Modifying roof trusses for storage

[JD.]

Hello,

I had my 13' x 22' garage built during the summer. I paid attention to and specced most things apart from the roof. I neglected to think about storage up there.

It seems my roof is built with 4 king posts which don't seem ideal for storage.

What is the best way to remove these and still support the roof? I was thinking of using Queen posts in place of the four king posts.

Are they even needed?

See below images:









Many thanks.

 

[n20junkie]

I think your kinda screwed with that weak looking ridge. Had it been an LVL or double 2x10 or 12 you may have had options.

At a minimum you need to have a collar tie/ceiling joist at every rafter (you don't have a trussed roof, you have a conventional rafter roof).

How much do you want to store up there? With the collar ties, access to the area may be an issue. An engineer/PE/Architect is needed.

 

[readhead]

You don't have trusses. You have a ridge board and that is ok as long as you have rafter ties which you have. The posts in the middle were probably temporary supports while the roof was being framed. Removing the posts isn't a problem but the rafter ties will not support much weight. At only 13 feet you could add more and taller ties and carry a little more weight. Not a lot but some.

 

[JD.]

You don't have trusses. You have a ridge board and that is ok as long as you have rafter ties which you have. The posts in the middle were probably temporary supports while the roof was being framed. Removing the posts isn't a problem but the rafter ties will not support much weight. At only 13 feet you could add more and taller ties and carry a little more weight. Not a lot but some.

Thanks for that.

So add more rafter ties? I.e. Currently they're at every other rafter, so put one at every rafter?

Found another photo:

 

[n20junkie]

The king posts transfer the weight of the roof to the walls. Without them, you need to maintain that transfer. The rafters alone can't do the work because they will just spread the walls, you need to complete the triangle with ties or risk having issues.

The problem is geting the ties in now that its finished. Its next to impossible. The room you need to get them above the wall is now sheeted and roofed.

 

[Muttly]

The king posts transfer the weight of the roof to the walls. Without them, you need to maintain that transfer. The rafters alone can't do the work because they will just spread the walls, you need to complete the triangle with ties or risk having issues.

The problem is geting the ties in now that its finished. Its next to impossible. The room you need to get them above the wall is now sheeted and roofed.

They are not trusses, the "king posts" are just temp bracing for the ridge.

The rafter pairs are self supporting as long as they can't spread at the plate.The joists keep them from spreading.

As far as storage goes, 2x6 on 32" centers have little load capacity, even adding additional to get to 16" on center you will still be under 20psf loading with those spans.

 

[lakeroadster]

I guess the pivotal question for the OP is how much weight do you want to store up there?

Once the required lbs per sq-ft is determined then, simply go to a span table and pick the correct materials.

http://www.southernpine.com/span-tables/joists-rafters/

 

[73RR]

As said, you have a simple framed roof, the ceiling joist/bottom chord ties the rafters together at the plate.
The charts on the above link are quite good. Adding capacity will be problematic and with such low head room how much do you really need?

 

[manwithtools]

Those "king posts" in your case are not doing much other than helping hold up the roof during original construction. If you could install a joist in the missing spaces you could remove the vertical braces "king posts" completely. That should not be that hard to do.

The joists look to be 2x6 on 16" centers if they were all installed, is that correct? At only 13 feet span, the joists (if they were all installed) would hold most anything you would reasonably put up there in the room available. A 10 lb /sf live load is 2860 lb's in your attic based on the referenced span tables. Are you really going to store over a ton of "stuff" up there?

Some other variables in your case; is there re-bar installed along the top of the block wall creating a bond beam? Where are you located?

 

[lakeroadster]

Distributed load is the key... not good storage space for big block Chevy motors..

 

[manwithtools]

The king posts transfer the weight of the roof to the walls. Without them, you need to maintain that transfer. The rafters alone can't do the work because they will just spread the walls, you need to complete the triangle with ties or risk having issues.

The problem is geting the ties in now that its finished. Its next to impossible. The room you need to get them above the wall is now sheeted and roofed.

Actually the "king posts" in this case are not doing much. The real work is being done by the ceiling joists (or ties if you prefer).

Putting more ceiling joists in place is a piece of cake in this situation. They only need 1-1/2" bearing surface on each end on the wall. That makes it super easy to slide them into position.

 

[manwithtools]

Distributed load is the key...

Obviously, that's why it's specified in lbs/sq ft. It's also obvious that you can't get significant items near the eaves due to clearance, so that means most of the load is near the center of the ceiling. You give up some of the total weight capacity because you can't effectively use the entire ceiling joist system.

The joist span tables also use 20 lb/sf dead load in their calculations. Even if he's installing two layers of 5/8" drywall on the ceiling and two layers of 3/4" plywood in the attic floor then he's nowhere near that dead load.

OP, what are you intending to store up there?

 

[Homerr]

Looks like JD. is in the UK. Their codes, wood values, sizes, span charts will be different than US. And if there is a higher snow load too.

JD. - not knowing your exact storage needs, budget, or local codes - I'd suggest adding in a ridge beam under the ridge board and the ceiling joist/ties can be removed for a fully vaulted ceiling. Or leave them and add plywood on to them and remove the king posts, they will act as simple joists then.

 

[manwithtools]

Hmm, JD is asking about storage in the attic I think. Not sure how a vaulted ceiling helps that situation?

UK has higher snow loading than the US? It all depends on location. This is why it's important for users to have their location in their profile.

If he's in the UK, the I guess there won't be to many big block Chevy's stored up there, will there

 

[JD.]

I guess the pivotal question for the OP is how much weight do you want to store up there?

Once the required lbs per sq-ft is determined then, simply go to a span table and pick the correct materials.

http://www.southernpine.com/span-tables/joists-rafters/

It will mainly be used for storing junk to be honest!

Those "king posts" in your case are not doing much other than helping hold up the roof during original construction. If you could install a joist in the missing spaces you could remove the vertical braces "king posts" completely. That should not be that hard to do.

The joists look to be 2x6 on 16" centers if they were all installed, is that correct? At only 13 feet span, the joists (if they were all installed) would hold most anything you would reasonably put up there in the room available. A 10 lb /sf live load is 2860 lb's in your attic based on the referenced span tables. Are you really going to store over a ton of "stuff" up there?

Some other variables in your case; is there re-bar installed along the top of the block wall creating a bond beam? Where are you located?

Yep that sounds about right. I wouldn't say I would be storing anywhere near a ton of stuff up there. Probably 500 pounds of stuff at most.

There's no rebar. They are done like this:

Obviously, that's why it's specified in lbs/sq ft. It's also obvious that you can't get significant items near the eaves due to clearance, so that means most of the load is near the center of the ceiling. You give up some of the total weight capacity because you can't effectively use the entire ceiling joist system.

The joist span tables also use 20 lb/sf dead load in their calculations. Even if he's installing two layers of 5/8" drywall on the ceiling and two layers of 3/4" plywood in the attic floor then he's nowhere near that dead load.

OP, what are you intending to store up there?

Probably about 500 pounds of stuff at most.

Looks like JD. is in the UK. Their codes, wood values, sizes, span charts will be different than US. And if there is a higher snow load too.

JD. - not knowing your exact storage needs, budget, or local codes - I'd suggest adding in a ridge beam under the ridge board and the ceiling joist/ties can be removed for a fully vaulted ceiling. Or leave them and add plywood on to them and remove the king posts, they will act as simple joists then.

Hmm, JD is asking about storage in the attic I think. Not sure how a vaulted ceiling helps that situation?

UK has higher snow loading than the US? It all depends on location. This is why it's important for users to have their location in their profile.

If he's in the UK, the I guess there won't be to many big block Chevy's stored up there, will there

Yes I'm in the UK. I intend on keeping the ceiling joists in place in order to floor the attic area.

All: Many thanks for your help and replies! This forum is excellent and the willingness to help and give advice is humbling.

 

[lakeroadster]

It will mainly be used for storing junk to be honest! Probably about 500 pounds of stuff at most.

In that case the flooring you install will likely be heavier than the 500 lbs of junk.

Remember, the weight of the flooring, pull down attic stairs, etc. is also part of the total weight.

Distributed load is the key... not good storage space for big block Chevy motors...

Obviously, that's why it's specified in lbs/sq ft.

or Newton Per Square Meter in this case.

What is obvious to us, many times is not at all obvious to others. The old adage about the true meaning of the word assume

 

[manwithtools]

Yes, I understand. That "assume" statement can be quite reflective...

Unless I'm mistaken, it's lbs/sq ft, not newtons per square meter in the UK. You know that assumption thing don't you John?

Or is it Stones / sq. yd. ?

It could be most difficult to get more items into the attic space without some sort of access after adding the additional floor joists that were previously mentioned.

 

[wisconsin hillrod]

I added ties in my garage seems like it was almost identical. I had no issue getting them up there.

I had different goals as my garage was falling over (so I added the W bracing) and I was looking to hang insulation and plywood for a ceiling but same idea.

 

[JD.]

From doing a bit of research and from replies on here it seems I don't need the "king posts" as they aren't doing much if anything.

I will remove those and the long piece of timber that runs perpendicular to the rafter ties. I think it and the "king posts" were just used when constructing the roof.

I will then floor the whole thing using flooring chipboard.

EDIT:

Found the following diagram which refers to the "king post" as a hanger. It also shows a binder which I have too.

 

[lakeroadster]

The "binder" as it is referred to in your sketch is a lateral brace... leave that in place.

Some will say it's ok to remove it if you install some type of flooring for storage... but that won't be true unless the flooring spans the full length of the building and is attached correctly.

I'd be very leary about removing anything, including the hangers.