drainage issue on older brick patio 1

[tomtom11]

I have a 33 year old house with a brick patio mortared on a slab. Over the years it has settled toward the house and I am getting water running toward the foundation. During a heavy downpour it runs fairly rapidly into crawlspace. The water disappears quickly out of crawlspace as soon as the heavy rain abates. I have not yet gotten water into the basement which is just adjacent to the crawlspace. I assume the water runs into perimeter drains around the basement foundation or into the gravel layer under the basement. This surprisingly never makes the sump pump run. Our house sits fairly high. The water just disappears. Foundation walls are poured and not block. My concern is that this continual drainage off the patio toward the house will eventually undermine the foundation and I will get settling and cracks in walls. Also if this water is getting into the foundation drains these could eventually clog up from overuse. I really don't want to tear out the patio, regrade and put in a new patio due to cost. I have had suggestions to tear up brick and put a concrete overlay over the old slab and grade the overlay to slope away from the house. This also would be quite costly, I think would look patched up and I am not sure would prevent future settling. I had a mud-jacker come and he was afraid that he might damage the adjacent foundation. I am thinking that the best solution would be to remove about a 2 foot section of the patio adjacent to the house where the water is draining. It would look the best if this could be a planting bed but it will probably require some sort of drainage There still would be an area of patio about 8 feet wide by about 12 feet long that would be draining toward the newly cut out area. I would dry to regrade the dirt in this bed to provide gravity drainage towards the yard but I am not sure this will work. My question is that if I need to add drainage to this bed should it be surface drains with catch basins or a French drain or both. I don't know whether a French drain can handle the rapid run off during storms or not. I think that I can get a surface drain to run to daylight but I don't think I could get a French drain to daylight and would need a dry well. I read that a French drain is for ground water and not surface water but could the French drain handle this run off? Does a French drain really need to be 18 inches deep or can French drains be only 4 to 6 inches deep to allow me to run to daylight? Is there any problem putting a French drain this close to a foundation? (I have read that most French drains are placed 4 to 6 feet away from the foundation so they don't pull ground water toward the foundation). I considered a channel drain but this could not be set at the level of the brick and would have do be at the level of the slab because to much water is seeping through the aged mortar down to the slab. There are some cracks in the slab already which would probably allow some of the water to escape below the slab and not be handled by any surface drain I install in the newly created bed or any channel drain that I would install at the level of the slab. I have sent picture attachments of the area of the patio that I am considering cutting out. The area of the house adjacent to the cutout is a former screened in porch that was converted to a family room. It is on a slab with poured footers. The area where the water is puddling and running down into the crawl space is back in the corner of the patio adjacent to the stoop. This corner is the junction of the basement and the crawlspace. I will have to recreate a slope from right to left to get water out of this newly cut out area. Thanks for any suggestions. I can not tell when I preview my post whether the pictures really attached to my posting, hopefully they did

 

[tomtom11]

One additional question I had was any suggestions on packing the back corner where the water is running in with Bentonite clay or does this just divert the water to somewhere else?

 

[oldestguy]

What is the detail of the "joint" between the patio bricks (and the slab) where they join the house? I was thinking that raising the slab would tilt everything away from the house, but if siding is right there, the bricks and maybe the edge of the slab would need removal.
I guess you need to review some of my posts on the problems with typical "french drains". You know of course it is nothing but a trench which can't "draw " anything.

Slab raising is simple, done by QUALIFIED mud jackers. If not done carefully, unintended damage can occur in unexpected places.

Watch out with bentonite. That also can be misused and it sure is a mess to correct.

 

[tomtom11]

My first thought on this problem was to try mudjacking. I had a man come out who I thought seemed quite knowledgeable. He had been recommended by a masonry restoration company that has been in business a long time and he has been in business quite awhile. He did not think that he should try to lift the slab. I think he was afraid of damage to the adjacent foundation and he said that since water was draining into the crawl space that his mud jacking material would just follow the path of least resistance and flow into the crawl space through what ever passages the water enters. At least this is my understanding of his rational. Again I thought he seemed pretty competent to me. Regarding the detail of the joint the patio slab with brick on top of it butts up to the footer of the house but is not anchored to it. The slab to the family room (where you see the windows) slightly overhangs the footer. There has always been a slight gap between the edge of brick and its slab and the footer. This was originally mortared but as the patio settled the mortar had to be repeatedly repatched. Originally the brick was up to near the bottom of the family room slab but not up to the siding on the family room side. I assume that as the patio has settled more water is getting back in this space between the patio and the footing and has accelerated the erosion of soil around the foundation and providing a larger passage for surface water to run down into the crawl space. Before the last mortaring job in the corner the gap between the patio brick and the house footer was about 3/4 inch. As I recall I had to put some backing rod and stone in the gap to support the mortar. Maybe it should have been caulked rather than mortared? I also wonder if there might even be a void under the patio slab due to settling of the original back fill and erosion. I won't know what's going on in the corner until it is torn out I don't think. After this I guess it might be reasonable to let a mudjacker reassess whether he could help. The area where the patio abuts the house adjacent to the stoop is a little different. There is no slab but just the poured foundation wall to the basement which joins patio brick and its slab. I will review your posts on French drains . Thanks for any input.

 

[oldestguy]

I have done some sidewalk lifting with a home made "mud jacker". In order to keep from losing the "mud" at the slab edge, I drove into the soil "chunks" of plywood, later removed. Where it will work, I've even gotten by with sheet metal. Traditionally compaction contractors will inject grout (a grout curtain) in a zone near the possible exit area. After it has set up, that barrier allows them to do the "work" of compaction generally deeper.

Give a thought to removing a width of bricks along walls. Then saw the slab, removing a width there, leaving room for some barrier boards or plywood that are driven down as a barrier. Later fill in the opening to the original condition.

By the way, if I picture your situation right, I would seriously doubt that water from the crawl space will undermine the basement foundation.

There likely are many other possible ways to handle the situation, but likely about as costly as replacement. I'd not be looking at French drains or any other band-aid. Often times some unforeseen situation pops up.


Photo of my mud jack made in 1978 for a house I had then. Did injection into 2" diam holes cored. Loaned to an engineer-contractor about 1980. He added the hose and smaller pipe for 1" holes. He used it a lot and had it in his garage, until I asked for it back about 3 years ago. Had to lift front walk and driveway slabs settled, due to "work" by former owner here. Piston consists of an old rubber shoe sole. Valves are golf balls. Inlet (not visible under at the cross) from a bucket of mud, with hole in its side. Crude but has done a lot of jacking. My use original had the angles flat on ground, but now I need to set them on supports. Of course I could fix that, but why?

 

[oldestguy]

OG again. If I were doing this, I'd make that a single cut, but then use metal barriers. I am sort of a junk user, so I'd find an old washer or dryer or two and cut out the sides to be used for the barrier. Thus only one cut needed. In addition, there probably will be leakage there so plenty of rags will be stuffed in any openings.

An interesting facet of slab jacking happened once that I recall. Somehow, the basement slab of a building, next to an excavation for a new building settled. Luckily the wall footing did not settle. The contractor had a concrete pump on site. He cored a hole in the basement slab and ran his hose there. He then pumped a grout, brought in via a ready-mix truck. No seepage along sides was noted, but up came the slab.

Another site required braced sheeting to hold up a small power plant wall foundation and floor, adjacent to about 10 ft. of cut. When pouring an upper concrete barrier between the sheets and the foundation, a regular down-spout piping was put in place before the wet pour. Later that was the conduit through which concrete was pumped to "compact" any loose ground under that building. These were low pressure required jobs. Yours also is.

Many ways to skin a cat, they say.

 

[tomtom11]

I don't think I can mudjack myself and don't think I can tell a professional how to do it when he did not think he should. I guess I could get another opinion. This is a fairly large area to be raised -probably 8 by 12 feet or more and this is after I cut out the 2 by 15 ft area I proposed next to the house. The slab under the brick already has some cracks in it so I don't I don't think the whole slab will raise in one piece and I worry this will crack out more mortar joints and make the whole patio look irregular. It might just make the existing cracks worse. I read that one of the risks of mudjacking is that the slab cracks as it is raised and that this is not a good thing. I still have the question of whether a rather superficial french drain in the 2 foot wide area that i cut out and placed just a few inches under the soil and sloped away from the house can handle the water coming off the patio in a storm

 

[oldestguy]

Sounds like you are thinking of the many aspects properly, except maybe the French Drain.

Since water draining will follow the path of least resistance, yes a drain of sorts may collect it, but that really would be providing an easier way for seepage into soil below that patio surface and into crawl space. Yes, some will run off, providing you have a decent slope to that "stone filled trench". You will not stop some leakage where you don't want it. With a lot of work and care some waterproofing of the soil surrounding that trench will help, but you really have to know your details using bentonite. A real mess can develop if thorough mixing is not done using correct ratios. A paved channel would do much better, but not a total fix. On that possibility, consider the drainage way you see in your local automobile service department, down the center. You wouldn't need full length open grates. Grates are not cheap. Aside from actually constructing the channel, look at pre-cast channels.

https://www.google.com/search?q=pre...s=org.mozilla:en-US:official&client=firefox-a

On mud jacking, yes cracked slabs may show up as uneven support. You don't just hit one area. You use several injection points. A second opinion by a well experienced mud jacker may help.

 

[oldestguy]

Tom:

On the use of a French Drain, take a look at the link here. The photo at the bottom right shows where a French drain failed.

It is interesting that this link does a good job of noting that filtering has to take place, or plugging results. Unfortunately, most uses of French drains do so without thought to filtering and they fail eventually. In your case, not only would a liner under the trench help, but somehow the enclosure material must filter out dirt coming with the water as well as have some feature for removing that dirt from time to time.

The first paragraph of this link clarifies what I am trying to show. It needs some thought and care of installation. Good luck.

https://en.wikipedia.org/wiki/French_drain

 

[mlblack21]

If this were my house, I would remove one row of the basket weave brick pattern along the house and try to find a trench drain to collect the water and daylight away from the house. ACO Trench Drains are good products and easy to install. I'd definately use the trench drain over a french drain in this situation. Good luck!

 

[tomtom11]

Thanks for the input. I guess a trench drain is the same as a channel drain. I had thought that might be a good option but I was not sure how the drain would be installed. All the pictures I see wound show it to be at the level of the brick. In my case I think due to deteriorated mortar a lot of the water travels down through the cracks in the mortar and flows along the top of the slab under the bricks. I could have all this re tuckpointed but that gets expensive. If I put the channel drain at the level of the slab that would catch the water running off the brick and also off the slab but I am not sure how this would look. We also have lots of tree leaves falling to clog up any surface drain grates and we are gone away from home half the year. I think these channel or trench drains are usually imbedded in concrete and I am not sure this is a do it yourself project for me. I need to find someone locally more knowledgeable in drainage. My landscape companies so far have said tear the patio out and regrade and our brick masons say put on a concrete overlay to re create the slope and the drainage person I called never showed up. Who is the type of person to do this work? A landscape company or drainage company? Thanks for your input.

 

[oldestguy]

Getting complicated now. Trench drain seems suitable, but some negative factors.

Getting a decent slope and still match the grate elev. to the bricks. Maybe lay level, but provide well sloped final discharge, as in a buried pipe.

Providing an entry for seepage from on top of the slab. Planned minimum depth notching of the side of the "U" so as to keep support of grate and yet don't lose collected water out from trench.

Seal the edge of slab to trench joint. Local clay packed in there is probably sufficient. I'd use a 10% bentonite mix.

Weather and other factors. Any leaves to remove annually? Weeds growing in there? Any snow melt and frozen drain, now plugged? Who will maintain in 20 years?

Getting a qualified contractor. This guy has to be well experienced with many aspects, has to have a variety of tools, a variety of different type jobs. A single person house builder might do. Probably needs guidance of an engineer (owner).

Now sit back and consider all costs and relative problems. every option has unknowns. Add a few bucks and look at a new slab and re-do the bricks. This time fix the support soil first..