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jgibbs 08-01-2013 06:06 PM

Need to rebuild garage storage loft
 
2 Attachment(s)
(New member & don't think m first post posted, but sorry if this is duplicate) The joists under the storage loft in my garage are sagging and I hear ominous cracks and cracks when I stand on it. It appears to have been built when the house was constructed in the late 1940's.* What's more, the joists are 2 x 4s and there are no ledger boards. The joists are set on top of 2 x 4s with no blocking between the joists (see attached pics). The garage is 12' wide and the loft is 12' deep. I'm not going to store stacks of bricks, but I have a lot of garage clutter that I want to get out of the way.

I need an (relatively) easy and inexpensive way of shoring up the joists and stablelizing the loft. I need help figuring out 1) How to add ledger boards to properly support the joists without having to remove and rebuild the whole loft (i.e. rebuild in place); 2) Can I just add heavier joists or do I have to remove the old joists; 3) What size and how many joists do I need to add(i.e. can I add a new joist say every other or maybe every 3rd or 4th old joist; 4) How can I attach the new joists to the new ledger boards without lifting the loft floor boards (e.g. is there a type of joist hanger that doesn't lap over the top of the ledger board?

Thanks for your help.

Joel

joecaption 08-01-2013 08:47 PM

If you want to do this right it's all got to come out and be replaced with at least 2 X 8's.
It would be best if they where sitting on top of the top plates.
You would just have to cut the top of them at an angle to match the roof pitch.

jgibbs 08-01-2013 09:28 PM

thanks
 
As a rule I try to build things the right way. My wife thinks I build everything to survive a nuclear attack. But in this case, doing it the right way isn't practical. What's the best way to reinforce what's there?

Thanks

Joel

GBrackins 08-02-2013 06:56 AM

Installing a beam at mid-span under the 2x4 joists would be the easiest and probably cheapest way of reinforcing. But then you wouldn't be able to park your car in there.

now it depends on how you want to do.

joe gave you an excellent suggestion. you could always sister a 2x8 along side the 2x4 (tops flush) and use some joist hangers on the end. you may need to install some 2x4 blocking on top of the 2x4 that runs under the 2x4 joists so that you can attach the joist hangers.

if you're just looking for anything you could sister some 2x4's onto what's there. it MAY work, but doubtful.

good luck!

jgibbs 08-02-2013 04:00 PM

@Joe - In light of Gary's affirmation of your recommendation, perhaps I misunderstood your comment. When you said I should put new joists on top of the top plates I figured you meant I should tear the whole thing down, since the existing joists rest below the top plate. I'm sure that would be best, but were you suggesting an alternative?

@Gary - Your idea of sistering the 2 x 4s with 2 x 8s is along my initial direction, but I am concerned that hanging the 2 x 8s from blocking on top of the existing 2 x 4 ledger wouldn't provide a strong anchor to the wall since the blocking would have to be nailed/toenailed to the existing joists and a 2 x 4 ledger seems totally inadequate. Am I misunderstanding you, or is there a good way of strengthening the ledger?

Also, the ledger is only nailed to the wall studs. I've read about a special type of screw that is designed to withstand shear forces but is smaller diameter so it won't split the studs. Does anyone know what these are called?

Thanks

Joel

GBrackins 08-02-2013 07:52 PM

I would use something like a Ledgerlok or Simpson Strong Drive wood screw, size based upon loading.

All ledgers should be secured by either the proper number of wood screws or lag screws. I'd install blocking above the continuous 2x4 ledger (what the 2x4 joists sit on) so that the joist hangers would have solid 2x material to be attached to. Secure the blocking into the studs, not toe nailed into the joists. I'd use a concealed joist hanger for the 2x8 joists so that you could attach them next to the existing 2x4 joists, or you could use a face mounted hanger and install the new 2x8's in between the 2x4 joists.

just some random thoughts .....

jgibbs 08-02-2013 11:47 PM

You've been patient and a great help If you don't mind though, I need a few clarifications. Since the existing joists face the studs, to secure the blocking to the studs I guess I'd have to use longer screws and place them at angles toward the stud, right? Also, how do I get the 2nd end of the joist into a concealed joist hanger, since the loft floor prevents dropping them in as you would in new construction?

Finally, someone suggested notching the top of the joists to fit over the ledger and use a 4" hanger on the ledger face, to support 2 x 8 joists? What do you think? Would notching weaken the joist?

tony.g 08-03-2013 06:07 AM

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jgibbs;

Could you just retain the existing joists, and run a 2x4 bearer along the tops (fixed with simpson hangers - 2 to each connection) and then suspend the bearer by hangers off the ridge beam?

It would almost certainly not be to code, and you would have the obstruction of the bearer and hangers in the middle, but it would give some extra strength. at fairly minimal cost and disruption. It would also reduce the load on the side studs. You would obviously have to be sensible in what you put up there

GBrackins 08-03-2013 09:13 AM

use something along this line and install them perpendicular to the face of the stud.
http://www.strongtie.com/products/co...SDWS-SDWH.asp#. at a 1/4" diameter you could install two through the ledger to attach to each stud.

you could install your new joists in between the existing and use face mounted hangers. I am not a fan of notching of joists as it usually leads to a spliting of the notch. you are allowed by most building codes to notch 1/4 the depth at the end of a joist.

hope that helps. ask back with any questions

Pittsville 08-03-2013 01:40 PM

Have not seen it mentioned, but if deflection (sagging) is your concern, you can install a 2x4 flange on the bottom of the joist to help stiffen it up. You would face nail the 2x4 to the bottom of the joist. For best results, you may want to lift the existing joists to remove the sag prior to installing the 2x4s.

jgibbs 08-03-2013 04:35 PM

I am impressed with the willingness of the members of this online community to be so generous with their time and knowledge. Now I have to figure out which of several options to best.

@Gary - I understand that the blocking between the joists has to be perpendicular to the face of the studs. I'm still a little unclear about how to attach them to the studs. The only way I can see is to "toe-nail" the ledger screws into the studs. Is that what you meant? Re: notching joists - It didn't sound good to me either, and the notch would have to be more than 1/4 of the width. And thanks for the tip about the Strong Drive screws.

@Tony - I think it would be difficult to make your suggestion re: bearer and hangers work in my situation. The garage is attached to the house with a hip roof over the garage, so there is no ridge beam over the center of the garage. The geometry and engineering of figuring how to attach hangers to the hip beams and rafters is intimidating.

@"Pittsville" - I found your suggestion of attaching a flange to the bottom of the existing joist interesting, so I researched it online. I don't understand the math of the "modulus" and "moment" but what I got from it is that when a joist sags the bottom of the joist becomes longer than the top. The flange keeps that from happening. I think the technique is to jack up the center of the loft, then attach the flange with construction adhesive and screws. Kind of like building an engineered joist. Sounds like simpler than adding joists.

Can anyone tell me if flanging every joist would add strength roughly equal to adding a 2 x 8 joist for every OTHER joist? Both would use about the same amount of board feet of lumber under the loft, but flanging would involve much less labor.

Thanks

Joel

tony.g 08-04-2013 04:47 AM

Joel,

Unless you pile the floor up with bricks, the joists themselves are unlikely to fail by actually snapping. Your main two issue are 1. excessive deflection and 2. making sure the floor is firmly fixed to the walls.

You've clearly read up on this, and for any given load, span and species of timber, the maximum deflection is always inversely proportional to the 'moment of inertia' (abbreviated to 'I') of the cross-section of the beam. Putting aside all the maths, if you fix a flat 2x4 flange to the underside of each beam as pittsville suggests, you will increase the 'I' of the beam approximately 5-fold, so your deflection would be reduced by about 80%
(very rough figures).

Adding a 2x8 to alternate joists will reduce the deflection a little more than flanging every joist. It would be more difficult to work out - but probably not much in it. Might be easier to flange each joist with the lighter timber.

You would not have to run the flange end-to-end - you can stop it a foot or so short at each end. But they must be firmly fixed (eg coach screws) every 12", plus some adhesive.

(btw, it's not a problem if your floor creaks and groans; as with timber ships, they used to say it's not a problem when the vessel creaks, it's when it stops creaking is the time to worry!).

hand drive 08-04-2013 10:54 AM

how I've handled this type of situation( especially upgrading older homes with huge joist notches) add blocking between joists that are there, might require a plywood shim, 3/8" or 1/2" to match thickness of older ledger and bring new blocking flush with face of ledger. put new joists sistered to old joist and use double joist hanger to catch new and old joist( put a ripped shim along bottom of old joist that brings plane of old joist to the same as bottom of new joist).

jgibbs 08-04-2013 11:34 PM

So....To Tony's point - "making sure the floor is firmly fixed to the walls" - I'm still unclear about part of that. I know how to use joist hangers. The blocking between the old joists that is my point of confusion. As I said earlier, the wall is finished, so I think I'd have to set the screws at an angle toard the stud inside the wall. I know to use something like Simpson Strongdrive 1/4" screws.

I asked before if this is an acceptable method? Or is there a better way? Do I need to open the wall and screw blocks beteen the studs, then screw tge ledger blocks to that? Opening the wall seems like a rather inelegant solution.

I've never done anything exactly like this so I'm at a loss as to whether "toe-nailing" the screws into the studs is good.

Thanks

Joel

hand drive 08-05-2013 08:08 AM

Quote:

Originally Posted by jgibbs (Post 1225166)
So....To Tony's point - "making sure the floor is firmly fixed to the walls" - I'm still unclear about part of that. I know how to use joist hangers. The blocking between the old joists that is my point of confusion. As I said earlier, the wall is finished, so I think I'd have to set the screws at an angle toard the stud inside the wall. I know to use something like Simpson Strongdrive 1/4" screws.

I asked before if this is an acceptable method? Or is there a better way? Do I need to open the wall and screw blocks beteen the studs, then screw tge ledger blocks to that? Opening the wall seems like a rather inelegant solution.

I've never done anything exactly like this so I'm at a loss as to whether "toe-nailing" the screws into the studs is good.

Thanks

Joel

really your blocks between the joists do not need many nails/screws as they will be jammed into place from the new joists sitting against them pressing them to the wall. the blocks will have downward pressure which will be covered by the ledger that sits under them ( consider fortifying the current ledger with more nails/screws). nailing/screwing the blocks at an angle to catch the stud behind the joist is a perfectly normal way to do it and quite possibly the only way if there is nothing solid behind them to nail to, you can even nail back through the original joists into your blocking also. nail through first to the wall to get the blocks drawn up tight and then nail through the old joists into blocks, you will have to angle those nails some as well because the new block will -block- part of the nailing surface when nailing straight through...


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