I am planning on building a game room onto my house, I have a 24' x 18' x 4" thick patio slab now (the outer end is a 12foot radius I plan to sqaure up) and plan on expanding it to 24' x 27', I plan to raise the level to be even with my house approx. 4" and pour 18 inch footings around the perimiter, what is the best way to achieve a good bond between the old and new and what is involved.

You will need a hammerdrill and some 3/8 or 1/2 inch steel rerod .You can drill into the face of the existing concrete and install rerod pins about every foot .This will keep the old concrete and the new from shifting.

The more steel rerod you use the stronger the concrete will be. Most important will be the rerod around the perimeter of the new pour installed in the haunched area of your footer.

Hope this helps.

csavage1
I should give you a disagree here but you only have 9 post And I don't want to start you out that way. I see you are good in plumbing but this is concrete. Sorry.
On a side note welcome aboard! I have goofed also and didn't get a reddie when I should have so returning the same courtesy to you and passing it along.

Is not necessary at all to try to bond the new 4" floor to old what so ever. The new floor is plenty thick enough to hold its own. As a matter of fact Use 6 mil plastic on top of the old floor for a vapor barrier to stop moisture wicking to new floor.

Don't know what your Geo is but 18" wide footer to lay block in is a no no if it's a trenched footer. Its not wide enough to get your feet in and lay block. You can use 18" wide footers if you are on open basement type setup and form the footer. The outer end that radius, past that should be 4"crushed stone flush with the top of old floor. Assuming you are framing out with 2x6s lay 10 block in the footer/trench. Last course for plate should be 4"x6"x16" solid CAP flush to outsideod block wall. After you lay that there is 4" inside block lip left over for the new 4" floor to set on for bearing. This is they way We do it in the trades for a A1 job. The 4" lip for bearing also helps overcome any post settling along the edges of the backfilled trench.

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Yes you are right 21 boat .You have truly give the 100% correct answer .

I was thinking of a floating slab and not a poured footer with a block wall.

If they live in the south there may be no footer below grade.
Your answer is the better way to build by far when frost or load bearing is a concern.
I should have thought of that before I give my thought. I didn't read into the question enough for a better answer.

This can be fun to help and I will do better next time.Sorry

21Boat, I live in Texas if that matters no basement and as far as I know we don't use block in our foundation, but I am a pretty good carpenter/handyman but a newbie when it comes to concrete, I have laid a sidewalk and patio put not a foundation, Is the block nessassary, I am building with 2x6 stud walls and was going to make the footers 8" not 18" I value you advise since you sound like you know what your talking about.

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Originally Posted by ;

18 inch footings around the perimiter//////// going to make the footers 8" not 18" I

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joldfield. I've been building these for 30+ years but I need some help here on the two sentences above.

8" means nothing until a width/ depth number is with it.

So explain or pick one above. You seem to be describing two completely footers here.

I do complete foundations/footers/conc pads etc blindfolded and yet I'm not understanding your description.

The foundation I'm referring to is called slab foundation or house on slab/slab house

I'm not sure what your requirements are for frost/freezing

I assumed the 18" was the width of the footer below grade frost/freezing

You are referring to a mono pour at 18" deep and how wide?

Here we call that a frost footer. My Geo is 3 feet below finish grade.

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21boat, sorry for the confusion, my plan was to pour a slab that when finished would be 8" thick except for the outer edge which will be 20" deep and 8" wide so the footer would be 8" wide and 12" below grade. or 20" total.
Does that make since?

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Originally Posted by ;

when finished would be 8" thick except for the outer edge which will be 20" deep and 8" wide so the footer would be 8" wide and 12" below grade. or 20" total.
/////// when finished would be 8" thick except for the outer edge which will be 20" deep and 8" wide so the footer would be 8" wide and 12" below grade. or 20" total./////best way to achieve a good bond between the old and new and what is involved.

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Sure does that's what we call a mono pour. The part of your post mentioned raising the floor up 4" to meet house. So this confused me now because you posted the floor will be 8" thick?! (when finished would be 8" thick except for the outer edge ) The 8" thick, Does that include the old crete added to the new 4" crete

Also the width of wall/footer is 20" deep 8" thick.

Have you ever poured this type of floor/footer at the same time? How about a conc trowel machine for the top?

I can give you tips on forming and slump order for crete etc. Get back to me on my questions. Thanks.


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my exsisting slab is approx. 24' x 18' x 4" and I am expanding to 24'x27' , I will be pouring 4" ontop of the exsisting slab to bring it up to a total of 8" and pour 8" where I need to square up the radius and there is just grass, and yes the footers or edge is going to be 20" deep and 8" wide . I have no idea what a conc trowel machine is, I have only poured 4" slabs with no footer, so any tips will be greatly praised.

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Originally Posted by ;

I have no idea what a conc trowel machine is,

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We might be in trouble here. A concrete trowel machine is what's needed to finish the concrete floor you want to pour.

The grass that left from the radius to the square part needs to be dug out and 4" 2b clean stone filled back in to old crete level. This HAS to be done to keep moisture from ground wicking into crete. Also the 6 mi plastic then goes over old crete and stone.

I need to know at this point weather you are going to sub out the concrete work? If so I can give heads up on the quality control part. Or I can give step by step on how to do it.

Let me know. My thoughts here is you will have approx 12 yards of crete hear. Thats a full 12 yd truck. Here theres only 12 and 10 yard trucks except for the baby ready Mix 3 yd truck

Forming a mono pour takes concrete turnbuckles and concrete "D" stakes. Unless you can rent them sub it out. My rental stores doesn't rent them. Other contractors rents mine.

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I planned on building the forms and doing the prep work myself, than hiring someone to do the acctual pour, there's a co. in houston that charges approx. 73.00 cu. yd. for ready mix. That's not including labor, so I will appreciate any tips, Thanks a lot.

I plan on doing the forms and prep work myself and hiring a sub to do the actual pour, any help and I would be in your debt.

Sorry for the double reply I did'nt see the page 2 button and thought my first reply did'nt go through

Dig trench real accurate to the room edges.

What ever forms you need to use 2x6 or 2x8 etc take some blocks of wood and scabb onto outside of forms. Double those up to get 3" away from forms. Here is where the "D" stakes come in. They are a hollow 3/4"metal stakes that have holes in the top part around the pin to use drywall screws to screw into the forms for height. Do that and leave the form an 1" high or so. From desired finish floor Once you get all the stakes in get a string line/transit and tap the stakes down working a whole side in steps to level top form.
Nail stakes - metal forming accessories - dee Concrete

A trick here. If the stake won't adjust and hits rock as you adjust remove screw, tap stake and twist with your hand. You can catch another hole in Dee stake to reset ( lock in form height) Also there is a DEE stake puller you will may need that to pull the stakes when done

Dee stakes are skinny so when you pound them into the ground close to footer edge, the dirt wall won't fall back into the ditch. The 2by scabbs offset the metal stakes away from ditch edge.

Now that is done you need to use some turnbuckles that go from top of scabs to ground. Make sure top of scabs are at least 2"+ down from top of form. This will allow the concrete trowel machine to miss the stakes when troweling over the form edge a hair. hears how the turn buckle will work on you job. use the angle end and place that on top of the scabs or forms if necessary. Drywall screw that end ( one screw)

Lest 'time the turnbuckles. look at the threading and get equal gaps so they can be adjusted with both threaded ends. Use More DEE stakes to set turnbuckles. Now you can turn the turnbuckle to adjust the form from side to side to get is straight. I would space the turnbuckle every 5" since you are holding back a lot of crete. You may also have to put turnbuckles at the bottom of the form for a kicker when the bottom of the form tries to twist out from crete weight.

Concrete Form Accessories - Essential Extras

If you can pull this off and get the form right and strong hats off to you. Mono pours are not a DYI at all.

Do you know how to square up to house?


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OK, never heard of using turnbuckles before but it does not sound to difficult, there are a couple rental places close by I'll check there when I get back home, and I can square to the house.
If I can't find any turnbuckles is there an alternitive way to do the forms?

The old 2x4 in place of turn buckles. The DEE steaks are the finial straw here, To raise forms with 2x4 steaks is all but impossible because if the ditch edge being so close. If you can't find Dee steaks you need to offset the trench 4 inches towards the inside dimensions in order to get more top bank to pound 2x4 steaks in dirt.

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Thanks for all you help, I'll be starting the job by mid month, after I get home so Ihave some time to plan.