With the multi-point locking systems, you have the bolt that extends out into the secondary door (or door frame if you only have 1 door) at the level of the handle, you have a smaller "bolt" that extends out of the top of the door into the upper door frame and one that extends out the bottom of the door into the sill. When the lock is engaged, all these bolts are sticking out. If someone engages the locks with the door open then tries to shut it, the bolts slam into the surrounding frame and damage it. Walk into just about any showroom with French doors on display and take a look at the frames (especially the upper frame). That was one of Pella's selling points was that their mechanism was made to push back into the door if the lock was engaged with the door open and you then tried to shut it. After it was shut, the locks slid back out of the door and into place within the frame & the door is locked with no damage to the surrounding frame, sill or adjacent door. If you're worried about not having a multi point system for security reasons, you can always do a regular deadbolt and slide bolts at the top & bottom. Typically the slide bolts will be much longer than the short little bolts on the integrated multi-point system for a higher level of security IMO. My thoughts on this is that its overkill--if an intruder wants in, he's going to find a way--odds are he will just break the glass and turn the locks whether multi-point or deadbolt. Plus deadbolts & slide bolts are easier to remember how to operate--there is usually a trick to engaging the multi-point lock system. I think with my Mom's doors you have to turn the lock a couple times then flip the lever up to engage the lock. Your secondary swing door of the French door set should bolt in place. That's the biggest part of how the primary swing door is secured when locked. Hope this helps!

So far we love our Marvin slider. As spring progresses we've found we can't open it as much - too many bugs! It needed some adjustment at the beginning. A rep came out and adjusted it no problem. Marvin has been fabulous! We have a set of two very tall French doors in another room. After they were installed last fall they were fine. Then we got a lot of rain. Slowly the bottom of one swelled and started hitting the bottom of the other and eventually we couldn't open the door. The Marvin person came, saw the problem, and ordered us a whole new set of doors about 1/8" narrower (these are very expensive doors). When he came back to install them (a few months later due mostly to us) the original doors were fine. He said he thought that might happen (companies use very green wood to make doors so they may take some time to get to their proper size). He left the new doors with us - so we have a spare in case something happens to the others. So far the same person has come back to do all the servicing. He's from Marvin itself. (The contractor also has the store that sold us the windows as a back-up but so far we haven't needed them). He's great - fixed a couple of other small problems. I really feel like they stand behind their products. We're having a lot of problems with our Miele appliances - their service is supposedly great but there's no comparison. Miele is a total pain, Marvin is a total pleasure.

With doors you want to make sure that the threshold of the door is set in sealant and sits solidly on the sub-floor. It's common for this to not be the case, and eventually the threshold bows down and creates a gap where dirt collects and holds moisture. Don't know if this is what happened to you, but it's something to watch for. And like the other guys said, make sure that the bottom of the door itself is sealed properly from the get go. Also, personally, it doesn't hurt to remove the hinges and seal behind them as well.

Don't necessarily want to get into technical detail "debate" but Loewen claims to use Coastal Douglas Fir. The April 2010 Forest Service labs Woodhandbook (http://www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr190.pdf) does NOT test vertical grain DF as a category; Loewen website simply cites the handbook findings and seems to be in ballpark of accurate in claiming that their DF has better performance characteristics to Ponderosa Pine IF I am understanding things correctly. While I am interested in performance numbers and especially glazing performance, I am equally interested in forum "expert" opinions on functionality, customer experience, warranty service, etc. Thanks for any other input. And yes I will seek out looking at more things live, but while that is what I see and touch, it is what is under the hood that probably will have greatest influence on long term satisfaction. Added via edit, and in case like me you need a resource that describes in plain English what some of the measurements mean and in what circumstances they might be important you might find this page valuable the table on that page(http://workshopcompanion.com/KnowHow/Design/Nature_of_Wood/3_Wood_Strength/3_Wood_Strength.htm) also supports claim that DF is stronger than PP.