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mrshan · 05-09-2006, 03:01 PM

Hi !

How to build and mount a shelf?

Here are the details -

Basically I trying to build a floating shelf to put my home theater receiver,dvd player,x-box and cable box. I already have a 42" plasma tv mounted on the wall and this is gonna be below it. An example of my vision is found in this pic http://tinyurl.com/dztlr
Here are the specs -
Total weight of all the equipments - 40lbs *but i would like it support double that amount because i would like place some decor on the shelf as well.
The height I am looking @ is 8 inches
Depth - 18 inches
Width/Length - is something I am still trying to decide but it might be 6 ft or maybe 5ft.
I was thinking of getting some wood and construct it myself. But now i need some advice on where to begin and how to make it strong enough to support my contents. I definitely am gonna mount it to the studs. I also need to know what tools I need and which type. For example I was trying figure, which was the most powerful type of screw, lag screws or deck screws or any other type? Then I thought of my kitchen cabinets, as they hold heavy ceramic plates/utensils/glassware and are mounted to the wall too. So i could use the same technique and mount my shelf. But i don't know where to start or what to do. So whatever advice or tips you all can provide me will be very helpful. I am basically worried about its strength and reliability the most.
**additional detail** i noticed when i mounted my tv that my drywall is actually double, maybe because its the wall separating me from my neighbour**
Thank you all!

Square Eye · 05-09-2006, 06:22 PM

The boxed type of construction in your link is easier to support than you think. The main load and support points are;

1. the bottom of the shelf, where it meets the wall, this point is the fulcrum of the leverage. Gravity will apply steady load on the shelf and since it is attached only on one side, the bottom will actually be pressed firmly against the wall. Since there is no tension, shear will be the main force you will have to deal with here.

2. The top of the shelf where it meets the wall. The load here will be tension. The pull of gravity will be equal across the shelf, but the attachment will be on one side, so the top of the shelf will be pulling away from the wall as gravity tries to pull the shelf down. If you take care of the down force (shear) at the bottom, then the top will only be affected by tension.

The shorter the box, and the further it reaches from the wall, the more strength will be required to hold the shelf. It's like moving the pivot point closer to the work, it will take less down force to compromise the fasteners.

How would I build it?

I'd go lag bolts, 1/4 x 5" with fender washers. Mount a straight 2x8 on the wall, level, with lag bolts into the studs, pre-drill every hole, a full 1/4 in the 2x8 and 3/16" into the studs. Center the bolts one inch from the top and the bottom. Catch every stud you can find. Finish all of the interior surfaces now with paint or laminate. Then 1x8 sides, level them carefully at the top before attaching them permanently. Then attach the top, the bottom, put some 1x8s in now from front to back with 2" holes drilled to run your cables through, then the front. Built on the wall, the attaching point will be easier to get right and the damage will be minimized from drilling and attaching. Finish the exterior after it's assembled.

Someone will undoubtedly try to sit on it someday. The lag bolts may hold up, but you'd better knock them off before they break it. The leverage will be the depth 18" to 7" the distance from the bottom of the bottom of the shelf to the center of the top bolt. That's 2.57:1 leverage. Pretty steep number, but lags will hold. The 2x8 will likely split where the screws fasten the top, before the lags will pull out.

We've got cabinet makers here, where are you guys? I've built a lot of cabinets, but I don't claim to be final authority. See if someone else will respond with a better way to do this and maybe we will both learn something.

mrshan · 05-09-2006, 09:07 PM

Thank you very much "Square Eye". I definitely got a better idea now.Thanks for all that!

taconick · 05-09-2006, 11:18 PM

this is actually fairly easy. I would make a inner shelf for the system to rest on with a 2x6 laying flat (perpendicular to the wall) and brace it with some 2x4's at a 45 degree angle. Cut the 2x6 about an inch shorter than the total length of the wall system. Mark where your studs are going to be and attach the 2x4 angle supports so that they will hit the studs and the wall, making the 2x6 ledger level both ways. attach the angle support brackets to the wall with 2.5" drywall screws, then attach the ledger with the same screws drilling at an angle into the ledger and studs. you may want to pre drill for this. Next step is construct a 3 sided box out of 1/2" plywood to cover the inner shelf, finish it and slide it onto the ledger attach along the back with countersunk 1" drywall screws and paint to match. As for your cabinets, they are attached to the wall usually with two 3-4" dry wall screws for each cabinet, so this should more than hold the weight you need, just don't let anyone sit on it.

mrshan · 05-10-2006, 06:34 AM

Thank you "Taconick" .You 've definately encouraged me.

milehigh_woodcrafter · 05-10-2006, 10:33 PM

Quote:

Originally Posted by taconick

this is actually fairly easy. I would make a inner shelf for the system to rest on with a 2x6 laying flat (perpendicular to the wall) and brace it with some 2x4's at a 45 degree angle. Cut the 2x6 about an inch shorter than the total length of the wall system. Mark where your studs are going to be and attach the 2x4 angle supports so that they will hit the studs and the wall, making the 2x6 ledger level both ways. attach the angle support brackets to the wall with 2.5" drywall screws, then attach the ledger with the same screws drilling at an angle into the ledger and studs. you may want to pre drill for this. Next step is construct a 3 sided box out of 1/2" plywood to cover the inner shelf, finish it and slide it onto the ledger attach along the back with countersunk 1" drywall screws and paint to match. As for your cabinets, they are attached to the wall usually with two 3-4" dry wall screws for each cabinet, so this should more than hold the weight you need, just don't let anyone sit on it.

I believe this is what we call a sleeve. Mount a "nailer" to some studs and mount it damn good. Design a shelf to slip over the nailer and tack it in. cheers.

milehigh_woodcrafter · 05-10-2006, 10:43 PM

ok, i went back and actually read the posts and viewed the pics. Mount a "nailer" to the wall (via studs) and set yer boxes over it. Basically, forget about mounting the cab. focus on mounting a nailer (2x4 if you will) and then mount your cabinet to that piece. It's much easier to mount the heck out of a nailer, and hang your
cab on it. If you understand the value of hanging your box on studs, then imagine having a horizontal stud mounted outside the wall (more or less). Search the web for "french cleat" this might be the easiest for you depending on your handiness level. I didn't catch wether or not you're building, or buying pre-fabs, let us know. We'll follow up.

milehigh_woodcrafter · 05-10-2006, 10:53 PM

Quote:

Originally Posted by Square Eye

We've got cabinet makers here, where are you guys? I've built a lot of cabinets, but I don't claim to be final authority. See if someone else will respond with a better way to do this and maybe we will both learn something.

AHEM, tom raises many great points, as usual. However, if your dream is to support 80 pounds max, I wouldn't worry too much. If you hit two studs with two screws each, you'll have four fasteners. Divide your total load by the four fasteners, and you're looking at a shear load of 20 lbs per fastener. I believe the shear rating on a standard thumbtack exceeds that. I agree with tom though, keep people away! If your shelf works for you rated at 80 lbs, good. A 200 lb man on it triples over your load rating, so keep that in mind. I just realized I am basically reiterating what sq-I said, but in different terms. Anyway, good luck.

your cabinetmaker friend,
milehigh

mrshan · 05-11-2006, 06:45 PM

Thanks Milehigh Woodcrafter !

Yes, i researched about "french cleat" and it was very helpful.And i am currently working on a plan for my shelf.And yes i am planning to build one from scratch.One thing i can tell you guys is that i am just getting started and soon i'll will post some pics, a complete plan of my drawing and list all the stuff/tools i am gonna buy.

Square Eye · 05-20-2006, 04:14 PM

For those of you who may have missed the link to Mrshan's picture of what he wants.