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Old 02-27-2011, 11:30 PM
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TomG TomG is offline
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Join Date: Dec 2010
Location: Londonderry, NH
Posts: 675
Originally Posted by SVA_Concrete View Post
i would be curious what the engineer on that job thinks.

i wonder if it was omitted from the construction drawings or the contractor omitted it.

even if it is just a 3 foot area, that 3 foot is the most crucial when directly adjacent to a structure. where is all the water going from that impervious roof??? if there are gutters on the home i would suspect a large portion is being directed to that "little 3 foot flower bed"

how many years has this wall been in place?
SVA, The wall has been up for 5 years. This wall was designed by an independent engineer and he did not include any drainage pipe. The plans were also stamped by the town engineer, so two different engineers approved of no drainage pipe. Also there are gutters on the whole house and none of the downspouts direct water to the 3ft flower bed. As you can see from the pictures of the back of the house it is quite large so there is plenty of space away from the wall for the gutters to outlet.

I will say that drain pipe behind SRW’s is pretty much pointless. Is it a best practice to use it? Yes, without a doubt. Does NCMA recommend you to use it, yes. But have you ever gone to a wall that you have installed and checked if water is coming out of the drain pipe? If you have, I can guarantee that no water was coming out of it and never will IF the wall was properly installed. Meaning good compacted stone base, proper number of rows buried below ground, sufficient excavation of soil behind the wall replaced with clean drainage stone, proper compaction of stone and any soil that was put back/better soil that was brought in, proper geo-grid installation (if needed), a swale 3ft-4ft behind the top of the wall to help keep water away, etc…

SRW’s are non monolithic, unlike say a poured concrete wall, so there are spaces between the blocks where water can exit from behind the wall. One thing that really cracks me up when I see it being installed is using 4” black perforated flex pipe as the drain pipe behind the wall. IT’S PERFERATED ALL THE WAY AROUND, if any water gets into the pipe it’s just going to go out the bottom of the pipe through the holes. Especially if it is completely surrounded with stone.

Now if you have an engineered plan and it specs drain pipe, you better be damn sure were putting it in or else were screwed if the wall fails. Likewise, if the wall were discussing fails because of no drain pipe we have no liability because we followed the engineer’s plans (assuming we did everything else correctly). I can honestly say that we have never had a wall fail in the 15 years or so that we have been doing SRW’s. The walls at my parent’s house are 13 years old; it’s a double tier wall, each wall about 4ft high with steps going up the middle. It has no drainage pipe and has held up extremely well. (I have a picture of it but I can’t seem to locate it, I will do my best to find it tomorrow and post it.)

Now I’m not saying that every wall we do does not have drain pipe. I think of drain pipe as more of a “feel good” part of the construction. You put it in so you can feel good about the job, or make the customer feel good. And there is nothing wrong with that. Personally I think the drain pipe looks horrible when you exit it through the front of the wall no matter how good of a job you do cutting a hole for it through the block. Also I am only speaking from experience in the New England area of the US, different soil type’s effect walls in different ways. Anyways sorry for the short novel, it’s just my opinion and I am curious as to what people think.

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