Lally Column with footing UNDER the slab
My basement has a 4″ concrete slab with with 4″ of insulation under the slab. The lally columns have footings that are UNDER the slab and UNDER the insulation.
A few lally columns are rusting and will be replaced. So need to break through the concrete, cut out the insulation, remove the old columns sitting on existing footing, then replace with new one. Since the bottom of the new column will be under the slab, how to keep it from rusting? And wont the base plate rust as well?? Is there base plate that doesn’t rust? Can I put a vapor barrier on top of the footing, then put base plate and column on top of the vapor barrier, and wrap the vapor column up around the column so that it doesn’t rust? Or will the weight shred the vapor barrier so it won’t work??
Replies
Why not add concrete to top of footing (pining the new concrete to the footing with rebar) and bring concrete up to floor level. Leave the insulation around the new concrete.
Hi, sure I could do that and it would be easier. However that would leave a 3'x3' space around each lally column without insulation. But maybe that is the best option.
However, the previous contractor went through the trouble of putting the footing under the 4" of rigid foam insulation under the slab for energy efficiency. I was hoping I can keep that and still keep the lally dry with some vapor barrier so it wont rust out.
I understand your concern about maintaining insulation while preventing rust. Have you considered using galvanized steel columns? They're more resistant to rust and might work well in this situation. Another option could be applying a rust-inhibiting coating to the column and base plate before installation. However, I'd be cautious about using a vapor barrier under the weight of a load-bearing column. It might be worth consulting a structural engineer to ensure whatever solution you choose doesn't compromise the column's stability or load-bearing capacity.
Thanks arnoldmatt, I'll try to find galvanized steel lally columns and base plates, or apply some coating.
.Thanks designbing, I think I see what you mean. I could make a say 8" diameter footing on top of the original and only lose a little insulation. I'll have to ask the town if I can do that. I'll explain that it is an extension of the lally column.
Look at the hot dipped galvanized, that what anchors are made out of, hover why is it rusting? Sounds like you may have moisture issues. Consider a French drain around your basement/slab.