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When it rains my patio collects water in a couple of spots close to the wall of the house. The wall is now presenting external efflorescence and cracks of the external cement coating. (not sure if anything is wrong under that coating other than excessive humidity).

It is clear that I have to fix the draining for this patio but I don't know what is the best way to do it. Here are the options that I am considering:

  • install a frech drain between patio and wall -the problem with this is that I need to discharge that drain somewhere. For that I might need to extend the french drain around another wall
  • re-grade the patio by adding more sand under the areas where the water pools
  • or by removing everything (gravel,sand, pavers) and re-grading the soil that is the base for the above layers

Which of the above would you recommend? Do you have any other ideas ?

Ecnerwal
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MiniMe
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  • I read an entire theory about the way the water travels through concrete upward and not downward. If I uderstand you correctly you are against that theory about capilarity http://www.buildingscience.com/documents/insights/bsi-011-capillarity-small-sacrifices Did I get that wrong? – MiniMe Oct 10 '14 at 20:08
  • Hi Ben. There is ABSOLUTE NO SOURCE for the water above the level where I see the cracks. The downspout is "miles" away at the other end of the wall. The bathroom is 4 meters away and there is absolutely no sign of problems below it. I can't see water traveling 4 meters on horizontal and not a 1 cm below the bathroom. The wall is clean below the bathroom. believe me that efflorescence is due capillarity. BTW do you mind finding two pictures that would illustrate the two situations?
    Probably there is efflorescence inside too but I can't see it due to a finished basement wall     – MiniMe Oct 11 '14 at 11:29
  • if that is water coming from above in high volume I should see it inside the house and it should not stop there, I should see it in the basement as well and that is not the case. Also all the marks stop at the same level which is consistent with capilarity and it all stops like in this picture http://www.buildingscience.com/documents/insights/content/bsi-011-capillarity-small-sacrifices/images/bsi11_figure_06a.jpg I don't see the metal plate shown in this figure though – MiniMe Oct 12 '14 at 02:44

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Best is probably a combination of french drain and pulling it all up and regrading the base. Also the most hassle and expense, but in terms of function, the best option. And you would then have the option of running the drain under the patio, if that helped with discharging it.

The individual pieces of that that you have thought of are somewhere else along the expense and hassle line, as well as the effectiveness line. Obviously pulling up a few pavers and repacking under them is least expensive, but it will help the water to move away - but if the patio as a whole is not sloped to drain well, it won't help much if you are just moving the puddles around. So, if just a few spots are low, it might be all that's needed, but if filling one low spot will simply result in another, regrading the whole thing looks better eventually.

Ecnerwal
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  • The biggest problem that I see is that I don't know what is wrong, is it the soil base, is it the gravel or the sand that need fixing? How do I determine that? You can see my other posts in this forum for pictures. I might need to do an exterior waterproofing later and ...in this case all this work will be in vain – MiniMe Oct 10 '14 at 11:00
  • Depends on how long the water hangs around. I'd assume that if it stays for a long time (after rain stops) the problem extends to the base, since otherwise the water should drain away through the sand & gravel layers. A persistent puddle would appear to mean that the base itself is not shaped to drain water. If the puddle goes away shortly after the rain stops, the water is going somewhere (of course, if somewhere is into your wall, that's not helping) and just leveling the surface might be enough to direct most of the water to drain away from the house (if the patio is shaped to do that.) – Ecnerwal Oct 10 '14 at 14:22
  • The water accumulates during heavy rains and it goes away shortly after that (1h) but you can see that those spots remain humid, you can guess it by the darker joints between the bricks of the patio. They are also darker because dirt collected there more than in some other areas. This weekend I will have a closer look at everything to see if I can fix it in a quicker way. I guess it will not kill me if I try to remove a couple of bricks to see if leveling those areas and filling in with some polimeric sand will actually fix the problem. If not I will have to redo the entire patio – MiniMe Oct 10 '14 at 20:14
  • "Darker joints and some dirt" after an hour hardly seems worth the effort... but de gustibus. – keshlam Nov 09 '14 at 14:03