The LAG BOLT "Thread"

[DRC12345]

I performed a search and was very surpised to see that there were no discussions on the usage of Lag Bolts or Lag Screws. I guess this is self explanatory, however, not so much for newbies such as myself

I am in the midst of building a garage storage loft abd am torn between using 4” wood screws or 4" Lag bolts to fasten into the rear and side wall studs? There are so many different kinds so I’m not sure where to start (#10, 12, 14 screws, 5/16", 3/18" lag bolts).

What is the procedure in drilling a lag bolt? Pre-drill one size smaller to accommodate the thread catching but not splitting the wood? Use a drill and tighten manually with a ratchet? Washers required?

For my purpose, what would you recommend?

 

[Mattlt]

They are fine to use, but do not over tighten them. I find them very easy to break off.

When possible, I prefer to use carriage bolts instead (when you can go all the way through) Doesn't sound like you can do that in this case. I would use a lag instead of a screw, especially if it's going to be supporting a loft(?)

To answer your other questions... I don't know, there's probably a chart somewhere that shows what size to use. I always figure overkill is good! I would drill a slightly smaller hole than the lag, use a flat washer, then CAREFULLY tighten with a ratchet.

For fun, you may want to practice in a scrap piece of lumber to see what it takes to break one.

 

[Steve from Socal]

I use lag bolts to support several shelves in my garage, 5/16 and 3/8. I drill the holes to the approximate root diameter of the screws and a bit deeper than the penetration. If a bolt gets tight while running it down back it out a bit and try again, like using a tap where you break the chip. I generally drill the holes and run the lags down right then and back out to confirm a good hole. This makes starting when the bracket or fixture is placed an easy screw in a few threads.

Steve

 

[94legaleagle]

They are fine to use, but do not over tighten them. I find them very easy to break off.

I thought I was the only person who had that problem - so, yep, I second that thought - the head of lag bolts will twist off if you over-tighten them - but I prefer lag bolts to wood screws

just my .02

 

[daveroy]

I thought I was the only person who had that problem - so, yep, I second that thought - the head of lag bolts will twist off if you over-tighten them - but I prefer lag bolts to wood screws

just my .02

Are you guys pre-drilling your holes to small (or not pre-drilling at all) The only time I have ever snapped the head off is when I was stuck without the proper drill bit size, and knew the hole was too small... but tried to 'driver-her-home' anyway...

 

[Frank The Plumber]

I'm not sure how specifically you are going to use lag bolts but I will offer you this insight.

If you take a lag bolt or any other type of screw and drive it into the wood with no pilot hole you actually will have a less strong connection. The wood is shattered and forced out of the hole destroying it's cellular composition. A steel or metallic bolt or screw will have the wood react upon it, after time the connection may be lost or weaken.

I find that you can coat the lag bolt and drill an appropriate pilot hole to minimize the cell destruction of the wood.

I also if I can will use a bit of all thread type rod and make a through bolt and place nuts and washers on each side. In situations where I have a minimum weight I am less worried, in situations where I have large weights motions or vibrations I will use lock nuts and or washers and cinch the through bolt tight.

You can use through bolts and load plates to assemble wood structure very effectively.

Note: If you are snapping the lag bolts it is due to friction, try adding a bit of pipe dope or even a yellow glue while wet to the lags, you won't snap the heads.

 

[ishiboo]

I use lag bolts and screws all the time. I really like the Spax lag screws - they provide a ton of holding power and I can install them easily with my 36v drill. Great for lumber when you have a lot of weight to hold, I also used the grade 5 versions for my 63" plasma mounting bracket.

Lag bolts I always use a washer unless they're truly ONLY for shear. Dimensional lumber has little surface strength and my 36v will sink a 5/16" lag bolt far into a stud before it stops.

 

[DRC12345]

Thanks guys, lots of great information so far! The loft/shelf I will be constructing will be primarily from 2x4 lumber and at a dimension of roughly 3'4" x 8'. The loft will house items such as tires, shopvac, push mower and other light items.

I am a bit nervous to use lag bolts as I definitely do not want to snap any in the process and also damage or split Any of the wall studs. I am instrigued by the Spax structural screws though as I see these carry the same load bearing properties as lag bolts but do not require 2 pilot holes to be pre-drilled.

Basically, I am looking for Strong, Easy , Fast!

 

[csp]

Those self-drilling Spax screws are sweet!

I'm done using lag bolts and have made the switch to structural screws.

More info about them: http://www.familyhandyman.com/DIY-T...ials/Hardware/structural-screws-vs-lag-screws

 

[Frank The Plumber]

I would not bother with lag bolts for this. All of your load is in shear. The ability to carry the load is only as good as the wood. A 2x4 is not so hot. I would use 3 1/2 long wood screws and put load blocks under the parallel 2x4 under each point where the stud is.

Take an 8 or 10 " long piece of 2x4, turn it flush to the wall fit it tight to the stud / joist bottom and attach it to the stud. In this way you will have effectively unloaded the 2x4 and transfered all of the load to the blocks. You will not crack or split the 2x4 joist at the wall. I am a bit concerned about the non wall side. what ya doin there?

 

[Steve from Socal]

The shelf above the machines supports 12-1400 pounds of stuff generally. it is mounted with 3/8 lag bolts and has survived the 1994 Northridge earthquake with no changes. AS mentioned earlier; if you are shearing the heads of lags the bolt is seizing. They are very effective in the proper situation.

Steve

 

[redman43]

I've been using the SPAX structural screws as well. Very nice to just zip them in with the impact driver.

When you factor in the cost of the regular lag bolt + washer, the SPAX are only marginally more expensive. In my opinion, that extra few pennies per screw is well worth it considering you don't have to pre-drill. Plus, I think they're better looking when the screw head is in an exposed application.

 

[DRC12345]

I would use 3 1/2 long wood screws and put load blocks under the parallel 2x4 under each point where the stud is.

Take an 8 or 10 " long piece of 2x4, turn it flush to the wall fit it tight to the stud / joist bottom and attach it to the stud. In this way you will have effectively unloaded the 2x4 and transfered all of the load to the blocks. You will not crack or split the 2x4 joist at the wall. I am a bit concerned about the non wall side. what ya doin there?

See, I have no idea what you are talking about here lol. Do you mean fasten one 8' length of 2x4 to the back wall into the studs and then another 8' length screwed parallel over top which will support the joist hangers, etc?

For the open non-wall corner, I plan on fastening a 4' strip of angle iron spanning across 3-4 ceiling joists (bottom chords) and then a perfed iron strip down to the corner and carriage bolted in at 2 points. Think this will be sufficient? Again, the width will be 40".

 

[brianh]

I have had good luck with Timberlok screws they are a lot easier to use than lags.

More info in link
http://www.fastenmaster.com/details/product/timberlok-heavy-duty-wood-screw.html

 

[Steve from Socal]

I have had good luck with Timberlok screws they are a lot easier to use than lags.

More info in link
http://www.fastenmaster.com/details/product/timberlok-heavy-duty-wood-screw.html

OK Brian,

I am intrigued; how are these a lot easier to use than lag screws? They appear to be a lag screw with a flanged head and flared shank under the head. I could see the convenience of the flange but, I would use heavy washers even with the flange.

Steve

 

[brianh]

They are made out of harder steel, only the first inch and a half or so is threaded so they pull multiple layers together, I used them putting up a log cabin the first time I had experienced them, since then that is all I use.

They power drive very nicely.

 

[Greatbear]

I am a big fan of the Timberlock screws. I drill a hole the root diameter of the threads and have had no issues with broken bolts or sheared heads.

 

[trbomax]

The timberlock screws are a little pricy compared to common lags,but if you need the strength,then they are the way to go. I always pull the lags over a bar of soap to lube them,then run them in with an impact. Ive run literally thousands of them that way building docks,a lot of the time w/o pilot holes

 

[Vicegrip]

I hung all the shelving and blue work benches in the shop with lags driven through the drywall and into the studs. Frank the plumber is spot on with regards to pilot holes. Keps the wood from splitting out and makes driving easer.

 

[DRC12345]

The shelf above the machines supports 12-1400 pounds of stuff generally. it is mounted with 3/8 lag bolts and has survived the 1994 Northridge earthquake with no changes. AS mentioned earlier; if you are shearing the heads of lags the bolt is seizing. They are very effective in the proper situation.

Steve

Those are some heavy duty shelf brackets you got there! Are the fabricated or purchased? How wide is your shelf?

 

[Steve from Socal]

Hi,

They are made up from 3" 3/16 U channel they are 18X18, the shelf is 20" wide 12 feet long 3/4 plywood.

I actually had a couple of small machines stored up there for a while, my engine hoist will lift up to it.

Steve

 

[DRC12345]

I went to Home Depot over lunch and took a look at the Headlok and Timberlok screws/bolts. They have different types in various lengths starting from 3.5" to 6" and 2 different head types, spider design (headlok) and typcial hexagonal (timberlok). Both sets come with a drill bit!

I had my eyes on the 4" lengths and both types were $15 CAD for a pack of 12 bolts. Over a buck each, subtracting the estimated value of the drill bit. Is this a good deal or pricey?

Here they are:

Headlok

Timberlok

 

[mbatarga]

The timberlock screws are a little pricy compared to common lags,but if you need the strength,then they are the way to go. I always pull the lags over a bar of soap to lube them,then run them in with an impact. Ive run literally thousands of them that way building docks,a lot of the time w/o pilot holes

Bar soap, while actually a good lubricant, draws in moisture and causes rust.

I use commode wax rings - they contain beeswax - instead. I've got several old yogurt cups that are full of the stuff that I carry around when constructing wood projects with screws.

 

[59 wagon man]

i don't know if i would trust the perf strap or "band iron" your referring to . a better way maybe a "L" bracket bolted to the ceiling beam with a piece of 3/8" threaded rod then when you get to the shelf you can go thru the corner with a triangle shaped piece of metal under the shelf which the rod goes thru with a nut and washer to hold the shelf

 

[DRC12345]

i don't know if i would trust the perf strap or "band iron" your referring to . a better way maybe a "L" bracket bolted to the ceiling beam with a piece of 3/8" threaded rod then when you get to the shelf you can go thru the corner with a triangle shaped piece of metal under the shelf which the rod goes thru with a nut and washer to hold the shelf

Good suggestion, however, I am trying to understand the "L bracket bolted to the ceiling beam with a piece of 3/8" threaded rod". Wouldn't this be prone to stripping given too much weight?

The band iron I am looking at is pretty thick and it would be bolted to the angle iron spanned across multiple ceiling joists and lagged in with Timberlok or a regular lag bolt and then bolted through the 2x4 bottom with a washer and nut....2 of them actually.

 

[Ign]

Headlok

I've ranted about this before and on general principle try to avoid the Headloks because we just don't need another driver (spider drive). However a #3 phillips will get the job done.

I don't care if they have to pay a royalty or something to use another drive system - it's about customer ease and with tons of proven drive systems out there it's just stupid to invent another one unless you're NASA and it's truly required. Even a standard hex key would work - you're driving into WOOD.

GRK structural screws use standard Torx, which is what I prefer. I believe they're all considered Gr8. It's just hard to find them in shorter lengths like you can with lags. The shortest GRK's I've been able to easily obtain are around 2 5/8" long.

Both Ace and Tru-Values sell the generic TimberLoks - Timber Tites in the individual bins with all other Hillman fasteners. If you only need a couple, it's way cheaper than buying a bulk pack. If you need a larger quantity, it's far more expensive to buy them by the piece.

 

[trythis]

On the topic of head types, I would rather they all be square drive. I have never had one strip. The #3 Phillips often accommodate square and are my fav.

 

[TOOL FANATIK]

I want to bring this thread back to life. What seems to be the best (not best value) structural screw today? Currently I have had experience with GRK RSS, FASTENMASTER LEDGERLOK, and SPAX.

 

[Dennis Leigh Henry]

Sorry to hijack a bit.. I fell into a load of lag bolts way back when my wife and I got married in the mid 1980s, went to an old hardware store closing / auction near Barron Lake, MI. Ended up with a huge box of lag bolts for about $20. I got use to them during my days helping out at the local theater as a stage hand with my dad as the stage manager, all volunteer. Here are a few pictures of what is still around from that.

 

[bob15]

Timberlok screws are the way to go. They are next to impossible to strip out and require zero pre-drilling. Also have a a stronger shear load.

 

[TOOL FANATIK]

Timberlok screws are the way to go. They are next to impossible to strip out and require zero pre-drilling. Also have a a stronger shear load.

Just to be clear you're referring to the black screws right? I use those for 3x5 landscape timbers. They do not have a high shear strength however. I built a tree stand using these and by the next season they all sheared off.
Ledgerloks woulda been the ideal screw for the tree stand.

 

[TOOL FANATIK]

Sorry to hijack a bit.. I fell into a load of lag bolts way back when my wife and I got married in the mid 1980s, went to an old hardware store closing / auction near Barron Lake, MI. Ended up with a huge box of lag bolts for about $20. I got use to them during my days helping out at the local theater as a stage hand with my dad as the stage manager, all volunteer. Here are a few pictures of what is still around from that.

Are those 4 points?

 

[bob15]

Just to be clear you're referring to the black screws right? I use those for 3x5 landscape timbers. They do not have a high shear strength however. I built a tree stand using these and by the next season they all sheared off.
Ledgerloks woulda been the ideal screw for the tree stand.

Yes, that is what I'm talking about.

Here are the specs for them: https://www.fastenmaster.com/tl_files/fastenmaster/download/ESR1078_2015.pdf

 

[TOOL FANATIK]

Yes, that is what I'm talking about.

Here are the specs for them: https://www.fastenmaster.com/tl_files/fastenmaster/download/ESR1078_2015.pdf

My tree stand was built on a black cherry tree with four trunks almost right from the ground. I two by four'd each trunk to the next, but the swaying from the heavier winds was enough to shear those screws. The ledgerloks are thicker diameter screws, the ones I have are 5/16". I like them but there aren't any modifications to the screw itself like we see in the GRK or SPAX screws. My overall favorite structural screw is the SPAX. Their 1/2" screw is monstrous and has saw blades for threads! Larger 7/16" hex head, doesn't cam out like even the torx can on the GRK screws. And the coating on them is similar to the coating NWS uses on their pliers, and I know those to be very good. I want to see a real world shear test on these screws. I think Simpson strontie has tests on the web for their structural screws.

 

[finn]

The GRK type screw seems to have the market cornered here. Common lag screws aren't used, as the high strength structural screw has made the lag bolt pretty much obsolete.

 

[theoldwizard1]

Back to the beginning of this thread ...

I find less and less uses for lag bolts. Pre-drilling is almost always required. The are good when used in shear because they have a large diameter, but too often they are used where there is a large force pulling directly on the head. If the wood they are drilled into is exposed to the weather, even it it is PT, they will likely pull out unless you use more than 1, which frequently you do not have the space to accommodate.

The worst use of a lag bolt is on something that will experience vibration/movement. Even when the load is in shear, that vibration will cause the hole to open (think of a gate hinge applied to the face of a post or the gate itself).

There was a recent thread about hanging a mini-split compress on a bracket bolted to wall. The provide hardware was a hanger bolt (half lag and half USS threaded headless bolt). I don't know of a better way to attach a bracket like this to an existing, finished wall, but I would use at least 3 of them instead of the ONE supplied !

TimberLOK, LedgerLOK, etc. have their place. They are basically just long narrow shank wood screws/lag bolts. Again, they work well in shear, but not when a load is placed in line with the fastener.

 

[TOOL FANATIK]

What kind of load are you referring to that a ledgerlok does not do well with? You suggest they do well with shear wich would mean any gravity loads dead and/or live, or any uplift, that is wind forces pulling up from below. In line loads I assume you're referring to lateral loads, that fight to pull the fastener out???

 

[TOOL FANATIK]

And note, if lag bolts are being pulled from their warm and cozy nesting holes, chances are they were not properly installed. Lag bolts have always been the go to for ledger attachments to rim joists for deck building. If there is no predrill for the threaded portion and then a larger predrill for the shoulder portion they may not hold up.

 

[theoldwizard1]

What kind of load are you referring to that a ledgerlok does not do well with? You suggest they do well with shear wich would mean any gravity loads dead and/or live, or any uplift, that is wind forces pulling up from below. In line loads I assume you're referring to lateral loads, that fight to pull the fastener out???

Exactly ! Most people think that a L-shaped shelf hanger imparts a mostly shear load on a lag. Only 1 lag is really required (at the top of the L). While there is some shear load, there is also a large amount lateral load.

And note, if lag bolts are being pulled from their warm and cozy nesting holes, chances are they were not properly installed. Lag bolts have always been the go to for ledger attachments to rim joists for deck building.

Slightly different application. First most ledgers will use multiple lags. Overkill, in this case, is good. Second, any lateral load will be transferred to the joists which are connected to the cross beams.

 

[reader2580]

Like some of the others, I like the SPAX screws over lag bolts these days. They come in some really heavy duty sizes, but they are not cheap.

As far as lag bolts for ledger boards are concerned some municipalities will not longer allow deck ledger boards to be attached only to the rim joists. They have seen newer houses with the rim joists being pulled loose due to decks. My brother has a 1999 house and he had to put in special hardware that bolts to the joists themselves for his deck. I will probably do the same thing if I ever build a replacement deck at my house.