Thread: new concstrution bouncy floors

I'll be doing a new construction inspection on Friday that is already occupied. It's a two story 4200+sq ft. I'm not yet sure of the design.

The client has already pointed out that he thinks the floors are flexing too much. He said it is on both the 1st and second floor that it does this. There will be some exposed structure in the basement but the majority is hidden by finishing.

How to I judge the amount of floor bounce when I can't see the support structure? I'm hoping I can get some general ideas on how to handle this part of the inspection.

Thanks.

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John, when I have concerns about too much deflection or "give" on a floor surface, I go to the room beneath and have my clients jump on the floor in question so I can observe any deflection. It's not very scientific but it does sometimes give me an idea that something is not right with the floor. Possible causes could be cracked joists, overspanned or undersized joists, or variable OC spacing.

Have your clients go in that room and bounce away. If they fall through the floor, then you know something isn't right .

Originally Posted by John Dirks Jr

I'll be doing a new construction inspection on Friday that is already occupied. It's a two story 4200+sq ft. I'm not yet sure of the design.

The client has already pointed out that he thinks the floors are flexing too much. He said it is on both the 1st and second floor that it does this. There will be some exposed structure in the basement but the majority is hidden by finishing.

How to I judge the amount of floor bounce when I can't see the support structure? I'm hoping I can get some general ideas on how to handle this part of the inspection.

Thanks.

Well, this is really outside the scope of a normal home inspection. About all you can do is to see what the guy is talking about. If he weighs in at 400lbs, I bet the floors are flexing. Heck, I weigh in at 260 and I can make some floor systems flex or feel like they are flexing. He might have a legitimate concern, I have seen it before.

Originally Posted by John Dirks Jr

I'll be doing a new construction inspection on Friday that is already occupied. It's a two story 4200+sq ft. I'm not yet sure of the design.

The client has already pointed out that he thinks the floors are flexing too much. He said it is on both the 1st and second floor that it does this. There will be some exposed structure in the basement but the majority is hidden by finishing.

How to I judge the amount of floor bounce when I can't see the support structure? I'm hoping I can get some general ideas on how to handle this part of the inspection.

Thanks.

Well, tile floors should not have much more than somewhere between a 1/16 and a 32nd movement or you will have cracking. I am sure that you have walked thru a substantial amount of homes in the past. If it appears that there is much more than the norm you are used to then write it up for review.

If there is next to no load on the floors yet such as sparsley furnished then they are designed to move a bit for that guestimated load.

I had the same thing recently where a huge media room was spanning over the kitchen, dinette and living room of the first floor. They had no furniture in there yet and there was obvious give but if there where a pool table at one end and media room couches on the other that would have been taken up. If they are not satisfied with any results you give them then if it is a new home they may have plans and they can take them to an engineer for further review. If it is a less expensive home (or costly)they may have gone to that absolute design minimum which if they did nothing can be done about it.

To measure, take two sticks (1x2 will work, even lattice) place one snug to the floor, push the other snug to the ceiling, slip a rubber band or two where they overlap (having already slipped the rubber bands on before hand), mark the lower end of the upper stick, hold your marker there while they walk around, jump around, whatever upstairs.

The distance from your original mark to the bottom of the mark made with them up there is how much it actually moved.

Expect it to "feel like" it moves a lot more than it really moves.

This will allow your clients to actually see how much it moves with them up there. This may make them feel better about it, or it may make them feel worse (if there is a lot of movement), but it does quantify the movement.

Measure and mark at several locations. Put painter tape on the stick to allow the sticks to be re-used without marks in the way.

If little movement is shows on the stick but it still "feels like" it moves too much for them, they will need to come to some agreement with the builder as to what they were advertised and what they were given. If the builder has a model home, I would always use that as my first double check - did the builder construct the model differently (better) than the other homes, if so, the builder may have some real big problems to correct. If the model moves the same, well, that *IS* what they saw in the model ...

Sometimes (many times) those types of things end up with no good resolution for the client, as: their expectations may have been too high; their builder refuses to do anything; they refuse to do anything except complain about it; the list can go on and on.

Thanks for your input so far. This being a new home it is not on the maps yet so I drove by just to make sure where it was. The inspection is tomorrow.

Just driving by I noticed a couple of things.

1. The vinyl siding is wavey and buckling. I mean it looks bad. Maybe even a spot or two where the locking grooves are popping out from the rows above. I bet it was nailed tight and the normal expansion is causing the buckling. Is there a code reference to help criticize this crappy work, or maybe a manufacturers instruction I can reference to the client?

2. About the roof. You know how you get a pack of shingles every now and then that is not the exact same color as the others? On this roof there was one and it left a telling pattern of how they installed the shingles. The patch goes straight up in a colunm from bottom to top. The offsets where the ends of the shingles ends butt together are just one tab alternaing all the way up and not a step pattern that you see with good practice. Is this installation prohibited? I know it's not best practice but I'm looking for whatever references I can use for ammo if needed.

I'm sure when I inspect this place there will be more.

Thanks again.

I should have done this first. I dug up my JLC Field Guide. In there I reviewed the various methods of shingle offset layout. The "straight up" method, although not the best, is shown in the guide as a recognized method.

I find this to be quite common with builders that are spacing I-joists on 24" centers. On one of my recent inspections they had installed about 20 pre-cast deck piers and support posts in the crawlspace.

. The vinyl siding is wavey and buckling. I mean it looks bad. Maybe even a spot or two where the locking grooves are popping out from the rows above. I bet it was nailed tight and the normal expansion is causing the buckling. Is there a code reference to help criticize this crappy work, or maybe a manufacturers instruction I can reference to the client?

Here's the Vinyl Siding Institure installation manual: http://www.vinylsiding.org/publicati...2007Manual.pdf

The best thing is to say it looks like crap, but that you need them to find out who the manufacturer is to be sure it is crap. Once you get the manufacturers installation manual, you can really lay it on.

Siding popping free may mean they did not pull it up tightly when installing it.

If the siding was installed tightly, you will know. You should be able to grab each piece and slid it back and forth. (unless it is really hot, to where the siding is fully expanded).

The siding may just be "following the wall". This would mean that the siding may have been properly installed, but the studs are bowed.

About the roof. You know how you get a pack of shingles every now and then that is not the exact same color as the others? On this roof there was one and it left a telling pattern of how they installed the shingles. The patch goes straight up in a colunm from bottom to top. The offsets where the ends of the shingles ends butt together are just one tab alternaing all the way up and not a step pattern that you see with good practice. Is this installation prohibited? I know it's not best practice but I'm looking for whatever references I can use for ammo if needed.

That is the slow method of installation, but I would not say inferior. You could argue the fact that it would be more leak resistant as well. The butt joints will be offset further than typical. I think most roofing manufacturers will say that it is allowed, but the pattern will be affected (cosmetic issue).

When I do see this method of installation, I will slow wayyyyy downnnnnnn, because it likely indicates someone did not know what they were doing. There could be installation errors elsewhere.

There are many methods, such as using leveling lasers or even a transom, I've even seen a person use a really long straight edge, but here are two ways I've used... one is simply placing a small nail or pin in the ceiling — in the middle of the room — and hanging a plumb bob from it until it is hovering just little over the floor. You then walk from the edge of the room to the point where the plumb bob is hanging. With a few trips back and forth, adjusting how high the plumb bob is over the floor, you can easily discover the amount of deflection.

Another method is done using two sticks. One is mounted to a wood plate for a base, the second stick is held onto the first with a small spring clamp. The second stick is raised to touch the ceiling and held in place on the other stick with the clamp, and you make a mark where the two sticks meet (at the end of one or the other) then you then simply walk away from the area and the stick is pushed down by the ceiling, because the clamp doesn't have the power to hold it in place. You then measure the distance between where your mark was and where the stick end is now. That is the deflection per your weight.

Originally Posted by Trent Tarter

I find this to be quite common with builders that are spacing I-joists on 24" centers. On one of my recent inspections they had installed about 20 pre-cast deck piers and support posts in the crawlspace.

I too see a lot of 20 - 24" spacing on I-Joist. Sure it will support weight but what about the sub-floor? The installation instruction for the newer OSB sub-flooring gives explicit instructions about running the material with the long side perpendicular to the joists. There will be flex in the floor if the carpenters who put down the sub-floor ran it in-line with the joists. Only fix for that is to add 7/16" to 5/8" underlayment in the across the existing sub-floor. Perhaps if the joists were accessable, you could add blocking between the joists.

Besides that, has anyone seen bridging on I-Joists >= 12" high. If the I-joist is sitting on beams and not attached with hangers, why wouldn't bridging be required as it is on 2x12 dimensional lumber. Seems to me the old guys put in bridging with just about any floor joist including 2x8, 2x10.

Originally Posted by John Dirks Jr

I'll be doing a new construction inspection on Friday that is already occupied. It's a two story 4200+sq ft. I'm not yet sure of the design.

The client has already pointed out that he thinks the floors are flexing too much. He said it is on both the 1st and second floor that it does this. There will be some exposed structure in the basement but the majority is hidden by finishing.

How to I judge the amount of floor bounce when I can't see the support structure? I'm hoping I can get some general ideas on how to handle this part of the inspection.

Thanks.

Floor joists or trusses are allowed per code to deflect under loading up to a maximum amount equal to a ratio of the length/240 under total load and length/360 under the live load. Let's look at an example of a 30' span. 30ft * 12 in/ft / 240 = 1.5" of deflection is allowed under total load. 30ft * 12 / 360 = 1" of deflection is allowed under live load. Now understand that you are not usually loading the trusses for their full design loading of the typical residential floor loading of 55 PSF load (40 live + 15 dead). So in most cases you #1 are not at full design load and #2 the trusses or joists are not right at the maximum limit. Still you might get 1/4" of deflection under typical conditions if you walk in the center of a long span - IMO 30' would be along span for a floor truss, and 20' would be a long span for a 2x joist.

Concerning the spacing of 24" - the majority of floor trusses are always 24". Most sheathing is rated to span this distance, but it will deflect between the trusses or joists similar to the calculation I noted above. This deflection gets added to the effect noted above.

One of the reasons floors ar perceived as "bouncy" is that when you walk along one joist deflects relative to the adjascent one. This type of thing is usually addressed with 2x6 strongbacks and/or "X" bridging. This helps to level out the perceived deflection by essentially distributing the load. Here's a page that talks about this: Fixing Bouncy Floors | Reader's Digest | Print Version This is an area that often gets neglected.

Originally Posted by Mike Truss Guy

Floor joists or trusses are allowed per code to deflect under loading up to a maximum amount equal to a ratio of the length/240 under total load and length/360 under the live load. Let's look at an example of a 30' span. 30ft * 12 in/ft / 240 = 1.5" of deflection is allowed under total load. 30ft * 12 / 360 = 1" of deflection is allowed under live load. Now understand that you are not usually loading the trusses for their full design loading of the typical residential floor loading of 55 PSF load (40 live + 15 dead). So in most cases you #1 are not at full design load and #2 the trusses or joists are not right at the maximum limit. Still you might get 1/4" of deflection under typical conditions if you walk in the center of a long span - IMO 30' would be along span for a floor truss, and 20' would be a long span for a 2x joist.

Concerning the spacing of 24" - the majority of floor trusses are always 24". Most sheathing is rated to span this distance, but it will deflect between the trusses or joists similar to the calculation I noted above. This deflection gets added to the effect noted above.

One of the reasons floors ar perceived as "bouncy" is that when you walk along one joist deflects relative to the adjascent one. This type of thing is usually addressed with 2x6 strongbacks and/or "X" bridging. This helps to level out the perceived deflection by essentially distributing the load. Here's a page that talks about this: Fixing Bouncy Floors | Reader's Digest | Print Version This is an area that often gets neglected.

That is about the wisest thing one can tell someone for the bouncy floor feeling. Most floors are not constructed as they once used to be automatically. It also use to be 1x material for a subfloor at an angle with full 3/4 flooring on top or a layer of 3/4 plywood with a second layer of 1/2" on it for carpet or tile along with bridging.

Ah, the good ole days. There were actually some pretty decent framing and flooring methods from the past (I did say some)

Bouncy floors are also from framing to the minimum standards. I always went to 2x10 when 2x8 was called for or 2x12 when 2x10 were called for. A relatively small expence for much better quality. Labor was still the same.

Regardless of how much bounce there is, what do you think of these pictures?

We got poor bearing, no end support, spliced joists where there need not be, holes bored too close to the edge, 2x4's sistered to try and correct....the list goes on.

John,
Great photos, and it probably answers the question about the bounce. It was framed by Frick & Frack and they had no idea what they were doing.

Too bad they are already living in it. But on the bright side, you may get an expert witness job out of it. I see this one going to court if they already bought it.

That also looks like SPF (commonly called "white wood" in the Big Box stores) and not SYP, SP, or DF ... SPF is just not as strong as the other species of wood.

I wrote it all up and included the pictures. I recommended a P.E. look at it all...and so on. I mentioned poor quality materials and workmanship too.

Here's the odd thing, this side was under the kitchen and it was sagging before they went in and tried to patch it up. The kitchen usually has heavier loads. The floor structure on the other side of the house which was just a corner room of the family room has doubled joists on every span.

Is it possible that when they built the house, they looked at the plans wrong and doubled joists in the wrong area?

Originally Posted by John Dirks Jr

Is it possible that when they built the house, they looked at the plans wrong and doubled joists in the wrong area?

It is possible that the house was built as "reversed" or "mirror" from the plans.

Some AHJ allow (or at least used to allow) "Reversed" and "Mirror" plans to be submitted, however, most AHJ now recognize the great potential for errors when building from "reversed" or "mirror" plans that they require regular plans be drawn and submitted.

"Reversed" plans typically means the 'you build this plan *reversed* from that shown. One example might be a townhouse where there is a model A and an AR and the AR is the reverse of the A, or even in a single-family home development, two adjacent homes may be A and AR, with the same plan submitted for both.

"Mirror" plans typically means that the plan itself is shown as a mirror image of the other plan, all dimensions and everything is "mirror image". At least with mirror plans the actual layout is shown correctly, but try reading all the dimensions, the notes, etc.

With most plans draw on computers today, there is absolutely no reason to submit or accept "Reversed" or "Mirror" plans, let the person drawing the plans reverse the plans, then reverse the text within the drawings. What you end up with is a proper plan with the text readable the right way. Easy to do with computers, in the old days the excuse was 'but I have to draw another complete set' and the answer should have always been 'Yep, guess you do', but some would say 'Okay, I'll try to work with it'. Leads to too many potential problems.

Originally Posted by Jerry Peck

That also looks like SPF (commonly called "white wood" in the Big Box stores) and not SYP, SP, or DF ... SPF is just not as strong as the other species of wood.

SPF is a lumber group rather than a species. It stands for Spruce-Pine-Fir and uses the lowest design values from each species. Many people prefer it for some framing because it is cheaper, lighter, splits less, and is often much straighter. You are right though, it does not make a good floor joist, but I see no issues using it for wall studs or blocking. For visually graded materials it can have almost half the bending strength as SYP or DF of the same grade. For truss applications SPF that is machine stress rated is often used and has essentially equal strength to DF or SYP of the same grade.

Originally Posted by John Dirks Jr

Regardless of how much bounce there is, what do you think of these pictures?

We got poor bearing, no end support, spliced joists where there need not be, holes bored too close to the edge, 2x4's sistered to try and correct....the list goes on.

You pretty much covered it all...although there seems to be issues with that wiring, too. Any of those is reason enough to flag this for requiring a repair.

Originally Posted by Mike Truss Guy

SPF is a lumber group rather than a species. It stands for Spruce-Pine-Fir and uses the lowest design values from each species.

Mike,

I am aware of that, as I stated, Spruce (the species) Pine (the species) Fir (the species) "SPF is just not as strong as the other species of wood".

I was not stating that "SPF" was a single species of wood, only a group of species commonly lumped together because of their similar strengths (or lack thereof). Thus my reference to "white wood" at the Big Box stores as they frequently label and call SPF "white wood".

They are a lot of first time home builders out there , Ive seem some real night mares , they bought a how to book and took off, couple cases of beer for the buddys for the week end and watch out. Make sure your e and o is up to date, ha ha.

As far as the screwy looking wiring is concerned, they cut short pieces of NM and used them as straps to hang the bundles of other wiring and pipes and stuff. I never saw that before but thats what you see, the top part of a makeshift hanger made of NM.

I might have missed it reading through this thread, but if it is new construction, most building permit offices require engineered and sealed drawings to issue a permit. Refer back to them first. Now that certainly does not mean it was properly inspected . . .

JLMathis