Hello. I am pouring a 18" stamped border around a patio. Most of it is covered and protected from the rain. The width of it is mostly 10' with a section that extends approximately 10X15', My question is the border completely forms around the middle patio section; therefore, sort "enclosing" this middle section which I believe will not allow for expansion. 1) Should I put expansion joint material along the inside of this border before I pour the middle section. 2) Do I still use the 1/4" drop per foot guideline. I understand about sawing or troweling control joints when the concrete is wet, but I am not sure with this one.

I am trying to understand your question. Some aspects do not seem clear. My impression is you want to add 18" of concrete around your existing patio. When pouring concrete against itself you have a possibility of water freezing in the gaps and cracks of the old patio and the new 18" stamped concrete. Depending on the condition of the existing edge of your patio may help you determine what amount of separation you need to apply to ensure water does not penetrate between the existing patio and the new 18" concrete you plan to place. I would suggest that when you place concrete against existing concrete you install dowels, 'typically 12"-16" in length through the middle of the existing patio concrete edge. These dowels will extend 6-8" into the area of the new concrete patio to maintain a level transition from the existing to the new. I would also suggest that the 18" new concrete have a thickened edge of no less than 4" I would like to send you a sketch if I can.

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Originally Posted by jsnbrd

I am trying to understand your question. Some aspects do not seem clear. My impression is you want to add an additional 18" of concrete around your existing patio. When pouring concrete against itself you have a possibility of water freezing in the gaps and cracks of the old patio and the new 18" stamped concrete. Depending on the condition of the existing edge of your patio may help you determine what amount of separation you need to apply to ensure water does not penetrate between the existing patio and the new 18" concrete you plan to place. I would suggest that when you place concrete against existing concrete you install dowels, 'typically 12"-16" in length through the middle of the existing patio concrete edge. These dowels will extend 6-8" into the area of the new concrete patio to maintain a level transition from the existing to the new. I would also suggest that the 18" new concrete have a thickened edge of no less than 4" I would like to send you a sketch if I can.

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Thanks for the response. To clarify, It is a new patio with a stamped 18" border pattern. The middle section will be poured a few weeks later. All is all it is approx. 1000' sq ft of concrete patio. I guess my question was do I need 1/4-1/2" expansion joints between the border and when I pour the middle section later. As well, A few sections will butt against the house slab. I was going to put expansion material against those areas. Unless, that is, you have maybe other ideas? Doweling? Do you mean drilling into the slab and epoxying rebar (doweling) to tie it all together?

Well, for expansion joint to perform as designed there has to be a an exposure to more extreme conditions. Such conditions would be; most likely to be frozen in winter or heavy point load weight. Using expansion joint will create a much larger separation between finishable surface. Concrete retracts as it cures so there is movement. In that large amount of force for movement 1,000 SF patio. I would at least use a 1/4" expansion if you are looking to reduce stress related cracks. You should check into the vapor barrier material prior to placing concrete checkout some Wiremesh for the middle section. Tie the mesh to the dowels. You should have a nice structural patio.
The 1/4" drop per foot guideline is to direct the flow of water when it travels off the surface e of a concrete patio. Quantity of water in question would determine the size of your expansion. If positive water flow is obstructed or if water will be prone to sit in areas where concrete abuts to existing concrete or Brick. You want to be able to maintain those areas over the life of the patio. To be safe againts water accumulation I would apply a slope to the concrete suitable to ensure positive flow off the surface. The expansion can help create a flow line at buildings edge, but because you are in between two areas where elevation has become a factor you may be unable to utilize the 1/4 drop per foot guideline.