weld broken on the slide - common??

Yes, they do break from normal wear and tear. Especially the older models that were built in the early 2000's when aluminum frames were becoming the trend.
And the tree branch probably contributed to an already broken or cracked weld.
The duct tape residue over the crack side paneling says that damage was pre-existing. Plus the aged oxidized edges of the paneling say that it's older damage.

wnjj, I'm not sure what search you are doing. If you are finding a handful of posts of different brands, I'm still not calling it "common".

This thread has generated two examples including one very old Fleetwood that uses an entirely different structure, and a longer Host that was heavily used including one episode of hitting a tree if I remember right. I'm not saying the tree is related. Ok, that it was heavily used, but extra unsupported length would be significant.

Still, there is no way to tell if any damaged slide or structure was heavily loaded or not or operated unlevel, or unsupported. Anything can break, for sure, but a handful of cases of damage caused by unknown causes isn't "common".

It seems to me that a limb hitting the top of the outside edge of the slide would be significant force. How much force should it take to break? Who knows?

That is some pretty significant and obvious damage.

Was the damage there before the tree hit? If yes, then the tree didn't cause it. If no, the tree caused it.

I have a 2006 Yellowstone double slide. It is obviously longer and heavier than yours, but in my case the answer is yes. I have had a crack similar to yours for some time. We also had the rear corner weld where the generator is located to break, but this was likely caused from something else and was fixed years ago.

Recently, last October after returning from a long trip from which my slide room bound up badly, we disassembled the lower side wall areas under both sides of the camper. What I found was very surprising regarding the design and construction of the frame systems of this camper ( I do not know if yours is similar or if you would have similar problems with it being a 9.5'). When we took off the 3/8" wood " I- beam " spans located on the lower sidewalls under the two slide rooms, I discovered what I found to be very inadequate design of the lower structure. (NOTE: The structure above this was perfect!) In fact, what was seen,can be generally thought of as an 11' rectangular 1" box aluminum frame, on each side, without any vertical struts along the span. The 3/8" plywood "structure" was screwed into this frame which caused more stress points and facilitated cracking/breaking (all unseen) from flexing . The lowest span nearest the truck bed was cracked or fully broken in multiple pieces and fell out when we removed the plywood overlay. The aluminum cross spans under the camper to the other side were also broken. If we had not had the camper on a table, the entire floor would have fallen out. My conclusion was that the plywood side pieces were all that was holding it together. I am amazed I made it as long as I did on my last long trip (7300 miles)

An effective repair, I think, was made. I have had no further issues since, but I have not taken another month long road trip either. FYI. the repair involved building a lower welded steel frame box along these side lower base areas and spanning across, with angle, the front portion of the camper and flat steel strapping welded along the bottom. This process kept everything in compression and attempted to tie the bottom broken aluminum welded spans to the flat cross members. We also welded a steel frame side box overlay of the 11' aluminum framed box described above. With steel rather than aluminum, we then welded new vertical struts on these side frames to stiffen it up from flexing over the long 11' section and then replaced the 3/8" plywood "I- beam" approach with 3/4" plywood and tied it all into the steel frame to further stiffen it.

After all of this the slide has been smooth and not been a problem. It is my feeling, without a great deal to back it up, that the Yellowstone model because of this original design was problematic. I knew something was wrong when I took my long trip last year, and felt it had to do with the length of this particular camper, which is why, when I toured Host's facility and talked to Randall I expressed interest in a "shorter" floorplan camper.

FWIW Conclusion/Opinion :Not sure if this helps you, but I assume the design strategy of the Rainier is similar to the Yellowstone at this time. I know Host has significantly improved their designs, after talking to Randall and I am considering getting another, so I am not bashing them just telling you what we saw. Your unit has smaller slides and might not experience the same flexing loads as ours. However, the corner side crack in the slide room might be the indication of the beginning of a similar issue.

Wow, look at all that wood! Did you seal that up before you finished the restore?

Aluminum frames can and do crack, especially under slides. That branch didn't look big enough to do anything. The worse stress is from the slide sitting on the frame while bouncing down the road.

A quick Google search will turn up Host, just like my Eagle Cap brand, with cracked frames under the slide.

Forum photo posting is playing trick on me,
so here is final repair.

Since the first post you made about it, I start restoring front wall of my Fleetwood and looks like yes- the poor welds on aluminium frame are industry standard. Knowing how the industry works, I would be not surprised all aluminium frames come from the same shop and are wrapped with different brand skins.
Here are some pictures how I fix my issue.


Click For Full-Size Image.


Here is close up on the weld. Yes, that teardrop is all the weld it was. I found a bit more on the other side, but it all was cold weld, that come off without penetration.
Your weld looks like cold weld as well. Those have the strength of bubble gum.


Click For Full-Size Image.

I think the question should be "is it common on a Host slide?" I'd say no. My 2006 Host is similar in age and is fine. Feel free to search the archives and see what you can find. I'm pretty confident that there is almost no history other than a couple of cases of obvious damage by the user/external forces.

Every manufacturer and also every iteration in each brand is different. It's similar to saying all engines fail. Sure, but you need to be a bit more specific.

In your case, you have a hit that could have caused the failure. I think that's more likely than wear/tear. It's not like anyone can tell how much your slide has or hasn't been used. The slide doesn't have an hour meeting.