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Large subfloor in basement


ianC's Avatar
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04-11-06, 07:09 PM   #1  
Large subfloor in basement

Hi
Been reading some posts here but couldn't find exactly what i was looking for, so i thought i'd start a thread to get some input.

I'm finishing my basement, and could really use some general advice on the subfloor. It consists of 2 large rooms, both 26'x40'. After some debate between a 'dri-core panel' type system, 2x4 sleepers, and the lot, I decided to go with a full 2x6 subfloor. I've ordered up the wood (2"'x6"x12') which should arrive Thursay (hopefully). I'm a little at a loss as to how to construct it though.

I've thought about creating 2 "boxes"; i'd create a 12' wide box and frame the inside 16" oc, then bolt the 2 together and top w/ 5/8 t&g ply. Thing is, 2 12' boxes only give me 24', 2 feet short of the width of the room. How do you frame such a large span properly?

Further, should anything go between the concrete and the 2x6's? Perhaps vapor barrier?

If my descriptions are not clear enough, let me know and i'll render you a truly exceptional drawing of my thoughts.

 
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04-12-06, 04:25 AM   #2  
That is one hell of a sub-floor. I am curious to know why you would use 2x6s?

You need to install 6 mil poly under the subfloor to avoid contact between wood and concrete.

Nail in some 2' spacers between the two "boxes" which will give you the 26 feet you need.

 
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04-12-06, 02:48 PM   #3  
My reasoning for 2x6's is partly mine and advice from others. First, I'm planning on putting 2 bathrooms in, and this will alow me to plumb a toilet without breaking the concrete up. The ceilings are quite high, so even at the lowest point it should still be about 7'9" high. Secondly, i've been told that a 2x6 floor will feel much warmer and be easier in the feet than 2x4 sleepers nailed to the concrete.

By spacers, do you mean a 3rd box, or just 2' sections nailed inline with the other 2 boxes?
Sort of like:

__________ __ _________
|________| __ |________|
|________| __ |________|
|________| __ |________|
|________| __ |________|
|________| __ |________|

Where the red sections are "spacers"?

 
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04-12-06, 03:09 PM   #4  
Only reason I know of to use a raised floor would be if there is some serios moisture problems. The drycore system isn't bad but expensive and you can get rolls of the indented spacer and lay OSB plywood on top of it and you have about the same thing without quite as much expense. To raise the entire floor just to accomodate plumbing is not very sound sorry. Assuming you have plumbing already roughed in in the basement (almost all newish houses do) It is much better to just chip the floor up where you need to. Also out of the dozens of basement I have finished not one did I not have to move around the roughed in drains for something so you will probably have to chip up some concrete anyway. Losing 6" of headroom would be unexceptible to me even if there were 10' ceilings. You can rent an electric jackhammer that makes pretty easy work of it.

 
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04-12-06, 04:14 PM   #5  
re moisture - This is actually our first year here and this springthe foundation (cinder block) is leaking at the corners. I wouldn't call it flooding, but puddles did form. I plan to try and tackle that from the outside come summer, so it hopefully will stop for the most part.

re dricore - I gave up on the idea of dricore due to the cost. I have to floor about 2600sqft, and dricore would cost me both arms and legs. I thought about the plastic on a roll stuff with T&G plywood, but the puddles scared me off. (This is to be permanent rented living space).

I had the same reaction to breaking the concrete as you, but others warned me off it. They said it was to much work. I'd at a minimum like to use 2x4 sleepers, as being from Canada that concrete is going to get pretty cold come winter. The ceilings (slab to joists) vary between 11' and 8'4". They are high, but I agree with you on more is better.

I've already bought the 2x6's, but I suppose I could return them. I'd like to hear some more comments on this if possible.

P.S., should I lay any poly over the concrete first?

 
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04-12-06, 04:40 PM   #6  
any timber that comes in contact with concrete is supposed to be pressure treated. Also if you have moisture problems coming from the walls you will definately need to barrier them as well. Drywall soaks up moisture like a sponge and will bleed through fairly quickly even with just a little. Does your basement have a sump pump? If not you need one. Are you saying there is actually standing water in places? If so yikes! You will have to get that basement completely dry before you can build on it. A poly vapor barrier is good but it will not resolve heavy moisture. I can't see your basement but I know I hve warned people in the past about finishing an even slightly leaky basements and it turned to disaster when unheeded. Again I can't tell how bad it is from here but often the case is save a little now to spend a fortune later. Last thing I want to do is destroy confidence in a project but I hate to see expensive mistakes as well. Good Luck!

 
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04-12-06, 05:19 PM   #7  
Thanks, i appreciate the advice.

The water that leaked in during the thaw was a puddle, say about 1'x1', which dried up within a week. A sump pump is in, but i have to level the concrete to direct the water to the pump. I'm hoping to have solved the leaking for the most part by summer's end, but it is a risky decision to go ahead assuming I can stop the leak. So should i seal the poly on the floor to the poly on the walls, sealing the subfloor and walls in with the living space?



I've posted some pictures so you can get a better idea what i'm dealing with. This was taken after the water evaporated. You can still see the dampness in some of the block, and damage from previous leaks.





 
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04-12-06, 05:57 PM   #8  
Yes risky indeed! I can't stress enough how important it is to have that basement completely dry before you even start on the finishing. I had a job recently where the homeowners wanted an existing finishing job removed (old and unprofessional) and replaced. There was 3/4" pine paneling along the exterior walls which water had bled through making green moldy patterns everywhere. Plus the whole basement stank of mildew. It was completely unihabitable. The foundation was granite stones and was barely damp to the touch (after I demoed the paneling). I refused the job until it was water proofed. I didn't do the work but this is how it was done. A trench was dug all along the exterior walls to be finished. Then a plastic channel with holes spaced in it was placed in the trench (not corrugated piping which is often used but a smooth channel to avoid clogging) then a special vinly sheeting was anchored to all exterior walls to be finished with the end going into the trench. Concrete was then poured into the trenches securing the vinly sheeting into the trench allowing any water coming from the walls to be channeled into the trenches which were in turn channeled to the sump pump. The floor was then covered with the raised matting and topped with 3/4" OSB plywood. That may sound a little extreme but the basement is guaranteed waterproof for the life of the structure. It was not cheap I'm afraid at around $8,000. There does appear to be some leakage through your block that would concern me. Not saying all this is absolutely nescessary but I would be real sure before you start building that all leakage is under control especially if you have standing water ever.

 
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04-13-06, 04:44 AM   #9  
Posted By: ianC re dricore - I gave up on the idea of dricore due to the cost. I have to floor about 2600sqft, and dricore would cost me both arms and legs. I thought about the plastic on a roll stuff with T&G plywood, but the puddles scared me off. (This is to be permanent rented living space).

I had the same reaction to breaking the concrete as you, but others warned me off it. They said it was to much work. I'd at a minimum like to use 2x4 sleepers, as being from Canada that concrete is going to get pretty cold come winter. The ceilings (slab to joists) vary between 11' and 8'4". They are high, but I agree with you on more is better.

I've already bought the 2x6's, but I suppose I could return them. I'd like to hear some more comments on this if possible.

P.S., should I lay any poly over the concrete first?

I am located in Ottawa. I think you got some bad advice on the 2x6s. It is overkill and a waste of money.

I did not have the headroom to build a subfloor in my basement, so I had no choice but to put laminate flooring on the concrete floor. My walls are fully insulated and have proper cold air returns and supplies. The space is very comfortable. 2x4 sleepers will be more than enough.

 
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04-13-06, 03:28 PM   #10  
O.k., I think i'm going to return some of that lumber. Taking the advice you guys gave me, i think i have a better idea of what I should do. I've got a few questions (o.k., a few more ) and then I think i'll be ready to put the rubber to the road. Thanks again guys for the good advice...it's quite hard to come by nowadays.

-use 4-mil poly under the floor and behind the walls. Should the poly on the floor be between the slab and the sleepers, or the sleepers and the plywood? Between the cinder block and the wall studs, or the studs and the drywall? Should the poly on the floor be tuck taped to the poly on the walls for a seal?

-what about the corrugated plastic mat? Would this be a better substitute for the poly between the concrete and the sleepers?

I'll also invest some extra time outside digging up the foundation and trying to seal up those leaks.

 
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04-13-06, 04:05 PM   #11  
Large subfloor in basement

If you have been in the home for a year or less and do not know the long term history of water/moisture control, you are taking a very big gamble. If you have a problem, whatever you put in will come out and have to be scrapped/replaced.

When you mention having to direct the water to the pump, indicates there is a problem. If it evapoarates in a week now that it is exposed, it probably will never evaporate when it is built over. It almost sounds like you do not even have drain tile and proper exterior drainage.

I would take the time to find out what you REALLY have before wasting a lot of time and money on a major project.

Dick

 
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04-13-06, 04:31 PM   #12  
I think I identified the cause of the three leaks. I realize without being here, it's hard to give advice, but i'll put up some pictures to help with my explainations. I've also noticed cracks in the mortar in the areas of dampness and leaking. There are three areas of concern.

The first is a makeshift retaining wall against the foundation in one spot (this wall is inline with the leak shown above in picture 3646 of the waterheater). I'm hoping that this in conjunction with the cracks is causing the moisture.




The second is the the driveway actually slopes towards the house, which I believe is causing the leak in picture 3634 of the water tank.
Kind of difficult to see in this picture...


The last is i think just a gutter pointing straight down into the corner of the house, pictured in picture 3662.

Looks like this:


Do you think I should try and remedy these problems and wait another year till spring, or is there another way to do this properly?

Again feedback is appreciated.

 
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04-13-06, 07:50 PM   #13  
Large subfloor in basement

I would say you have a lot of exterior possible drainage problems to work on before investing a lot of time and money in your basement.

Long extensions (beyond the excavation limits of the basement) are necessary. Also you shold have a positive slope (away) from the house.

Do you happen to live in Ontario or the NE part of the U.S.? You have some interesting split/pitch faced concrete masonry units along the side.

Nice looking garage doors from what I could see!

Dick

 
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04-14-06, 08:06 AM   #14  
Posted By: Concretemasonry Long extensions (beyond the excavation limits of the basement) are necessary.
Sorry for the lack of understanding, but what do you mean by long extensions beyond the excavation limits of the basement? Are you talking about checking for/installing a weeping system?

Posted By: Concretemasonry Do you happen to live in Ontario or the NE part of the U.S.? You have some interesting split/pitch faced concrete masonry units along the side.
Thats pretty impressive...I do live in Ontario (Alliston), how could you tell?

Posted By: Concretemasonry Nice looking garage doors from what I could see!
I've actually replaced these since the picture

 
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04-18-06, 04:35 AM   #15  
In picture 3692, it appears that the face of the bricks above the basement window are de-facing. This is usually a sign that there is excessive moisture behind the brick.

Concretemasonry should be able to confirm this.

 
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04-18-06, 06:19 AM   #16  
Large subfloor in basement

ianC -

1. Yes, you should carry the roof water out beyond the relatively impervious soil that is in the excavated area around the basement. If not, you could be collecting all that water around your basement. If you are in an area of very permeable soil, it is not as critical.

Good construction practice is to install either and exterior drain tile system around the perimeter of your foundation and direct it to a sump for collection and pumping out. I had to put in an interior system in a home I bought on a hill.

You should also apply a good waterproofer on the interior walls for cheap insurance. I used Thoroseal, but there are others.

2. The split architectural block may have been made by Rob Shouldice at Shouldice Concrete Products or licensed by that company. No matter where you are, you do not have "cinder block" in the basement walls. They are concrete masonry units (concrete block). Cinders were only used in localized areas of the U.S. around railroad yards and some power plants over 50 years ago.

3. I still like the look of the garage doors. My townhouse association would frown on them since the are the wrong color.

Dick

 
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04-18-06, 10:47 AM   #17  
Posted By: ianC -use 4-mil poly under the floor and behind the walls. Should the poly on the floor be between the slab and the sleepers, or the sleepers and the plywood? Between the cinder block and the wall studs, or the studs and the drywall? Should the poly on the floor be tuck taped to the poly on the walls for a seal?
You live in Ontario, so the minimum should be 6mil poly.

Lay the poly on top of the concrete and then lay down the sleepers. You want to avoid contact between wood and concrete (concrete carries moisture which will rot wood).

 
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04-19-06, 03:52 PM   #18  
Thanks guys...

Very informative and helpful posts. I promise to put this new knowledge to good use. I've got a couple more questions, but they are unrelated and i'll post them in there respective catagories.

Once again, thanks!

 
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04-22-06, 09:30 AM   #19  
Hi guys

Sorry for reviving this old topic, but in regards to the plastic channel Concretemasonary was talking about.....is this the Waterguard channel? I've just had a guy come in to give me an estimate, and he uses this waterguard channel with thermaldry products. Does anybody know if channels of this kind are available to purchase? I think the Waterguard channels are dealer/installer only.

 
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