Housing and Community Development

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My question: I have a residential client with a landing for an entryway that is exposed to the weather.  The surface is horizontal masonry random fieldstone on a poured concrete foundation forming the top step.  The edge at the step is brick masonry on end. I'm not sure if there is slab. The joints in the stone are fairly large because of the random shape of the stones. The surface has reasonably good pitch away from the home. 

The problem is that nearly all the stone has heaved up from water penetrating the joints and the freeze thaw cycles it has been exposed to over the years.  I would like to specify the proper mortar and general installation guidance for resetting the stone and re-grouting the joints.  Lastly, if there are any maintenance tips I can give the owner (like not using salt) that would be helpful. 

Thank you! 

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Alexander Gotthelf AIA
Mountain Lakes NJ
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Alexander

Context is important, so a lot more information  may be needed. But random field stone for a walway sounds like the first rpoblem. If you want to stick with stone in the redo, go for sedimantary rock like flagstone, regular or random, a very flat surface is achievable.

In my opinion, it is not possible to fully waterproof horizontal stone surfaces, but better to manage water. So the first choice is to set the flagging (without mortar joints) on 2"-3" stone dust. If the the dust is contained with a filter fabric underneath and timbers or heavy stone edges so it doesn't dissipate into the soil below or on sides, the landing will last a long time. If the owner insists on a slab, use a deep mud set on top of the slab for the stones - 2"-3". But side by side, the dust bed will perform better because it isn't fighting the the frost.         .   




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Allen E Neyman
Rockville, MD

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