House Foundation Formwork 3

[rory704]

Looking at putting in my own foundation for a new house. The basement I'm planning is to have 10' high walls. Any suggestions for the best/easiest way at forming this? I'm currently considering using 10' lengths of plywood with 2x lumber for bracing with tie-backs.

 

[concretemasonry]

You better have the 10' high wall engineered. That is not the same thing as a 8' wall that you can do by the IRC "cook-book" tables.

You definitely need a registered engineer based on you description.

 

[msquared48]

Setting the forms properly with the proper amount of ties, to include the reinforcing can be a tricky matter, especially for a 10 foot wall. Unless you know what you are doing and can withstand the $$$ loss and delays of a blowout, get a good foundation contractor.

Mike McCann
McCann Engineering

 

[bimr]

Why don't you rent the forms? It would be expensive to buy the wood for formwork and then throw the wood away when you are done.

Not sure why you want to do this type of work. It is not usually that expensive and it is hard labor as well. You would be better off working on the high value items.

All the money in the house is in the finishing work, not the rough building. For example, a 2 X 4 - 8' long costs about $2. Trim boards cost $1-2/ foot. A kitchen faucet or a whirlpool faucet goes for $200-400.

 

[Maury]

I agree with bimr. Form rental is better than making up your own from new plywood. And hiring a contractor is better yet. Do the footings your self if you want but have a contractor do the walls. It's not a job for amateurs. The risk is hig (both financal and safety) and the cost saving isn't enough to make it worthwhile.

 

[rory704]

I understand the concerns. Yes, I'm trying to save some money and that was my reasons for looking at doing it myself, along with doing the finishing work. Another reason for doing it myself, from being on job sites and overseeing the construction of formwork/placing concrete, I learned you need to watch everything your contractor does to make sure it is done right (reinforcement placement, wall penetration locations, vibrate, etc). So, why take time off of work and pay to watch someone else do the work when I can do the work since I'm already taking off. With doing it myself I would get a few people to help out.

I did start reconsidering the 10' concrete wall and may go with an 8' concrete wall with a 'knee wall' on top to give the basement more headroom.

I tried doing some searches for form rentals in my area (MA) but couldn't find anything so far. I do work with some structural engineers and they would make sure my formwork detail is fully braced if I go with building them myself out of plywood.

I have received some prices from contractors to do the work and was getting low to mid 20's for a 55x40 house, this is not a square house though just the overall dimensions. I figure I can do it for about 10k less.

 

[GrumpyG]

Most home builders use aluminum forms. They are lightweight and can be easliy carried. You may be able to get an engineered shop drawing from the form rental company. Ask the person that sells the reinforcing steel for a reference for form rental. They may also rent forms as well.
Other equipment needed would be vibrators, layout equipment, and a strong back.

 

[civilperson]

The addition of a "kneewall" is the same engineering problem as the wall built to full height. Build the wall to desired full height at a measured vertical pace, i.e. two feet vertical in one and half hours. Use one foot level lifts and vibrate through the current lift into the previous lift. The slow pace will lessen the hydraulic pressure so the bottom of the forms do NOT BLOW OUT. Steel forms are best and economical to rent. Time spent cleaning and oiling is necessary.

 

[fldengnr]

Do not try this yourself!!! Take this from someone who does formwork daily. Watching a contractor is not the same as doing the work for a contractor. All the aside wall ties,whalers,stiff backs and all the other components are set at specific locations and secured to prevent the concrete from blowing out the form and make the structure stable. Plus it takes one of our 5 man form crews about 4 days to form and pour a wall approx 16ft high and 30ft wide and that is using plywood forms.

 

[rory704]

Thanks for the advice. With some additional searching I found some form rental places.

 

[BRGENG]

In our area the existing wall heights (up to 8ft) in the City building codes will not work if using values from IBC or IRC. Remember that the pressure on the wall is a factor of the height squared, so a do foot wall has more then 50 percent more pressure on it then an 8 ft wall. Most homes are built with considering the wall is to be pinned at the base and pinned at the top by the floor framing. However they never consider the lateral loads from the soil and if the floor can take it, usally not. Or they will backfill the wall before the floor framing is installed and complain about the walls leaning in. They wonder why the 2 ft wide footing would not work. Then comes the cracking because they used #4 bars at 24 inch o.c. which is really inadequate and they added a lot of water so they could obtain a nice 10” slump. Then to save money they don’t install a perimeter drain or don’t install it correctly so you get a nice hydrostatic pressure building up behind the wall. Which the original wall that was undersigned to began with really can’t handle. Now they call an Engineer to figure out what went wrong, but by know the engineering fees are higher and the construction repairs costs will shock you.

Save yourself the headache, call an engineer to began with.

And homeowners wonder why their basements leak?

 

[DRC1]

Try A. H. Harris. Tey are on the'net and probably in your area. They rent Steel "Symon" panels. Barker Steel also rents a similar form and sells rebar. They will give you lay out drawings plus technical support. To start the forms on top of the footings, you wil put down a 2x "shoe" to attach the forms. Be sure this is done properly. The forms go together pretty easily, and can easily handle 10 feet. Be sure every thing is tight and well braced. Pour slow, don't overvibrate. Hopefully you can find a couple of friends who have done this before, but if you don't rush, you should do fine. Good Luck!

 

[Speedycrete]

Have you considered ICF's? (Insulated Concrete Forms)

They are very Do It Yourself friendly. Some are better than others for a tall wall. I was an owner/operator of a concrete pump, and I pumped into about 10 different brands of forms. You will have to pay for quality. Nudura forms are some of the best. Superforms are good too. Most all of them will supply you with a video to show you how it's done. Some of the larger distributors will also have the bracing/integrated scaffold to rent to you. There is a great deal of information available on the 'net.

Good luck

 

[onyeuko]

If you are an engineer, you should be able to carry out this job confortably. A 10' high wall is about 3m high wall which is about the normal or standard wall height(unless if I did not understand the whole thing-right!)The problem is only with the the loading that will be coming from the surcharge earth and impounded water, particularly when it rains. In this case, you have to provide good drainage in the form of weep-holes on the walls that are submerged, collect the water from the weep-hole and discharge. Remember to place a good drainage medium between the wall and the surcharge(retained earth).Alternatively, between the walls and the surcharge earth, place sand or gravel or a mixture of both(as drainage medium) and under this arrengement, place drain pipes (nornal porcelain or cenent pipes that are perforated on their upper portion. Make sure that the water draining from the drain medium is directed to the top of the drain pipe which you should in turn connect to a discharge pipe. Then make sure that the drain can safely be discharge(by gravity or by pumping- you should recognize that this is not a child's play). You can analyse the structure using free dowmloadable excel program for retaining walls which will give you the requisite reinforcement, the spacing etc.
Constuction of the wall should be done in bits as not to have bustings and pressure build-up normally associated with long tall walls casted at a go. Casts in lifts of 1m(about 3ft) on spans of 3m (about 10ft) shoud be ok!. Rent the forms. It is better you carry out the job yourself as to have a feel of it(as long as you are an engineer!). You already have enough professional advices to see you through.
Good luck
Teddy

 

[civilperson]

BRENG,
What pressure are you referring to? Soil pressure is linear and proportional to height as is water pressure. Concrete hydraulic form pressure can be lessened by waiting for the early set of the cement, thus the slow vertical pace recommended, but it is still proportional to height.

 

[onyeuko]

The soil and water pressure are the ones to be dealt with by the weep-hole or media drainage and structutal reinforcement of the walls. These needed to be designed for. Sharewares on the sites can do this confortably. The other pressure from concrete hydraulic are those to be taken care of by the staged construction as to allow them to dissipate before casting the next lift, thus control of cracks. As to busting which is as a result of the weight of overlying wet concrete, this is also taken care of by the staged construction as the lifts that have hardened do not impose weight on the formwork.
I do not know if I got your question as such if I answered your question well. If not, write again and please be clearer
Teddy

 

[BRGENG]

onyeuko, I would not recommend that you use weep holes for a basement wall. That all but guarantee’s a wet basement. Exterior walls that is great, but for basement walls you need an exterior drain.

 

[fldengnr]

I think what all of you are forgeting is that you are giving all of this information on suppliers to rent and erect wall forms so that he can form and pour his basement. What everyone seems to have forgoten is that he has no physical experience in erecting concrete formwork. Gentleman this is not something that you do with the documents that come with a symons panel and a trip to home depot. Once again I will say " CALL A PROFESIONAL CONTRACTOR "

Tim

 

[rory704]

True, I never actually did the physical labor in erecting forwork, however, I supervised and approved the placing of concrete for foundations walls and piers (along with drilled shafts,footings and pads) on many job sites, without a blowout. Since I was looking at physically doing it myself I wanted to get as much info as I can, thus my posting. But I might still consider a foundation contractor, though I have worked with many different contractors (foundation, framer, electrical, roofer, surveyor, geotech, etc) and it can be a gamble who you will get.

For the hydraulic pressure I have little concerns. My soils are sand and gravel. When doing the test holes/perc tests for the septic we went down 10' in 3 different location on my land and no ground water. The BOH said not to bother actually doing the perc since any water would drain straight through the soil and would be very hard to perform. Just for caution I will still install a drain pipe on the inside of the footing with a sump pump as I have nowhere to drain to on my land.

 

[onyeuko]

Brgeng, I recommended a weep hole as an alternative to the sand media drain/perforated pipe approach. I did not give it as a definite line of action, of course. But I want to point out that that alternative(the weep hole is very feasible as we have incorporated them into some walls over here in Italy). There is nothing particular about it. make the weep holes, connect them to collector pipes and drain by gravity or pumping. The water does not go anywhere near the inside of the basement. The drain pipes can be incorporated into the wall or floor system if you like. But with the recent information that the author has given, it seem that it will not be necessary to go all that way long as the soil has good natural drainage. But he has to be cautious. As to fldengnr, remember that the author is not only preoccupied with the the form work thing which I beleive is the least preoccupant. He is interested in every thing that could make the project a success, as such we do not have to restrict ourselves to the formwork issue. Well it has all been an exciting topic to discuss.
Good luck to all of us in our endeavours.
Teddy