[Terhongr (OP)]

We have lived in our house for 7 years and it has a 3 car attached garage. When we first moved in, I put my trailer in the garage which had spider nests under it, unbeknownst to me. I have had a spider problem ever since and cannot get them to move out. I have tried several things, so, does anyone have any suggestions for what I can do?

[Hayseed]

Pressurized, poison gas, for a sufficient duration.   Possibly 3 successive times for the spider generations.

[evan_au]

A better solution: Live and let live!

Most spiders are more interested in eating flies than in eating you.
- The fact that these spiders are thriving means that you have a real fly problem, which will only get worse if you kill all the spiders

When a spider occasionally wanders into our house, I get a glass cup or jar, and a sheet of paper.
- Put the open mouth of the glass over the spider
- Gently slide the sheet of paper under the rim of the glass, pushing the spider into the glass, and sealing off the opening
- Take the paper+glass container outside, and shake the spider into a more suitable habitat, like a tree or grass

To me, a garage with spiders is fine.

Do you know that these spiders have a bite which is dangerous to humans?
- If so, a little more caution is recommended
- I have black widow/red-back spiders in my yard, and I don't try to kill them

See: https://en.wikipedia.org/wiki/List_of_medically_significant_spider_bites

[alancalverd]

I'd get a professional to identify the species and, if in doubt, vote for fumigation. My partner was bitten by a black widow a few years ago. The beast arrived in a consignment of books from the USA and caused consternation in the local hospital as they had no record of a serious spider bite in the last 250 years, and they were unable to locate black widow antivenom in the UK. Black widow bites are potentially disabling to adults and can be fatal for babies.

"The effects of a bite by a member of this genus depend on the species, but effects can include nausea, profuse sweating, severe pain in abdomen and back, muscle aches, hypertension and paralysis of the diaphragm, which can cause difficulty in breathing,"

Releasing them to the wild probably won't  work in the USA.

In the United States, they exist primarily in the South and West. They may be found in dark, dry shelters such as "barns, garages, basements, outdoor toilets, hollow stumps, rodent holes, trash, brush and dense vegetation, according to NCSU.

Latrodectus  may be happy in the Australian outback but they are unknown in the UK because they really don't like cold weather. I suspect these critters would return to the garage at the onset of winter (ours had probably hibernated in a storage facility in Maine). Fumigation is remarkably effective.