My guess is if the other posts are obviously going through the concrete is they are probably set below the frost line in gravel or concrete. That's probably about 4 feet down. If that's the case then simply cutting a hole in the concrete probably wouldn't be enough. 4" of patio concrete probably wouldn't be enough to support a deck, specially if the patio concrete heaves. Its the ground below the concrete that heaves. The concrete just follows it. The felt is probably a separation between the post and the concrete, so they will move independently.
I live in an area that it doesn't freeze, that is never a concern here.
The really knowledgeable folks that usually respond don't seem to be around. Tomorrow more folks ought to be able to help.
Steve
Steve
If the slab falls and rises with the seasons. About a year ago I had to have the slabs leveled to compensate for heaving, my concern would be if existing post are anchored in the earth, the new post set on the slab which might move at a different rate/direction and put stress on the structure?
ltd
On 6/24/2012 12:54 PM, wired wrote:in what way? It only affects the length to have the top at the level you want it to be.
--- In DoIt_Yourself@yahoogroups.com, "L.T. Davies" <davies@...> wrote:
>
> Steve
> The existing posts are set through the cement and surrounded by a felt,
> I don't know how they are set in the ground as they where there when we
> moved in. For simplicity, I like the idea of setting them on the cement
> slab, however if some posts are in the ground and some on top of the
> cement would that cause a problem?
> ltd
>
> On 6/24/2012 12:34 PM, Steve Wilson wrote:
> >
> > I don't think you actually want to put the lumber down to the soil
> > level. What is usually done is a steel base for the timber with an
> > anchor hole at the bottom is placed at the base of the timber. Then a
> > matching hole is drilled in the concrete to place the anchor. That
> > keeps the timber off the ground and away from moisture that will rot it.
> > This is an example of one I found. There are several different designs.
> > http://www.homedepot.com/h_d1/N-5yc1v/R-100374896/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=post+base&storeId=10051
> > Steve
> >
> > On 6/24/2012 8:44 AM, L.T. Davies wrote:
> >>
> >> I want to put two 6"X6" treated lumber posts into an existing cement
> >> patio for an extension of a deck. The cement is about 4" thick. I know I
> >> can drill a hole in the cement, but is there a way to "drill" a square
> >> hole to fit the 6"X6" lumber into the existing cement?
> >> Thanks,
> >> ltd
> >>
> >
> >
> >
> >
> >
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