I am about to do some outdoor work for a family that includes a 16x13' cedar pergola to be built on a 4" thick, stamped concrete slab that is now 4 months old. The ground under the slab is well drained and was thoroughly compacted by another contractor before pouring.
I was told there was to be spread footings poured under the slab where the legs of the pergola was to be. I later found out that this was not done. It seems like my options are:
1) have 4 holes cored through the slab so I can put sonotubes through the slab and set the legs on those. It's not a spread footing, but at least if the structure settles, it hopefully would do so independant of the slab and not lead to cracks. The downside is this would be a bit unsightly, messy, and cost the owners and extra $500.
2) Drill saddles directly in to the slab. I was thinking about it, and the weight of the load of wood I picked up from the mill was around 2000lbs, some of which will be off cuts, some of it will be for a different project. But lets use the full 2000lbs for safety's sake. That would mean there is only 500lbs bearing on each leg. There owners may want to add a PVC type roof in the future, but the weight would be negligible, and we don't really get snow here so I don't think that extra weight would be an issue.
I obviously don't want to cut any corners and have their slab crack but don't want to waste someone's money on something that may not be necessary. What say you?
I was told there was to be spread footings poured under the slab where the legs of the pergola was to be. I later found out that this was not done. It seems like my options are:
1) have 4 holes cored through the slab so I can put sonotubes through the slab and set the legs on those. It's not a spread footing, but at least if the structure settles, it hopefully would do so independant of the slab and not lead to cracks. The downside is this would be a bit unsightly, messy, and cost the owners and extra $500.
2) Drill saddles directly in to the slab. I was thinking about it, and the weight of the load of wood I picked up from the mill was around 2000lbs, some of which will be off cuts, some of it will be for a different project. But lets use the full 2000lbs for safety's sake. That would mean there is only 500lbs bearing on each leg. There owners may want to add a PVC type roof in the future, but the weight would be negligible, and we don't really get snow here so I don't think that extra weight would be an issue.
I obviously don't want to cut any corners and have their slab crack but don't want to waste someone's money on something that may not be necessary. What say you?
