Screw Recommendations from the Outside and Inside

[floridarandy]

Outside: If I want to fasten something to the outside of my coach what is the screw diameter and length that can be safely used? Should I be looking for a stud in the exterior wall or is there some type of expanding screw/anchor? Weight wouldn't be a big factor, e.g., rail for removable shelf, string of LED lights, etc. Should I use some type of sealant around the hole before/after the screw is inserted? Next, Inside: If I want to fasten something to an interior wall there are a few more variables. a) To in inside wall that is faces directly to an exterior wall; b) To an inside wall that faces directly to an exterior slide wall; c) To an interior wall that faces the interior (say a bathroom wall that faces the interior of the coach rather than outside wall. Same overall questions....diameter, length and type of screw; is an anchor required or suggested; is a stud needed (would only be a lucky factor based on what was being mounted; and finally is some type of sealant recommended when this interior wall faces to an outside wall. Thanks in advance. Randy in Florida

 

[MTPockets]

I would use stainless steel fasteners. Size? Washers? Through bolt? Depends on what and where. How visible is the fastener after attached? Will this item see any stress, weight? Can you tell us what you plan to fasten?

 

[danemayer]

Here's a link to a video that shows how to install window awnings that use a mounting rail. Uses self-tapping screws (size not mentioned), and butyl tape.

 

[floridarandy]

I would use stainless steel fasteners. Size? Washers? Through bolt? Depends on what and where. How visible is the fastener after attached? Will this item see any stress, weight? Can you tell us what you plan to fasten?

I think what I'm asking, and what I know a lot of other owners will benefit from is a general understanding of the typical exterior and interior wall construction methods, i.e., material and thickness and spacing of studs. With a general understanding of typical wall "sections" the type of anchor would then seem to be easier to generalize. Obviously you're either going to screw into the wall material directly (no stud assumed) and get a certain general "holding" power. After some basic weight threshold you'd need a screw with some type of "anchor". I don't know, but am trying to find out, what types of "anchor systems" are general used for exterior and interior.

And, if there are multiple screw/anchoring systems isn't it generally true that its easier to use a system designed to hold more weight than to use multiple systems and try and "fine tune" screw/anchor to specific weight?

Again, what I'm hoping for are a couple of practical anchoring and sealant solutions for going through exterior walls from the outside...exterior walls from the inside, and interior walls where both sides are interior.

So far I've only seen the "typical" RV head screw...self-taping?...used on inside walls and outside walls using only the walls themselves for anchoring (no anchor) and little if any sealant on those screws. As add things outside and inside I want to use stronger anchoring and better sealing.

This type info would make a great STICKY

Thanks

 

[JohnDar]

For attaching to an interior outer wall keep the fastener length to no more than 1 1/4" and you'll be fine.

If attaching to the outside, same length, but I prefer to shoot some caulk into the pilot hole before driving the screw. I prefer to drill pilot holes, even for self-tappers.

Another option for exterior attachments are stainless steel pop rivets.


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[Bob&Patty]

I used small molly fasteners on the inside. I think they were 3/4" in lenght. Your exterior walls are probably only 3" thick. In fact, put a rubber hose on te drill bit so you cannot drill too far in. Some drill bits can grab the material you are drilling and drill right on through and that can be REALLY bad. So be very careful on where and how you drill. As far as fasteners on the outside...you could use a "stud finder" to find the aluminum studs. If you think you need to drill all the way through.....do it where a cabinet is on the inside walls. Sorry, I hate drilling holes in vehicals of any kind. Remember, the exterior wall are made of fiberglass with hard foam inside with a thin sheet of plywood inside. You cannot tighten any bolt toooo tight or you can crack the fiberglass and/or crush the plywood inside. I did make several shelfs for the inside and used the above type molly fasters. They have been in place for 7 years now with no issues. If you just want to hang some light strings outside....either put them on the awning or use the removeable picture hangers stuck on the outside walls.

 

[floridarandy]

Bob and John -

Now we're getting somewhere. Staying with the general condition solutions:

For mounting to the outside of the outside all:

A self-tapping screw (like what I see mounting most everything on the outside from the factory) would generally be OK up to, say a couple of pounds? Where I see something like the channel the awning mounts into I assume those are just self-tapping screws? Does the factory use exterior moly's for anything?

If I'm replacing self-tapping exterior screws, say the awning mounting screws, an assuming no water damage to the wood, should I go u a diameter size or will re-screwing the same size screw (stainless vs original alloy) in the existing hole still be OK?

For mounting from the inside of an exterior wall I understand moly's of no more than 3/4"? I guess that allows the moly to grip the wall as it expands into the foam within the 3" wall?

Is wall thickness on back and sides of slideouts still OK with a 3/4 moly? (Say if I want to mount a small shelf above the headboard on the bed slideout....or a small shelf for my glasses anchored to the ceiling of the bed slideout?

Same size/type moly for interior walls where both sides are inside? Is their a weight limit after which you'd prefer to go through the wall with a bolt, washers and nut on opposite sides of the wall?

Is there a particular moly brand/configuration you prefer, and if so would you post a link or picture so I can see what I'm looking for?

Thanks again!

Randy

 

[floridarandy]

I'm looking at McMaster-Carr to find the screw types we've been talking about.

1. It appears that the "square drive" is a sheet metal screw as I don't see this drive type in wood, plastic or drywall?
2. It appears these square drive screws for sheet metal are pan head only?
3. There seem to be two types of stainless - "316" and "18-8". Which?
4. There are #1, 2, and #3 drive. I assume this is the square drive size. I only remember one size on the RV...anyone know which is most likely?
5. For Lengths, what is he most typical exterior length. I don't have the coach in front of me but memory would point to 1, 1 1/4 or 1 1/2. Which is most likely? The first project is to remove and replace the screws on the top of the side of the coach where the rubber roof terminates in the flat "rail" with the soft plastic cover over the screws.

Still looking for input on my previous post as to appropriate type moly anchors for interior.

Thanks

 

[Bob&Patty]

Randy, a molly fastener is a molly type fastener. Lowes and HD have plenty of them. Most if not all RV square drive screws are a #2 bit. Boy I wish you were here. I'm having hard time picturing what you want to do as to the outside. I have installed a molly type fastener inside the slides...but still used only a 3/4". I believe that a 3/4" molly fastener can be puchased in different thread sizes for weight ratings.

 

[JohnDar]

Try looking at McFeely's or Rockler's website for square drive wood screws.


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[floridarandy]

Here's a picture that will help understand the initial work I'll be doing on the outside of the coach.

My rubber roof is fine but I'm concerned about the drip rail assembly that fits over the end of the rubber roof as it laps over the side of the roof. You'll note that the screw shown holds the end cap of the rail but there are also screws behind the soft rubber cap that fits over the rail. In pulling back that cap I've noted some rust beginning on the screw heads along that channel. My research has shown that as the caulk ages along the top of that channel water can enter behind the plastic cap and eventually, as those screws rust, follow the screw threads into the roof.



Our coach is now 5 years old and rather than replace the caulk I"m going to remove the plastic cap and replace the screws with stainless covered in double sided eternabond that will encapsulate the screw and head. Then instead of replacing the plastic cap I'm going to take a 4" wide length of Eternabond and lap over the edge of the roof into the bottom of the rain gutter. This will strengthen the edge of the rubber roof from chafing and completely seal the entire drip edge assembly so that water running over the roof edge will follow the Eternabond directly into the rain gutter. I'll extend the Eternabond past the end of the drip rail on both ends and seal it to the side of the coach.

 

[floridarandy]

Try looking at McFeely's or Rockler's website for square drive wood screws.

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John - were you suggesting wood screws for the exterior walls (from outside or inside) or were you thinking about interior walls?

Randy

 

[Bob&Patty]

OK, now I get the picture. I still stand by my statement. I would use a new regular steel screw 1st to clear the thread holes. Put some sealant on the threads when installing the SS screws.

 

[JohnDar]

John - were you suggesting wood screws for the exterior walls (from outside or inside) or were you thinking about interior walls?

Randy

McFeely's carries a lot of different fasteners. I'm just suggesting them as a possible source. Rockler's is where I get my square drive wood screws for interior projects.