too much weight for a masonry porch?
cutter1971
| Posted in Construction Techniques on
I’m adding onto my house and plan to have a reccessed friends porch that is 6′ deep x 12′ wide in dimension. A brick/block foundation wall runs on the outside 12′. On the inside (reccessed 6′) double 2×10 joists support the recessed wall of the porch. I want to have the floor of the porch made of brick pavers. Can I bolt a steel lintel to the 2×10 joists, add corrugated steel to span the 6′ and pour concrete to form a base for the brick pavers. Will that be too much weight for the angle iron bolted to the joist to support? On the other side it will rest on the foundation wall, so no concern there.
Replies
How much is too much..........
The how much is what you'd have to know to figure the answer to your queston on whether the dbl 2x10x12' (?) beam that may already be holding X amount of weight from the wall / roof that's on it already. That is in addition to whether the "6' of corr. steel" wouldn't buckle from the weight of the concrete.
You should get it engineered along with the bolt pattern for the steel angle if that is considered the way to go.
I'm not sure what a friends porch is, could you explain that? Thanks.
Is there a reason that the porch area which will have pavers on it isn't backfilled and poured?
How much is too much
The joist doesn't support any weight of the roof, just the wall.
It is built with a crawlspace (~ 3 ft off the ground) that is currently completely open . Think of a 36 x 24 rectangle with an open crawl space, then take 12' of wall (on the 36' wall) and indent 6'.
A friends porch is a side or rear entry to the house. One that a friend/neighbor would use as it less formal but more functional as opposed to the front entry, which tends to be more formal (at least in our house) and further away from the important part of the house (ie the kitchen)
just sitting here thinking, No.
Sorry, but I think not. You could have well over 3000 lbs of concrete, the steel decking, the pavers, the wall and the floor on the other side of it (it's dbled up for some reason-perhaps the other 6 ft of floor on the other side of the beam)?
Other questions for you to get an answer for (if I understand the frame correctly) is what is holding up the dbl 2x10 beam? I'm supposing it sits on the foundation on one end, does it sit on a pier or is it tied to another beam at the other end?
This all sounds simple but you're not just putting down tile on a well supported floor. The easy answer is you need someone with good figuring structural load experience to answer your question-which could be construed to be an engineer. I realize you're not building an office tower, but except for the size-the numbers all produce the same result-the correct answer.
Best of luck.
I'm no expert ... but some additional food for thought. You lack some details here. Running perpendicular to the 36 ft, I assume you have floor joists (spacing? size? ... are these all double 2x10s??). spaning the 18ft (24 ft - 6 ft).
Your 18 x 12 area poured w/ e.g. a 4 inch slab would be almost 10,000 lbs. A significant amount of weight. That is w/out the brick which will add maybe what another maybe 8,000 lbs to that.
Is this exposed directly to rain/weather elements? You want a brick floor, but it seems like way overkill. One option might be e.g. a double layer of PT plywood and put the brick on that. Another would be to use e.g. faux brick that is about 1/2 or 3/4" thick and use that. I've seen it used in commercial construction ... looks, feels, well it is real brick, just more of a veneer product than a full thicness brick.
It just seems like a huge amount of effort/expense for maybe this relatively small affect you are shooting for.
An 18ft span is pretty significant. I saw a garage floor slab poured over wood framing before (occupied space below). I think they had 2x12 joists 12" oc for that.
Why not just floor tile? If you want the brick look ... and you do the concrete, why not grid the concrete and acid etch it to give the brick look to it ... saves the weight of the brick.
You have to be concerned not only of supporting the joists at the far end, but also the ability of the joists themselves to carry the load.
Will the porch be exposed to weather?
Generally not a good idea because of the likelihood of leaks, sooner or later.
You should be able to find steel deck to span the 6' without too much problem and a steel angle can be sized to provide continuous support. This would involve a fair amount of welding by the way - both puddle-welding deck edges together and welding the deck to the angle. You could consider using lightweight concrete (115 PCF, IIRC) and brick-like frost-proof tile, which would ease the load somewhat. However, you don't give a span on the double 2 x 10 joists at the porch wall (if I understand the conditions) and that span might be the limiting factor (not to mention deflection on the 6' deck span.
additional information
Sorry for the confusion....I should've added a picture to start with. As you can see there are piers supporting dropped girders, which support the 2x10 joists. There is enough room on the corners of the pier to directly support a piece of the lintel I was talking about. However I take everyones point that this may be a lot of weight.
dimensions might help
added dimensions to diagram
What is the direction of the joists at the same end as porch?
I would still take a longer look at this. There isn't the weight involved that was just previously mentioned, but for sure there's 3-4 k on that porch floor system (1/2 would be carried by the beam). If the joists behind that porch run the short way (12ft) you only have to consider the porch system and wall/celing (?) on that beam. If that's the case, you could certainly substitute a steel beam for that if necessary..
Best of luck.
Sorry ... pic begins to help ... but still lots of confusion (and/or I'm a little slow). You have a dbl 2x10 12 ft long 6 ft away from the foundation wall. It is supported by a steel beam which is supported along its length under the end of the dbl 2x10. Where are the joists?
I know you are trying to show more ... Also why is your question only about the small area within the larger area? You want to just do part of this porch area?
well...I hoped the pic would help
First I'm focusing on the porch area only as that is the space that leaves me a little confused as to how to best handle it. The rest of the area has enough meat to support all of what I have built (It is already built by the way). I have had the plans drawn up by an engineer, which is probably typical lacks a certain amount of detail. I don't really want to go back to him because quite honestly the process was very frustrating.
I've attached a snap shot of the actual plans to give a better sense of what's going on in the rest of the house. The one on the left is the foubndation plan and the one on the right is the floor plan. Note: it is a 1 story house.
In the diagram I'll start from the ground up in the area around the porch
1..2 piers 6ft in from the foundation wall. The piers are separated from each other by 12 ft .
2 There are dropped girders (triple 2 x 10's .....) that span the 24 ft length of wall: run horizontaly on the diagram
3. On top of the dropped girders are 2x10 joists that run vertically on the diagram. In the area supporting the porch wall the joists are doubled
So you've got 2x10 joists spanning 12 ft at ___ " oc. I'm not a structural expert, but assuming e.g. they are 16" oc, you may not have enough structure to do what you are proposing. The other guy hinted that you may be required to have a stamped structural plan to get a permit. However, if it cost you $2,500, I'd be a bit surprised ... he could sketch this out and attach some notes and provide some calcs for this simple structural situation inside of e.g. 2-3 hours I'd think. I've had a lot more done for a lot less recently by a structural w/ far more complexity than this.
But ... you haven't answered my/our other curious questions ... why do you feel compelled to do what it is you've proposed? Inquiring minds want to know ... OK we really don't have minds ... that's why they are inquiring. ;)
I'm compelled because...
I (or more accuratley my wife) would like it to match my front porch, which has a floor of brick pavers placed on a raised concrete bed.
2x10 joists are 16" OC
Also I already have my permit in hand for the structure, as this is an addition for ~1000 sq ft. Everything is roughed in now. The plans , which were drawn up and stamped by a structural engineer, were not very descriptive about the configuration of the porch and I'm guessing the engineer took the liberty of assuming it would be a wood porch.
Stamped plans w/out specifying the basic details of the porch or an indication the porch would not be his responsibility is odd. So why not ask that engineer?
Your wife's desire is much respected. Did you consider my other suggestion to use a brick veneer over e.g. double layer of plywood? It could look like pavers, but be [relatively] feather light. An engineer may save you the added cost of simply overdesigning the thing and the heartache of underdesigning it.
Back to the engineer anyway
I thought if I went down to the inspection and permit office with my own drawing they would give the thumbs up. Turns out they want me to go back to the engineer, which I did. He says it's not that complicated and he'd take care of it.
I haven't given a lot more thought to the brick veneer more or less because I wonder how much flex there will be in the floor and how weather tight you can make it. The concrete work would be be unaffected .
Maybe you can still consider brick veneer over the concrete to minimize the weight (and cost). The brick veneer I've seen is very nice. You may be able to get away w/ thinner concrete.
You can, but do you want to?
The porch system you describe could be engineered, and built. But, will probably require additional load supporting members. If you have access to the crawl space it will be relatively easy to design a support system. Depending on the foundation wall design, those walls may need bolstered to support the load.
So, yes you certainly get something designed that will work. But it will cost quite a bit, and as it is definitely a nonstandard construction, the AHJ will most probably require a design sealed by an Engineer, which will add $2500 or so to the cost.
So what would be standard?
Just curious what the standard approach to making this porch would be?
I do have crawlspace access...nearly 3ft
"Standard Approach"
To me there isn't a "standard" way to do this. But, there are several design options.
The reason I asked about a crawl space, is that it gives a designer lots of latitude on spacing, and sizing for support columns, (you can put them wherever you need and big as you want with out an aesthetics issue), as opposed to a basement where post sizing, and location are effected by, and effect, the floor plan of the basement.
If building over a crawl space I can design in eight inch concrete columns, or steel pipes, anywhere I want. And, I can put them on a grade level concrete beam, or spead footings, and not have to worry about what the architect, or interior designer think.
Unless there is a bomb shelter underneath, pouring concrete to place pavers on seem like 10x overkill. There are several accepted systems available that would allow you to tile (porcelain or stone) your porch without adding 6000 lbs of concrete and a $2000 engineer's stamp to your structure.
YMMV
I'd like to know what those systems are
I'd love to hear how you'd finish this out....I'm open to all possibilities. My wife is open to 1 (brick pavers)
Light weight concrete porch deck
http://forums.finehomebuilding.com/breaktime/construction-techniques/best-exterior-balcony-deckcovering
Now that you've posted a diagram it's possible to see that the plan violates one of the primary principles of foundation design - that the basement/crawl space/foundation wall should directly follow the line of heated space above.
I haven't checked this post in a week or so. So I may have forgot a key item.
However, I'm not sure I agree with your statement. I don't think there is any rule spoken or assumed related to foundation walls following the line of the heated space above. You put the foundation where you need structural support. A recessed element of the exterior wall that e.g. allows for a small porch may have a structural line that follows the outer edge of the porch rather than the exterior wall of the house ... e.g. if roof trusses extended over the porch. The two walls you show may very well be non bearing walls. Even if they were, they may be accomodated w/ beams under them rather than a continuous footing/foundation ... much as you would do for a central load bearing wall running through a crawlspace. The single outer foundation wall line would be far less expensive than the two wall configuration you refer to ... 3-4 fewer corners and less length.
Most people would likely do it the way you are saying, but that doesn't mean it HAS to be done that way.