Well, if it's off the ground on three sides, then I'd not
worry about expansion problems crushing a foundation.
Frankly, I'd prefer a
concrete deck to one of wood or wood substitute. To keep it
looking consistent with the railing, consider banding the
concrete with whatever you use for the railing, such as Trex
or another wood substitute. Also, consider having diamond
sawed joints, such as every 6', instead of troweled in ones.
They look neater, IMHO. I'd also consider using the
fiberglass reinforced concrete and also look into air
Sorry for the misunderstanding. When someone says concrete
and deck in the same sentence, my mind automatically says
that they really mean a patio.
Expansion joints are there to relieve stress from the concrete
shrinking as it cures, not to stop pushing against the house, [quote]
called expansion joints because of what happens when the
I guarantee without enough room for expansion between the house
the slab - a poured wall will give in before a 30 ft slab will.
doubt things expand - have a look at this link.
When concrete cures, the first thing it does, is it shrinks. Without
expansion joints, the concrete will crack from that before anything
else. That was where I was coming from. You are of course correct
that it will expand and contract from temperature too and expansion
joints are there to relieve that potential to crack too.
Now what does any of that have to do with your warning that"
"That much concrete will push against your house, even with expansion
All you have to do is have normal expansion joints, placed about 10 ft
apart, like in any concrete pour. It has nothing to do with the fact
that the OP wants a large patio and that somehow this means that it
can't be done as normal, expansion joints.
If the poured concrete somehow gets below the expansion joint (as I
have seen it
do) it will come to rest against the house foundation.
When both the slab and
the house expand in summer they will push
together. They dont expand together.
They are separate and expand
separately. (just like the pictures in the link)
Unless the foundation wall has been designed strong enough to push the
the foundation wall will crack.
I am no concrete worker - but I do understand
physics and have limited
personal experience with both concrete patios and leaky
rather not get into that.
As I said earlier, I agree a properly
installed expansion joint should
prevent the problem.
The material is typically purchased in pre-cut 3-1/2" wide
strips, since a 4" slab is typically formed with a 3-1/2"
2X4. Screeding the pea gravel is usually done before the
strips are inserted, since the concrete is usually what
holds them in place. My guess would be that about 95% of
the pours have areas where the pea gravel is lower than the
3-1/2" strips either because of sagging in the middle of the
screed board, failure to insert the strips fully or having
them pushed up as the concrete is being poured or floated.
It doesn't take much concrete-to-concrete contact to
transfer the pressure directly to the foundation. All a
good contractor would have to do would be to take his foot
and make sure that there was pea gravel under the strips to
prevent concrete from getting under them.
You are right about it being caused by poor workmanship, but
that's just what happens in real life. The best way is to
use gravel to separate the pours, when it comes to patios.
That sounds like a very nice deck. With all the engineering that will
required - I'm sure thermal expansion will be fully incorporated
in the design.
IMO I think it would be better than a wood deck for a few reasons.
provide a rainproof area below.
No splinters. Low maintenance.
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