As a general rule dealers do not stock screens (except maybe entry level pull downs or very low cost motorized screens. The reason is simple, most screens are very expensive to ship. You can be buying a low cost motorized screen 110" diagonal for under $500, but could have to pay around $100 to have it delivered.
So, most times, if you order a screen, it will be shipped to you from the manufacturer.
I should note there are some exceptions. Some online dealers, I can think of two that advertise with us, Eastporters in Canada, and Visual Apex in the US, import screens they sell under their own brand names. That means they do have to stock them.
If a traditional dealer stocks the screen, they are paying the shipping to their location which they will ultimately pass on to you, along with the cost of shipping from their warehouse to your home. Most 100" diagonal or larger screens have to ship by freight - too large for UPS or Fedex. As a result shipping will normally be $65 - $170 for most large screens. My old 140" projector screen, designed for in-ceiling mounting - weighed well over 200 pounds and cost well over $200 to deliver.
If a dealer stocks the screen, they are paying the shipping to their location which they will ultimately pass on to you, along with the cost of shipping from their warehouse to your home. Most larger than 100" diagonal =screens have to ship by freight - too large for UPS or Fedex. As a result shipping will normally be $65 - $170 for most large screens. My old 140" projector screen, designed for in-ceiling mounting - weighed well over 200 pounds and cost well over $200 to deliver. (OK, that was an unusually heavy screen).
As a result, almsot all dealers will order the screen as needed. Typically allow two weeks minimum for a screen delivery. Figure 3 to 4 weeks for a customized screen (custom drop, or a non standard size.) However, if you are ordering a standard size pull-down with no customization, the manufacturer probably ships within 2-3 days, so your wait is determined mostly by shipping time. In the fall and especially before Christmas, you should anticipate that you may have to wait an extra 2 weeks or longer as many manufacturers will be severely backordered. A couple of years ago, at least one major projection screen manufacturer was quoting January deliveries, by the beginning of November! (So much for having your theater up by Christmas morning!)
For more information on calculating your screen surface sizes click here.
For more information on what to expect in terms of the exterior size of a projector screen, that considers the case, the borders and trim, click here.
Quicktip: If you are ordering a non-standard size, it is normally going to be in the next larger casing. So, for example, if a company makes a 110" size, and the next size is 123", but you order a 114" diagaonal, its probably going to be in the case that is used for the 123" size. The result - you may have an extra 10 more inches of case width than a standard size would have.
Rule number two: Costs for customizing screens aren't that bad. Often a manufacturers will just charge you for the next largest size, and perhaps a flat fee. This will, however, vary significantly, from one projection screen manufacturer to another. So if you really need a non-standard size, ask your dealer.
Rule number three: If you blow it the first time around - and can't use the screen you order - you will almost certainly end up with huge restocking fees. Typically 25 - 30%. Plus freight charges. So get it right the first time! If you are buying a $1000 screen and its wrong, doesn't fit, etc. based on what you ordered, expect it to cost you at least $200-$300 to exchange it!
Quicktip: There are always some exceptions. and In the case of restocking fees, I have been advised that one manufacturer - that sells direct to consumers - Carada, does ot normally charge restocking fees. Perhaps the advantage of being factory direct, is that they can go that extra effort to make sure it's the right screen, thus eliminating the vast majority of situations that require screens to be replaced. Anyway, nice to know someone doesn't charge restocking. (Note they make several screen surfaces - and all are fixed wall screens at this time. here's a link to a review of one we did in early 06. (The same screen we use in our testing room.).
And don't expect the credit card companies to bail you out. My understanding from talking to more than one dealer, is that because of the special order nature of most screens, (and dealers normally treat even standard screens as custom orders - in their buy policies), if you call your credit card company and say the screen doesn't fit, etc., you likely won't get much sympathy. Dealers say it is rare that a credit card company will reverse a charge on a screen, whether it is a customized screen or a standard one (unless it isn't delivered, or turns out to be DOA, and your dealer and the manufacter aren't taking care of it).
Good news: With the better brands - such as Stewart Filmscreen, - Stewart requires the dealer to sign off on a diagram of the final screen, on every screen they build, showing dimensions, materials, etc. Typically, a good dealer will send that diagram to you for sign off, anyway, they should. If they don't provide a screen drawing, you should ask for one. In any case, you should confirm your specifications in writing with the dealer. Believe me, a good, knowledgeable dealer should want a sign-off from you, to protect their interests as well. You won't get a "custom" drawing on some low cost motorized screens, but you can still get a data sheet with outside dimensions, length of drop, etc.
Rule number four: Take your time, do it right the first time, you have to make decisions about size, screen surface, drop, borders, tensioning, diagonal size, cosmetics, etc. If you are talking with someone who isn't on top of all of this (like 80% of the people selling home theater projectors), find, instead, a knowledgeable dealer, and stick with them. The savings in aggrevation are even far more signficant than the extra dollars wasted on restocking fees.