Time to wait before foundation wall is strong enough to move house on

[mccheynebeeman]

Hi there,

It seems to me like finding the answer to the question above is a black art on its own, but I'll throw it out there in hopes that someone can give me a more definite answer.

The basement I plan on building will be formed using IFC block (3" Styrofoam/side 6" gap for concrete) at a height of 10ft. The dimensions are 46' X 26' roughly and the house to be moved on is a bungalow. I understand that concrete needs approx 22-26 days to fully cure, however my dad (civil engineer) suggested that my house could be moved on merely 3 days after the pour (this does not include backfilling). Is 3 days enough time?

Another question I have is that I have been assured that the 6" of concrete within the IFC is up to code for a 10ft high foundation wall, however all my findings seem state that 8" - 10" thick walls are required for that height. The basement will only be backfilled 6ft.

Thank you for your time,

Frazer RM Ross

 

[cvg]

suggest that you get a structural engineer to review this or ask the contractor to provide structural calculations. have you gotten a permit? I would think that this would be required for your permit.

If designed correctly for the loading, 3 days might be possible - but this is highly dependant upon the concrete mix design including any admixtures proposed to be used for your foundation as well as temperature during the 3 day cure. For typical concrete, 3-day strength might be about 50% of the full 28 day strength. I usually require a week or ask the contractor to provide results from a compressive strength test (break a cylinder) to prove that the concrete has reached it's design strength.

 

[MiketheEngineer]

I would expect a 10'' to 12'' concrete wall with rebar - all depending on soil and drainage conditions. I would strongly recommended an engineered foundation by a local structural engineer.

Many framers will get on a foundation after a day or two - but those loads are minimal and they are trying to get the floor on so they begin back filling.

I would wait at least a week or get tests like cvg recommended

 

[COEngineeer]

First of all, why is it 10 ft high? Basement? Then Ill be worried about 46' span. I am pretty sure youll need a counterfort or buttress to break the span. You need a structural engineer or youll have a curved wall.

 

[mccheynebeeman]

I found this document in regards to this type of concrete form system

http://irc.nrc-cnrc.gc.ca/ccmc/registry/03/13101_e.pdf

From what I can gather from page 5, it looks like the 6" basement walls are structurally acceptable for 3.07 meter heights, given that I place enough reinforcement (although, I don't know what 15M @ 406 means, (size of rebar at X distances?)).

Yes, the MD granted me a building permit in which the application specified the ICF block I would use.

As for 10ft tall walls? The extra cost is minimal to what I consider to be beneficial of having a high wall.

Cheers,
Frazer

 

[TDAA]

Check with materials engineers in the area (geotech). Some may have a concrete maturity meter that can help determine the curing point of the concrete. Our firm has done this for the Extreme Makeover Home Edition show so they knew when to start building up.

Also, you could have a lot of cylinders made, and start breaking them early. You would have to know what strength you need to at least support the dead load. Using a high early strength mix, or a stronger mix would help reduce the time.

 

[cvg]

Per the document you reference - 7 days minimum is required. Plus must be poured in two lifts which will add one more day minimum.

"The concrete must be cured a minimum of seven days before backfilling. The top of the
foundation wall must be supported by the first floor prior to backfilling.

For the wall heights indicated in tables 1a, 1b, 2a and 2b, the pouring of concrete must be done at a rate of 1.2 m/h in consecutive lifts; each lift is limited to a maximum height of 1.3 m."

 

[mccheynebeeman]

7 days it is then. I'm pretty sure it can all be poured at the same time, granted that time is given to allow for the concrete in the first lift to loose its elasticity (as per my talk with the concrete company doing the pour).

 

[civilperson]

Roughly #5 rebar every 16 inches is equivalent to 15mm at 406 mm. The high early strength mix with a few extra field cured cylinders broken at 48 72 and 96 hours would show sufficient strength when achieved. Probably 3000 psi or so.