Once tongue and grove or any wood is warped it's almost impossible to get straight again. One headache after another. You can try to screw it down with additional screws but I would just replace it. It will never again lay flata. This is why alot of structures are made with Oxboard. Ox is made up of wood chips glued and pressed together to form a sheet. Since the chips are small the grain expanding cause little distortion. Plus the glue acts to keep moisture out.

Painting will protect the wood from absorbing moisture. A good wood primer then a top coat. Don't forget the ends. This end grain will absorb paint like a sponge just like it will abosrb water.

I hate using enamel or oil based paint but it sure outlast latext. It's also much more durable IMO. Another way to seal wood is a 50/50 mix of polyurethene and mineral spirits or thinner. This runny mix will soak into places thicker stuff won't go. You can paint ontop of it or put a coat or two more of regular poly on it. Sealing dirty wood with poly seems to work better too if you can't keep the wood clean.

The number one item in keeping the floor from warping is a dry roof. It won't rot or warp if it doesn't get wet in the first place.

I use ox or particle board when I'm helping someone replace or build a wooden deck in their boats. Plywood will delaminate and crumble on the edges. It's cheaper too.



Fatrap

 

[Michael Snow]

WHOA there fatrap. Particle board for a boat? Let me make sure I have MY definitions right.



Particle board is "pressboard", pretty much glue and sawdust. Water turns it into mush quickly.



Ox, as you call it, sounds like what I believe to be OSB (oriented strand board I think). It's a bunch of shavings and chips glued together.



Paul, one thing Fatrap didn't say explicitly is that the plywood in question will never be the same size that it was, which is why it's buckling in the first place. It's distorted and no matter how much you try to beat/nail/screw it into submission, it's larger than it originally was (and hence as Fatrap said, will never lay flat again).

 

[fatrap]

Mike have used it with great success. Properly treated OSB it will not warp or split. However you cannot cover great expanses of area without underlying support. Ribs aluminum framing some underlying structure for support so it won't sag. My brother's Lund has an eight year old floor. No problems. He got his flooring/siding from houses he was helping frame. That's where I got the idea.

Getting back to the issue of sheds. The floors of many premade sheds are Ox(not particle)board.

Would I rebuild premimum aluminum bassboat with it? Probably not. Do a jon boat or an old resort Lund semi V?Yeah slop a buch of poly on it and carpet it,.

Fatrap

 

[Paul P]

Thanks Fatrap ... I figured you would say that. This is depressing me. I thought I would save time this spring by putting the flooring before winter. Now I have to rip it out and put new stuff down. It sounds like you are suggesting Ox board for the floor rather than plywood for the shed. I'll see if I can find some. Do you think tongue and groove is necessary?



Thanks



Paul

 

[Paul P]

I used exterior grade screws for the flooring. I'm assuming these are preferable to nails. True?

 

[Dennis Ciccaglione]

Paul,

You are correct in using screws unless you have access to a nail gun.



Depending on how bad the floor is buckled is what you need to use to determine the course of action. This is for a shed after all. If it is just the edge of the ply & you need / want to replace it; think about just cutting out that section instead of the whole sheet. If your joists are 16o.c. & you are using 3/4in ply then you only really need to cut over to the first joist (cut at center of joist). When you replace the ply with the new piece put down some sub-floor adhesive like PL400 (comes in a caulk tube) then screw the new piece in.



For sheds I do recommend both the top bottom & all edges of the ply be coated. I had done this for years when I was a builder. One of the easiest things to use & cheap is standard oil base deck paint.



If you have an questions just ask glad to help if I can.

Dennis

 

[fatrap]

Paul

Screws are always better than nailing but nail are ok. I watched a commerical operation put sheds together. The use a nail gun. Yes the use OSB or Oxboard. I believe it was around 3/4" but may have been 7/8". If you have some stringers in the floor or joist 16" on center that'd make your base floor really strong.

I have nothing against plywood and if you want a super primo floor 3/4" exterior is the way to go. Did you know that difference between marine plywood and exterior is that Marine plywood doesn't have air voids and exterior grade has. Learned that at the Plywood speciality store FYI.

fatrap

 

[Paul P]

Thanks guys this is great information. I'm learning so I'm working on understanding that I will make mistakes and will have to redo certain thing. I won't get back to the shed for a couple of weeks but I will let you guys know how it comes out.



Two more details questions:



1. - Is tongue and groove necessary?

2. - Should I leave 1/8 inch between the sheets?



Thanks



Paul

 

[fatrap]

That I can't anwser for sure. The eight inch I assume would be for expansion from moisture. It wouldn't be a bad idea.

fatrap

 

[Dennis Ciccaglione]

Paul,

Tongue & Groove is not necessary for a shed but it doesn't hurt either. As I stated in an earlier post use sub-floor adhesive like PL400 (comes in a caulk tube) then screw down the ply, & you will fine.

If you need or have decided to purchase new Ply for the shed floor make sure it is exterior grade, min. 5ply 3/4in (again tongue & groove not necessary); if you decide to use OSB / OX makes sure it is a min of 3/4in and your joists are no more than 16"o.c. You will see more flex in the floor with OSB then with Ply.



Either way I like to seal all sides of the flooring & then sub-floor adhesive on the joists before installing.



Plywood / OSB for the decking should be butted as tight as you can get it. Absolutely no gaps should be left between the sheets.



Dennis

 

[Larry Harp]

I would think that some gap, perhaps a 1/4" around the outside edge of the plywood decking to allow for expansion would be wise. In a house you would cover that gap with 1/4 round but in a shed it wouldn't be necessary.



Harpo

 

[Dennis Ciccaglione]

Nope.. Really no gap, Ply should be as tight as possible when abutting pieces & it should be cut flush with the end box on all sides. When you raise your walls they should sit flush with the ply & end box also. As you install your exterior sheathing have it run all the way down the wall covering the flooring ply & the end box.

This is the case with a shed, a house or just about anything else built in this fashion.



Sheds see more moisture than a house deck will ever see because the underside is almost always exposed to the elements; that is why I recommend sealing all sides. Exterior grade ply does not expand very much because of the contrasting grains; it delaminates which is a different problem. Seal it, sub-floor adhesive, abut it tight, stagger the seams, screw it, cut it flush on the end box, & call it done....



Git-R-Done!!!



You won't have to fool with it ever again.



Dennis

 

[Paul P]

Thanks for all the info everyone! I'm just back from a 9 day family vacation so I will begin planning my shed new shed work. My current plan is to frame the walls on the ground before redoing the floor. I'm hoping to get the shed buttoned up as quickly as possible once the floor is redone. Last winter, n my haste to make progress, I made some mistakes in the flooring installation ... it got wet, buckled and it was not exterior grade but t&g underlayment. As I mentioned earlier, I will most likely redo this. Once I frame the walls, I'm sure I will have more detailed questions on the flooring. Right now my plan is to go with an exterior grade 3/4 and seal it first before installation. I'm going to then screw it in place with adhesive on the joists.



Thanks again!



Paul

 

[Dennis Ciccaglione]

Hey Paul,



Sounds like you are on the right track...

Little food for thought: Think about redoing the flooring first, it will make the laying out of the walls much easier. Not to mention the new deck will provide a nice flat surface for you to build the walls on top of. Build the wall on the deck & then just raise them right into place, if you want to be away ahead of the game you can square them up & sheath most of the wall before you raise it.



If you are interested in doing it this way let me know I'll walk you through it...



Dennis

 

[Paul P]

Hi Dennis



The only reason I was considering framing the walls before I rebuilt the floor was to minimize the amount of time that the new floor could get wet. I would prefer to do the floor first but I won't be able to finish it in one weekend so it may be exposed. I did cover the original floor with tarp but must have collected condensation over the winter. If I redo the floor, paint it, and cover with a tarp until building resumes, should I be concerned about it getting damp or buckling?



You recommended exterior plywood. I'm assuming that would mean ACX. Is this the right type and from the comments above it sounds like tongue and groove really isn't necessary? The current bowed floor is underlayment, 3/4 inch t & g. I'm assuming this is not exterior grade so probably a bad choice to start with ... what do you think?



Thanks



Paul

 

[Dennis Ciccaglione]

Paul,



If you are only talking a couple of weeks to a month you will be fine with the floor exposed; house decks are sometimes exposed for months. It is most likely not that your current choice of flooring would not have worked fine and I'm sure what caused the problem was not it getting wet or absorbing moisture, but the fact that it froze before it dried out which caused it to delaminate. Regardless of what anyone says all ply will do this even exterior grade. This is why I recommend it to be sealed on all sides. I recommend this always on a shed because the bottom of the ply is almost always exposed to exterior moisture & the actual deck will stand up better to abuse. (as above I usually use exterior oil base deck paint; I like med. or light gray, makes the shed brighter & easier to find small parts when you drop them)

You can standard CDX if you want or even T&G, what makes ply exterior grade is the glue used in the laminating process, other than that pick the finish & type you like.





Hope this clears some stuff up. Let me know if you have any other questions...

Dennis