Compaction Tests

[Lanelle]

We will be building a patio behind a new house. The swimming pool has been put in and now the builder is backfilling around it. The grade had to be raised at least 2 feet for the sub base to be nearly the correct elevation. Let's just say that we are not impressed with the fill dirt or grading at this point. Fortunately we wrote in exclusionary clauses about compaction of the sub base and put in a requirement for a compaction test to be performed. Now the question:

How deep into the sub-base should the test be done? Should it be tested all the way down to the native grade?

[Rex Mann]

Lanelle,

We have always had it checked as it was installed in lifts. Max at 12 inches.

Pool areas are never compacted well. You may want to water settle it.

Let us know what the geo-tech eng. says.

Peace,

Rex

[Paul]

Do you want soil borings or a compaction test? Most compaction testing is done with a nuclear density test. This involves driving a rod about 2' deep into the soil then taking a reading. A soil boring would show what the soils are made up of and it's ability to hold the required load by soil type. In other words do the soils have any problems (peat, layered black dirt under clay, ect) Both might be needed. You should check with a testing service in your area and explain to them what you want and ask them to write what corrective action should be taken. One problem is how new is the home's foundation? Can it take the stress that might be recommended by the testing service? What type of load are you going to put on the surface?

[Lanelle]

I want something stable to build the pool deck on so I'm not going back and relaying the pavers 3 extra times. And I'm pretty sure that the soil didn't go in lifts. You should see the large stones that were also pushed into this area. Even pushed them up against the foundation. I asked how I was supposed to plant in that mess.

[Rex Mann]

May be a job to walk away from?

Peace,

Rex

[Stonehenge]

Ug. You just know there are going to be big air pockets in there that won't settle out for a few years. I'm interested to hear about how this compaction test goes.

[PSUscaper]

I don't know why you really need a compaction test.

I can tell you the result right now...........not enough.

If this is a brand new house along with a brand new pool..........of course it isn't going to be compacted.

I don't know a builder anywhere that would be sure to use proper compactible fill dirt and then, install it in lifts and compact.

Unless the builder was told to do this, it isn't going to happen.

The only solution is to let this place settle out.......at least 6 months, but perhaps a year. As we all know, it could take at least 3 years before the thing is settled.

My pool guy is starting to offer 3/4 stone and compaction of it around there new pools as a option for people who want there patio right away.

I recently was told of a job, where the pool company put a pool in, and then, the people decided they didn't want to wait for it to settle. The excavator came in, dug it all out, and then re-installed gravel and used a roller around it.

I don't know the scope of the work your doing, but it would have to be one serious patio install to warrant compaction tests.

Just state in the contract that, due to inadequate time for the new ground to settle, you are voiding any warranty pertaining to sinking.

steve

[Paul]

My main worry was the condition of the concrete, not the compaction. We all know how to do the compaction. If is too green the concrete would crack and there would be problems down the line with the home owner and builder. Taking out 12" of fill and running a sheep's foot roller on it would add only slightly to the total cost, around here your talking $2500 up charge.