When to backfill?

[Jawgarage]

Today we finish the block foundation and temps will be in the 40's - 50's for a couple of days before dipping into the low 30's this weekend and perhaps colder. I will have my foundation inspection tomorrow or Thursday.

So assuming all passes, I have a few questions:

1. When can I backfill and start prepping for the slab work after the inspection ?

2. The ground here is all sand sand sand. I assume that is fine to use as the backfill up to the height of where the gravel will start under the slab.

3. How long to wait for the slab to be poured?

4. You will see in the pictures that one 10' long portion of the block wall is 2 1/2 courses above grade due to slope of ground. Anything special needed to be done on the outside of this wall before the inside backfilling and slab work begins to make sure it does not get damaged? When finished the slab height inside will be almost 1 course above the outside ground line in that area. Should we simply berm that portion higher on the outside of the wall for support?

Thanks everyone.

Jeff

 

[readhead]

Probably the first move will be to remove all the dirt inside the foundation. If the cells are not grouted solid you need to back fill equally on each side. If you want to back fill above the floor you may want to water proof the section that will be above the slab. I'm not sure what your inspection involves but you should be able to prep and pour as soon as possible. Does the inspector want to see the slab prep?

 

[matt_i]

If it were me I'd chip out the top webs of the block and add in a perimeter rebar, then core-fill, adding some more vertical rebars for reinforcement. Put in your J-bolts for the bottom plate into the wet 'crete.

In my opinion, the biggest stress is going to be any powered equipment moving sand/gravel fill materials around, pressure from compacting it, and then the weight of the wet concrete when it gets used as a "form". After that its pretty much just the building's vertical loads. The inside shouldn't really get wet and present additional loading as it could with say a retaining wall.

In any case I'd keep any exterior fill or sod from being equal to or lower than the plane of the bottom of the concrete floor, to avoid water intrusion.

 

[bczygan]

Horizontal and vertical wall steel in place?

Insulation?

U/G utilities?

 

[kbs2244]

Back fill to an equal level inside and outside the wall.
That avoids any side load.
On you high side slope the fill at 30 degrees to avoid a washout of your sand.

 

[Jawgarage]

Horizontal and vertical wall steel in place?

Insulation?

U/G utilities?

There is no certicle or horizontal wall steel going in other than the Z Bar between each course.

No Insulation

Power will be run later and penetrate through framed wall.

 

[Jawgarage]

If it were me I'd chip out the top webs of the block and add in a perimeter rebar, then core-fill, adding some more vertical rebars for reinforcement. Put in your J-bolts for the bottom plate into the wet 'crete.

In my opinion, the biggest stress is going to be any powered equipment moving sand/gravel fill materials around, pressure from compacting it, and then the weight of the wet concrete when it gets used as a "form". After that its pretty much just the building's vertical loads. The inside shouldn't really get wet and present additional loading as it could with say a retaining wall.

In any case I'd keep any exterior fill or sod from being equal to or lower than the plane of the bottom of the concrete floor, to avoid water intrusion.

No need to rip out top as only the core holes with anshir bolts are filled. The rest were not filled and its not typical tondo so here. I likenthe idea on that slop side though and may do that with some verticle rebar when pouring the slab.

 

[brownbagg]

you need to block fill the cavity of the block as soon as possible then you can backfill once they get hard

any block under slab get 100% filled as per code

 

[Chris705]

International building code does not require to fill cores that fall below the slab. NJ falls under this building code.

 

[Jawgarage]

Thanks. So am I reading this correctly that the Code does not require cores be filled or for vertical rebar to be used in a detached garage with poured slab and cement block wall on top of poured footings placed at proper depths past frost line?

Sounds like it may be beneficial to use some rebar on vertical wall where it is above grade by 2 1/2 courses but not required. Is this correct?

 

[brownbagg]

International building code does not require to fill cores that fall below the slab. NJ falls under this building code.

yes it does.

 

[JbTech]

As an aside, I would suggest putting stone in front of and behind the entry wall.

It's something we would always do to eliminate compaction / cracking after final grading.
Might help with the sand, which will compact until it sinks.

 

[Chris705]

Yes would be best to get vertical reinforcement at corners and roughly 4' oc. Aligning this vertical bar with dowels coming out of footing and 1/2" anchor bolts at top of wall will help hold your garage down in high winds. Grouting these cores solid (not all of them) locks it all in place. Being tied into footing helps prevent overturning when a wall acts like a cantilever from loads place laterally on it(such as compacted soils). So we all preach about how one needs to compact backfill to properly support the slab. Here is what I would do if this situation were my own... your 2.5 courses above grade can be fully filled and compacted minus 20" measured horizontally from inside top of wall. Angle the fill down to outside grade height from this 20" perimeter. Roughly at a 45* down... then fill in this 20" perimeter area with stone fill with only minimal compaction.... then pour slab.

 

[Jawgarage]

Thanks guys. Had inspection and all good except not all Cap Block core holes were filled and need to be before framing. Good news is that this allows time to still core fill the corners and such.

Question.....Its 50 today but Ive only got about 36 hours before it dips to 32 degrees overnight then back into the 40's for another 12 hours or so before we get this arctic blast into the high 20's for two nights. So is it too cold already to core fill today? Do it and use hot water? Material confirmed by Quikrete as best to use that is available is their Top Sand Cement premix.....

 

[Chris705]

Will be good....you want a couple days of above freezing temperatures....dipping to 32 at night for a low won't be a problem... if it dips much more then I'd be more concerned.

 

[Jawgarage]

Thanks Chris705 and everyone else for the helpful advice. Spent a few hours yesterday and filled 14 cores and placed vertical rebar at the same time. Now all short sections on sides of doors, all corners, and 48" OC in the areas that are 2 courses above grade are core filled with rebar. It will also be 48 hours before the below 30 evening temps hit.

Muscles killing me today but real glad I did it!!!!