How much slope for concrete patio?

I'm thinking of pouring a new stamped concrete patio. I've had one contractor in to quote. The patio will be 20' from the house at the furthest point, and he said it would need to have a 5" slope over that 20' for proper drainage. Does that amount of slope seem right?

 

That sounds like an absurd amount of slope! 2" of slope would be plenty, IMO. I suppose with 5" of slope he wants to be sure there won't be any puddles for you to complain about later.

 

5" is too much. Something about 2" or 2-1/2" is about all that is needed.

 

1/4" for every foot, with adjustment made in base material for concrete in my resource books. If my hillbilly math works out right, that's about 5" for 20 ' isn't it? Sorry, medears, I don't do math very well.

 

Twelvepole,

1/4" per foot works well in plumbing drains, but it's too much slope for a concrete slab. The customer doesn't want to feel the slope. What's used around here is more like 1/10" or 1/8" per foot of slope.

 

I would go with about 2.5"-3" of slope myself. After all, water will seek it's own level, so even if the slab is fairly flat the water will eventually drain. Keep in mind though that stamped concrete is not flat like regular concrete. It has bumps and dips that will hold water. More so with deep patterns like ashlar cut stone than with shallower patterns. Also, a lot depends on the contractor's skill at screeding (initial flattening of the concrete). If he's good, there will be no puddles. If he's not, there could be some larger dips that hold water regardless of stamping.
With the boom in popularity of stamped concrete, there are a lot of inexperienced contractors out there who are turning out some horrendous work. Before you let the guy do your work, check him out thoroughly! Look at his portfolio, CHECK OUT HIS OTHER JOBS IN PERSON and talk to the homeowners, see how much experience he's got and make sure you're comfortable with it. Make sure that the same crew that stamped a good job is still working for him now. His guys might have left him and he could be down to a couple of inexperienced guys who don't have a prayer of turning out good work. Stamped concrete has a long learning curve so experience REALLY makes a difference. Good luck.

Pecos

 

Thanks for all the feedback. I thought 5" was too much too. He did my next door neighbors stamped patio a few years ago, and he's been in business for 30 years. If I decide to go with him, I'll first discuss the amount of slope.