Latest Discussions : Basement & Foundation


01:00PM | 08/18/04
Member Since: 10/28/02
30 lifetime posts

Posted this in the patio section but got no response so thought I would try here...

I bought a book on pouring slabs but most of the info was geared towards patios. I want to make a 4 ft wide, 11 ft long flagstone/brick border walkway over cement and I wanted to clarify a few things.

1. The book recommends 5 inches of gravel under the slab. The heaviest thing this walkway will see is people+furniture (it leads to front door from sidewalk). Can I reduce this? Only reason I ask is to reduce depth I have to dig. Can I just place gravel and compact/spread it manually or do I have to have a power compactor? They did not go into detail on this in the book.

2. The book also recommends 3" thick slab. I have no problem with this but it is it necessary or can I put 2"?

3. I want to use 1 1/2" thick brick to border the walkway. I'm assuming flagstone + cement for setting the flagstone will not be this thick. Do I have to put a second layer of cement down after the brick border is in to raise the bed so the flagstone ends up level with the brick? I saw in the book where they have a screed with a board attached to the screed to level the cement below the brick border.

4. I calculated just over a yard of concrete at 3" thick. Is this a DIY project? I have seen people buy concrete from the local yard with a little rented hopper/trailer. I had a friend that poured a slab for an addition himself (had the cement delivered) and luckily he found an expert to help him smooth it out before it dried. But I don't have any strict requirements on the surface quality, right?

5. Any idea if this is regulated by the city? I live in San Jose, CA.


Glenn Good

01:15PM | 08/21/04
Member Since: 09/10/03
314 lifetime posts
5” of stone under a sidewalk is not needed. Forget the stone and just be sure the subgrade is solid. Do not reduce the thickness to 2” or you will certainly experience cracking. I would recommend using 3000 psi, fiber reinforced, air entrained concrete @ a 3”-4” slump poured to 3 ½” thick.

Stone is needed more as a subgrade for a large slab not for a walkway.

The 3000 psi will give you the proper strength when cured.

The fiber reinforcement will help strengthen the slab and reduce the chances of cracking.

Air entrained concrete is designed for use out doors where there is a possibility of a freeze thaw cycle that could do damage to non air entrained concrete. If your area never goes below freezing you may not need it.

The slump is a test used to determine the amount of liquid (in this case water) that was used in the mix. The higher the number the more fluid is present in the mix. Concrete above a 4” slump tends to shrink excessively and will cause cracking. Concrete at 3” slump is about the optimum for overall strength for your use.

Less than 3” thick will not allow for any movement in the subgrade and expansion and contraction will also cause cracking much more frequently than concrete of a lesser thickness. 3 ½” is the generally accepted norm for sidewalks.

A 1 yard pour is a very possible do-it-yourself project provided the temperature is not above 90. The higher the temperature the faster the concrete will begin to set up thus reducing the working time.


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