I took out a HELOC on my house to help with financing the initial part of my barn build so I didn't deplete my savings and to cover unexpected over runs. We had about 150K in equity on the house and I took a 90k line out. Interest rate was variable but had a 3.49% floor. I pulled about 70k from it to cover the contractors portion of the build, everything that I have done has been paid cash out of savings to complete it, although it isn't done yet.
When rates were still super low last fall I decided to roll the 70k on the HELOC into a cash out refinance on the house for a 10 year mortgage at 2.25% because I had a feeling the HELOC rate would beincreasing substantially. We had the house appraised and we had more than enough equity in the house at that point to also keep the 90k HELOC open, but with no balance on it. My payment to the mortgage is less than what I was paying for the mortgage and the payment to the HELOC prior, but I decided to keep sending that extra to the principle on the mortgage, so I'll have my 10 year paid off in about 7 years and will own the house and barn free and clear aside from taxes.
As far as the appraisals go, when I had the house assessed for the refi, the barn added $9k to the value of the property, I have over 100K into it as it sits and will probably be around 120k when it is done, granted it was not complete at the time of appraisal. Lack of comparable properties in the area didn't help, and the fact that I called it a "barn" didn't help either, although because it is a "barn" and not a "detached garage", it also only hit my taxes at a value of $2500.
With rates flying up, any type of financing needs to be scrutinized really well as the long term implications mean a lot more money out of pocket in the long run. I got lucky that I built just before things went crazy price wise and I also was able to take advantage of the low rates.