Question
I put in a 16/20 brickpaver patio this past summer and it came out real nice.However the syracuse winter may have taken a toll on it.After e recent thaw I noticed my nice new patio was heaving in the middle below the covered patiotable.Is this cuz the weight of snow on the rest of patio(had over 130 in. so far)?.Is this typical? I know my brick entry sometimes heaves a little during the winter but not like this.  PLEEZ tell me I won't have to redo entire patio, but if i do ,how can prevent this from happening again??   thanx in advance; will

Answer
Hello,

Sounds like frost heave (when water freezes under the surface of the paving and then expands,causing the pavement to heave up). Your patio may have poor drainage.  This can be caused by not using the right drainage material under the patio or laying the paving over an expansive soil like clay without drainage material.  The weight of the snow has nothing to do with this.  It would take many tons of pressure to effect the brick.

The brick should be layed on a 4 inch layer of concrete sand.  This is a relatively coarse sand that allows water to more easily run through it.  Masonry sand is often used for this purpose,but it is much too fine and will cause drainage problems.  Under the sand,a  course of gravel should be installed.

The grade is also important.  The patio must be sufficiently pitched to allow water to run off.  In addition,making the surface as resistant to water penetration as possible is important.  Using masonry sand to fill the gaps in the bricks will give more resistance to water penetration as the fine grain of this sand will not allow water to easily pass.

The fact that this heaving has happened after only one season indicates that there is a problem.  After many years of heave/thaw (freezing and then heating in the summer) the paving materials become weakened and slowly heave up little by little,regardless of the underlying drainage material,which often becomes clogged with finer silty particles.

In your case it sounds like an impervious paving surface would serve you better.  I would suggest you consider installing the bricks over a reinforced concrete slab with mortar joints for the bricks and then use a sealant over the bricks.   With this design,most of the water will simply drain off the surface and not get under the brick.  The reinforced concrete slab will resist frost heave to a high degree.  You could reinforce the slab with rebar,wire or fiber.  

I cannot tell you if you will have to reinstall the patio.  Perhaps the heave is just in the spot you mentioned.  But if you do have to reinstall the patio use good underlying drainage material or use the concrete slab design.  If you go with the concrete slab,I would also recommend using gravel drainage under that.  Good luck.  Write back if you have further questions.

Mark  Harshman
http://www.mahdrafting.com
Email: [email protected]

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