Boontucky-girl
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| 10/31/2008 10:50 AM |
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I have done my basement with ICF, and a question I have is can the basement be backfilled before the first floor deck is in? The walls were poured two weeks ago, and the slab is going to be poured on Monday, so the concrete in the wall will have cured about 3 weeks before we can backfill. Would I need some sort of bracing?
Thanks
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thagreen
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| 10/31/2008 11:09 AM |
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No question about it. The floor has to be put in before the backfill is done. This gives stability to your wall to sustain the lateral pressure. Seconly this helps eliminates the risks of being rained on when finishig the floor and helps heating the space if needed. So multiple attributes come with the floor installation.
Cheers |
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wes
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| 10/31/2008 7:58 PM |
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Boontucky,
the answer to your question is absolutely yes. Put your first floor joists and sheathing in place before backfilling.
If your walls were installed properly and with three weeks cure time, the odds are that you would have no problems with backfilling. HOWEVER, if you do have a problem, it could be minor-walls bowed in slightly, or major-basement walls laying on your new basement slab. Whatever the degree of the problem, it will not be easy or inexpensive to repair. Its far simpler to wait until the first floor is in place to add the extra protection. |
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Wes Shelby
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Murray KY
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ICFconstruction
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| 11/03/2008 9:35 PM |
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The safe bet is to wait until the floor system is in, but realistically more often than not, at least what I see, back-filling is done prior to the floor system being installed.
A more important question than bracing is how is the back-filling going to be done. Again more often than not, back-fill is loosely pushed next to the basement and the excavator is gone. Safe for the excavator, but the worse thing that can be done. That loose soil, once saturated is a colunm of liquid exerting great pressure on the foundation (hydrostatic pressure), if not now, in the spring. And for years to come the fill will settle next to the basement.
The best method is done when the fill is compacted every foot or so as back-filling takes place very little pressure is exerted on the wall; they will be not hydrostatic pressure and you won't have settlement issues. |
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Brad Kvanbek - ICFconstruction.net |
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wes
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| 11/04/2008 6:53 AM |
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ICF,
What type of fill are you recommending?
Most clean wash rock doesn't require compacting. And that should be used as fill, at least for the first 1-2 feet horizontally from the walls and up to within 6-8 inches of finished grade.
Also, my understanding is that any type of soil that can be compacted, will eventually become saturated with water and develop hydrostatic forces that could affect the walls.
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Wes Shelby
Design Systems Group
Murray KY
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ICFconstruction
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| 11/06/2008 9:55 AM |
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We have mostly clay, but compaction should be done to all back-fill. Porous back-fill, sand, gravel and so on, hydrostatic pressure is rarely a problem but the loose gravel will act fluid if not compacted and will cause more pressure on the walls than when compacted, especially if equipment is on top of the non-compacted gravel.
Clay when compacted is almost always damp but solid, and sheds water. If it is not compacted the water is shed by the virgin clay and the loose stuff next to wall absorbs it, resulting in a fluid colunm against the wall. Another way to reduce pressure is, when in clay soil back-fill and compact gravel next to the walls. |
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Brad Kvanbek - ICFconstruction.net |
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Boontucky-girl
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| 11/06/2008 2:12 PM |
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My dilema is that the framer is delayed on his current job, so he can't come and set the deck on our house until two to three weeks from now (if weather doesn't delay anymore!), and here in Iowa that will be winter and the ground will be frozen then. I don't think we can backfill with frozen dirt! Can we? This is why I'd like to know how to back-fill without the deck in place. Not to mention that the framer wants to have the back-fill in place before he comes to set the deck. He said it makes his job much easier.
Also, our excavating contractor doesn't use any rock as fill. He simply uses the dirt that was dug out of the basement site. Should we be using rock? I have clay and sand for soil that was dug from the basement.
Thanks for your help.
We have #5 grade 60 bars 18" o.c. in the walls, just because I wanted to be conservative since around here 24" to 36" o.c. grade 40 is typical if they use vertical steel at all. Would that help at all with back-filling without a deck? |
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thagreen
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| 11/06/2008 3:11 PM |
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Well, if you do backfill, which you shouldn't, give yourself some lateral support and hope for the best.
However I strongly advise against this idea. The time you'll gain is nothing compared to how much you have to lose!
Good Luck!
The right choice isn't always the best choice! |
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ICFconstruction
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| 11/06/2008 7:05 PM |
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| You do not want to back-fill with frozen fill, it may create excessive pressure when it thaws with all those voids. Compact as you back-fill and you only are creating pressure on the amount you are compacting. For example if you compact in 12" lifts you are only exerting pressure on 12" of wall. Similar to why we fill our ICFs in lifts to lessen the pressure. |
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Brad Kvanbek - ICFconstruction.net |
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Paul Stevens
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| 11/07/2008 4:25 PM |
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Are you braces still attached if so backfill away! Depending on the height of you basement and how long the walls are without a corner you shouldn't have a problem backfilling 4-5 feet, If you have a section with lots of jogs, T intersections or a cold room you should be able to backfill to the top without any issues.
Paul Stevens |
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Boontucky-girl
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| 11/10/2008 9:43 AM |
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Thanks Thagreen. I'm thinking we will wait for the deck, but that will be probably in the first week of December that he would set the deck. If we backfill in the middle of december, what do I need to do? The ground is starting to freeze, so if it does freeze, do I pretty much have to wait until spring?
ICF, we're thinking that we might go with using rock as fill around the house. Can we use rock in December? Any special type of rock to use? Around here we can get crushed limestone. Someone said to us to use pea gravel, but not sure if that's wise or not. The excavators around here say that it's no problem backfilling whenever and just using the soil around the house, but for some reason I don't trust that since it's not their house and they want to make sure the income is flowing. (Which is why I pester you guys here since you have no vested interest in the property, and what I get is honest opinions!) Another thing is we just found out that the excavator uses a dozer to backfill, and I though that was not the way to backfill a foundation. Or is using a dozer all right?
Paul, braces are long gone. We have the slab in place, and we will wait until the deck is on. Now I'm just trying to figure out how to backfill in the middle of December. What if it starts snowing?
Thanks, |
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thagreen
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| 11/10/2008 2:53 PM |
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If your backfilling with crushed stone you can do it whenever but you'll still need to prevent frost from hitting your footing in the meantime! Clear 3/4 stone would be the best for drainage/backfill, pea stone isn't such a good idea plus is more expensive and doesn't drain well.
Cheers!!
Ps. Frozen fill is a bad idea on yours excavators part. |
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lkazanov2
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| 11/10/2008 5:00 PM |
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Aside from protecting the foam from UV, what is the rush to backfill? Bracing considerations aside I think that a firm floor deck is the best method of stabilizing the top of the wall. In addition, I think a poured slab would also provide additional insurance to stabilize the bottom of the wall. Not having seen your construction photos is the backfill necessary to aid the framers?
I agree that frozen dirt is probably not the best fill. In terms of gravel to aid the foundation drainage what is the consensus for 1-2" clean stone or #57 (same stone as you would lay under the basement slab)? I think the dimples membrane would protect the foam well with this type of backfill.
Leonard
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Chris Johnson
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| 11/10/2008 5:46 PM |
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| Without the floor system installed and providing you don't have really long straight walls (say 40' with no corners or bump outs) backfill 1/2 way up without issue. I did this all the time and in one section on a short wall I would back fill 100% as a ramp or pathway to get on the walls and install the floor. Nothing worse than setting up temp planks that are never made safe and having to dispose of them after the job is done. |
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Chris Johnson - Pro ICF
Napa, CA
Come for the wine, Stay for the ICF work |
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Boontucky-girl
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| 11/12/2008 11:00 AM |
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Thagreen, what should I do to protect the footings? We've got the footings covered with about 6" of pea gravel and landscape fabric right now. We miscalculated how much blueboard we needed to use under the slab, so I have a bunch of that. Could I use it and place it on top of the pea gravel for now? Or do I need to do something more?
Ikazanov2: The rush to backfill is that we wanted to cover the footings with dirt to protect from freezing. We will wait for the deck, and the slab is already poured.
Chris. Our longest wall is 32 ft, and since it is a walkout basement, the grade line starts at 8 ft high on one side and it slopes to about 2 ft high on the other end. The other side the longest wall is 21 ft, with grade at about 6 ft, with two window wells, the other walls on that side are 16ft and 17ft and the ground slopes on them as well. We might just have to do halfway up. In front of the walkout wall there is enough room to drive a truck in there, so we believe the framer can use that instead of trying to use planks.
Thanks for the help. |
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Paul Stevens
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| 11/13/2008 6:37 AM |
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4 feet of backfill is all you will need to protect from frost, you should be fine, but if I were I would make a decision pretty soon, winter is just around the corner!
Paul Stevens |
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gregj
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| 11/13/2008 2:34 PM |
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| Is the backfill really going to protect from frost? Afterall there is no backfill on the inside and it certainly isn't heated if there is no deck. I suppose it will help since the cold can only attack from one side. |
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thagreen
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| 11/13/2008 2:57 PM |
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Paul is wright but I'd go with 6 instead of 4 just to make sure(two feet ain't a whole lot mmore work) ,unless you pack it. You will have to make sure the interior stays above freezing point to prevent frost. Put your deck on! From what I've read it'll take half a big day. Then it'll be much easier and sure for all else. Don't forget the snow cause it won't forget yo.! It's coming fast!
Cheers ! |
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Boontucky-girl
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| 11/14/2008 1:57 PM |
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Paul, Greg and Thagreen thanks for the info.
Greg, I worry about that as well. There is 2" of insulation under the slab so I was hoping that would help retain some of the ground heat for a little bit on that side. If the framer can finish with setting the roof on his other project, he could be at our house next Thursday to set the deck. So crossing fingers.
We've got the dimple board installed, but with all the rain we've been unable to get the final caulking and flashing needed to seal the top of the waterproofing. We're lucky that Sunday is supposed to be high of 45º, so we'll be caulking then. I think we might have to have a heat gun go before the caulk gun to get the surface temperature up at least long enough for bonding (and hope we don't burn the dimple board!)
If the framer is delayed, we decided that we might have to have to start backfilling ourselves in foot lifts and compacting each lift as was suggested before. Thank God no snow in the next 10 day forecast (but you know how reliable that info is!) The highs are between 30 and 35, and overnight low's are in the low 20's for the next week and half.
So do you think
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Boontucky-girl
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| 11/18/2008 12:15 PM |
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| I guess my last post didn't post completely. I wanted to ask that in the event that we can't get backfill in time before the ground freezes, what do I do? |
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