Hi,
Im renovating a workshop and have to replace 4 joists. One end will sil just below ground level, in eatch essentially and I am worried that it will rot. I have located treated joists 3x8x144 inches and am planning on cementing them in.
Is there any other way? Something else I should be doing? Will this be enough or is there a damp proof product, plastic sheeting / foam / something else?
Any advice would be really appreciated!
Mike
I did some work in a very old house and recall that a portion of the back corner was below grade. This resulted in rotting of the sil and the ends of the joists. One solution was to change the entire grade of the back yard - very expensive. In this case the contractor dug down -about 4 feet- all around the affected area outside. They filled about 2-3 feet of the hole starting with 2" stone on the bottom and ending with pea stone. They covered this with about 12" of loam watering it down to allow seepage. The idea was to create efficient drainage so that the top-soil would never be saturated.
If you can adjust the grade outside without a huge earth moving effort that might be ideal. If not this approach is better than doing nothing.
In any event, the pressure treated will last quite a long time even exposed to constant moisture.
Mike, years ago they used to make a "below grade rated" treated wood that was a genuine Wolmanized product. It was rated to be used in your application, and for decking on boat docks, etc.
Haven't seen that stuff in years, and they probably don't even make it anymore with today's EPA requirements. But if you could find that, it should last a long time.
But today's treated lumber is rarely more than a low pressure dip of green wood in a pool of mildly preservative liquid. It is better than nothing, but that would be where I would leave it.
I have seen some pretty good preservation from some of the old buildings I have worked on. In some areas where the wood structure was going to flood, they put creosote treated wood (think telephone poles and railroad ties) that had been sawn into rough boards into the wet areas, but scabbed them onto regular wood. In other words, the wet area was scabbed, not the whole piece.
Alternately, when I was a kid we used to put a 1/4" or so layer of roofing tar on fence posts when we replacing posts. We figured out how deep they fence post would go, then went about 6" higher with the tar. That worked great. But it was a fence.
But the real solution is what Joe said. Regrade your terrain to get the joists out of the dirt/water exposure. You need to get the moisture from the dirt and water away from the wood. No wood will ever last a long time sitting in dirt.
Robert
Thanks guys, really useful comments.
Looks like I need to get my spade out then...
Mike
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