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dbeamer 07-22-2012 01:15 PM

Attaching retainer wall forms to foundation
I want to build a 3' high 1' in ground, total height 4', 6"wide retainer wall. Up hill side will be level with top of wall using drain rock & cloth. It will only be 4' long and one end will be perpendicular to house foundation. I want the end close to the foundation, about a 1/2". I want to use 1/2" joint expansion filler between the wall end and foundation. I want minimum exposure of water seepage thru this area. What is the best/easiest way to do this? Anchoring forms against foundation? How many anchors and type? I thought about leave- in-place metal form that can be fastened to forms but don't know where to buy or can i make one? Any help is appreciated.

TRUEPRO 07-22-2012 03:56 PM

You retainer wall will fail like this. You need a base footer for the wall to sit on preferably 8" wide. Not sure why you need to secure the forms to the original foundation? If you must, pre drill and use tapcons.

dbeamer 07-22-2012 07:23 PM

I did not mention it will be on a 12" wide base & rebar for a single pour. How do I get the end of the retainer wall close to the foundation and provide a support for the poured concrete?

TRUEPRO 07-22-2012 08:15 PM

Obviously your not having a professional build these forms? Not the hardest task but kinda hard to explain to a novice (no offense).

Ummm....where to start... Ask mort or joecaption or canarywood they could prob explain a little better lol sorry

concretemasonry 07-22-2012 08:40 PM

Where are you located?

In many areas it is recommended to NOT directly tie a exposed retaining wall to a house foundation, because they see different temperatures and moisture, so they move differently.

I have seen retaining walls heaved by frost enough to cause costly repairs to a home, including some underpinning.


TRUEPRO 07-22-2012 08:46 PM

Ya and concretemasonry too their the ones to ask**

dbeamer 07-22-2012 09:09 PM

I do not want to attach the finished wall to the foundation. I was asking about attaching the forms to the foundation with a 1/2" expansion joint between foundation and the retaining wall. An easier way while keeping the space between the wall and foundation small is the goal.

dbeamer 07-22-2012 09:23 PM

I'm located in Santa Cruz, CA and I'm sure that don't allow connecting to the foundation.

pls8xx 07-23-2012 07:45 AM

Your proposed wall footer is not wide enough, suggest 24". And the footer should be separated from the house footer as well as the wall separated from the foundation. Will the new wall footer be above the elevation of the house footer? Use several vertical rebar ties from the new footer into the wall.

I assume since there is so little concrete in this project that you will be mixing on site. Do the footer and wall in two separate pours.

Do not attempt to hold the forms together by attaching to the house foundation. This is not a good way to counter the force the wet concrete will have against the forms. Butt the forms against the house foundation with the expansion material between the forms stuck to the house foundation. The wet concrete will push the expansion material hard against the foundation wall for a tight fit.

Do you need help in making the forms?

dbeamer 07-23-2012 01:44 PM

Thanks for the great info. The wall footer will be above the house footer. I planned on using vertical rebar from the footer to the wall. I will be mixing on the site. I wanted to do a mono pour to avoid putting in a water stop. Since I plan to use drain pipe, rock and cloth behind the wall it is not a big issue.
Is the main reason for doing the footer separate is to provide stability to hold the forms butt up against the house foundation, assuming all forms and bracing are adequate? I've seen the force of cement bulge, twist and break forms to often, so I wanted to avoid any weak spots with this project. I envision the cement pushing the forms away from the house foundation. Will a few 2 x 4's at a 45 degree angle, along with a separate footer, bracing the 4' long wall end toward the house foundation be enough to hold it against the house?


pls8xx 07-23-2012 03:11 PM

Try to hang the forms in the air to do it in one pour and it will come out a mess. A flat footer gives you something to hold the forms in place and adjust for a perfectly vertical wall face.

External bracing can be used to hold the forms against shifting away from the foundation. If it were me, I would probably extend the footer a bit beyond where the wall will end and put in a J bolt. Do a light broom finish to the footer around the J bolt to give the added wood a good "bite". After the forms are in place a doubled piece of 2x8 can be drilled for the J bolt as a bottom cleat for the forms. An additional brace would be needed at the top of the forms.

Build the wall a few inches back from the front edge of the footer so that if you later want to add a brick or stone veneer you have a base to start from.

Do not use external bracing for the face panels! The front and back form panels need through-the-wall ties; snap ties or 3/8 allthread with bolts.

Holding the wall forms vertical can be easily done by running chain from near the form top to a secure ground connection a few feet away. Do a chain both from front and back panels at both ends of the wall. Leave slack in the chains when installed, then gather up the slack with a turnbuckle. The chains will force the form down tight against the footer and by loosening one turnbuckle and tightening the other you can adjust the form position to a perfect level.

If you are confused on anything I can maybe do a graphic or photo.

The pros may not do it this way but it works for this homeowner.

dbeamer 07-24-2012 02:43 PM

Thanks for the very good recommendations. I never would of got the idea of using chain and turnbuckles to hold the form down and vertical. It sounds perfect and I have plenty of chain and turnbuckles. The j bolt idea with details was also needed.

I was planning on use x type flat snap-ties but can't find anyone local that stocks them. The simpson tie's I believe only work with 2x's. They have the heavy duty round ones but I didn't want to deal with the extra lumber and snap-tie wedges for such a small job. I could always order the x type on line, but not sure what size plywood they use. You mentioned 3/8 allthread with bolts. Is that a brand name or just threaded rod with a bolt on one end. Could you tell me how to use the allthread so I could remove them for a finished look. I know the round type of snap-ties have coils imbedded so the rods can be turned out, but this would still require all the extra wood and special clamps. All of your advice has helped a lot. Thanks again.

pls8xx 07-24-2012 03:47 PM

To pour a lot of low garden walls I made my forms 48" wide by 32" high. They are re-useable bolt together forms from things you can get at the hardware store. The graphic below will give you a general idea. If you decide to go this way I'll give some more detail.

pls8xx 07-24-2012 03:57 PM

Some wall. The plastic spacers were later tapped out for re-use.

Mort 07-24-2012 08:20 PM

Pouring it monolithically would save some time, but building the forms for that is kinda complicated. You'd probably be okay with something as short as you're thinking (taller walls and it'd blow out, and your kids will learn a bunch of exciting new words), but don't make it harder than it has to be.

I don't remember seeing it, but make sure you don't just stab some vertical rebar in the footing for the wall and call it good. It has to be bent and tied in to the rebar in the footing, or it won't stay in there.

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