I’m building my own home. It’s already framed and sided, and I’ve left ledgers for adding joists and rafters for a wrap-around porch. My question turns around foundation.
Because one side of my house has a walk out basement (it will have a porch on half of its side) and because the ground slopes away fairly steeply from part of the front side of the house (which will have a porch across its entirety), I thought of pouring concrete walls as foundation for this area of the porch, using basic piers for the rest of the house, where the ground surface is fairly close to the bottom of the house. This concrete walls would abut my existing poured concrete foundation – the idea is to have a second, additional basement, perhaps just with a gravel or dirt floor, in this area, both to have the extra space as storage/workshop, and also for aesthetics – I think I’d rather have the walls than tall wooden posts.
This idea originally evolved from a concern about the cost of the posts – on the walkout side of the house and where the ground slopes away – they would have to be at least 16′ tall to run from piers to the porch roof, which could get expensive. Of course poured concrete is too but it would give me the advantage of having more enclosed space.
My question is, what is the best kind of planking to use for the porch floor in the area above this proposed secondary basement? Obviously t-and-g, to prevent water from getting in the basement. Or would it be better just to forget the second basement, using spaced planks as flooring (as on a deck), and possibly just pour very tall concrete piers to get around the necessity for/aesthetics of tall posts?
If I do pour concrete, what is the best way to have the new walls to meet the existing concrete walls (I would use my local concrete contractor, but I want to check here to make sure he’s doing it as it should be done) – does there need to be a slight gap? Also, as the footers for the new walls would have to go over the drain to my septic, can I have the concrete poured around it?
Finally, until I get the porch built, what is the best way to flash the gap between the top of the rafter ledger (2×10) and the bottom of the siding directly above it? Slip flashing underneath the siding and then nail it to the ledger?
Thanks, earthscaper
Replies
Greetings Earthscraper,
This post in response to your question will bump the thread through the 'recent discussion' listing again.
Perhaps it will catch someones eye that can help you with advice.
Cheers
OK, let's see what conditions we have going here. I don't have an idea of the soil conditions. I have no idea if you need a permit for this work. Is there a soil engineer anywhere around that could help with this decision?
You are building your own house and you are concerned about the cost of 16' posts? The digging of them or the sonotube or the concrete?
T&G will not stop rain. Is that a consideration? I use fir T&G flooring here on restoration projects, but I prime all sides and make sure the runoff goes where I want it and PT supports are in place.
You have expeosed ledgers? What material? You have the house sided and you did not put down flashing before the siding went up?
Are you physically building the house? Acting as a GC?
There is a lot of missing information.
Quality repairs for your home.
Aaron the Handyman
Vancouver, Canada
Thanks for the response.
Soil is mostly clay. Work is permitted. I am GC.
Yes, I'm concerned about the cost of 16' wood posts. Would rather get something more durable for the cost - i.e. the idea of pouring concrete. May just end up with sonotubes plus 8' posts.
As for flashing, there is existing aluminum flashing, which I will leave behind bottom ledger - want to replace at top ledger, however, with something more durable, perhaps copper (yes this info was missing - I was in a hurry and already felt like I was going on too long). Am doing work mostly myself. Concrete wall idea may just be wild hare, as it basically seems there's not good way to protect proposed secondary basement from precipitation, even if flooring sloped correctly.
Lots of questions...not enough details!
You could use 8' posts under the platform frame of the porch floor system and then use decorative post & rail from the platform up to the roof & beam assembly.
Is the roof already there as a result of cantilevered trusses? Or is it to be added to the existing structure?
If you use wood posts what are your footings' specs? What width is the porch?
Wood post have to be far less expensive than contracting for formed concrete post. And if you decide to use 16' treated posts.....how do you plan to keep them straight?
The ledger flashing should have been applied first...behind the housewrap, before the siding. By the way....What kind of siding? There are articles in https://www.finehomebuilding.comm/archive...check it out!
Your concrete contractor can quote the set-up on the basement extension .....but as mentioned...T&G planking leaks!!! Always!
Do not pour concrete directly on or around pipes...septic or otherwise...always "sleeve" them.
..................Iron Helix
Thanks for your response. Sorry for not having more details; didn't want to go on too much.
The porch roof is not cantilevered; it will be added on.
The porch width will be eight or nine feet.
It was my understanding that it's best to use one single post from footing/pier all the way to the roof, not have a platform in between a lower nondecorative and upper decorative post - true?
I don't know how to keep a 16' wood post straight - that's why I was going to pour concrete up to floor, either as wall, contracted formed post, or sonotube. Also have mature poplars I could harvest that may be tall enough but am not sure about treating them/how they will stand up.
As for flashing, I did flash it with aluminum (as I was doing siding, and I did cut back into wrap), but I'm considering putting copper or something more durable up at the roofline, leaving the existing aluminum flashing at the floor ledger. The siding is painted white pine.
The reason I'm concerned about a platform between upper and lower posts is water damage at the base of the upper post - I saw whitewashed tree trunks used as porch posts on top of a slate deck lifted up from the deck with a metal spacer, but I don't know the best place to get one of those (in southwestern Virginia). Advice about using poplar tree trunks as posts - need to be painted?
If your floor line ledger is treated material...especially the new stuff (ACQ) the aluminum will be corroded away, as will plain iron and standard galvanized nails and hangers. Triple galvanized at a minimum...stainle$$ is the optimum.
Check it out before you cover it up...or have to tear it all out and do it again!
Metal post bases are available at any building supply...not as common as they were 20 years ago...most of the time we orderd them in for our customers as per the spec on a job for wooden columns/post. They do help keep the post bases from deteriorating as rapidly.
There is no reason you could not use the platform method to do what you wish to do. There are ties and anchors available to keep it all laced together. If you are working alone then this would make your project easier...especially the roof.
How do you plan to marry the porch roof to the existing house roof? What is the exterior wall height from the porch floor position to the house soffit. What is the house's roof pitch?
Roof leaks at the juncture of an added porch and an existing roof are notorious problems. Even worse if the roof pitch changes at the transition. Added pita if you have to cut back up into the existing shingles.
What is the roof post & beam design?
How are your ledgers fastened? DO they meet standards for deck loads?
Might as well make the porch 10'....can't buy 9' t&G treated flooring. Besides an 8' porch can be a wee bit narrow with much more than a porch chair, pair of outstretched legs & a passerby!.....actually 10' is small-medium....consider 12' for more people space if design allows.
Poplar/pine log posts might be in tune with your design, but for logevity see if you could use eastern juniper (aromatic cedar) or osage orange (hedge apple). And once again the 8' post length would be easier to find/cut/& handle than a 16' log waggling in the air. IMHO
.................Iron Helix
The floor ledger is untreated painted. The painted white pine wood siding is almost 100% self harvested from surrounding woods.
The house is 2.5 stories - basically a cape cod w. an extra floor. The roof will connect to the side of the house below the roof, to an upper ledger (not sure if term correct). The roof pitch is 9 2/3/12 (rafters all hand-nailed with collar ties and knee walls - yes I'm doing it the old-fahsioned way: power co. would not bring power to site until progress on house shown thus hand-nailing); the porch roof will be much shallower, depending on whether porch width is 8, 9, or 10 (I know 8 and even 10 is tight - (14 would be great but can't do it), had thought of 9 as a concession for size and not making porch roof pitch too shallow). I was planning on the height of porch posts to be 8'.
Roofing material is 3' wide painted metal panels, as will be the porch roof. I know leakage and porch roof junctures are a notorious problem; that's why I want to make sure my flashing at top is best (why I will pull existing aluminum for copper or stainless or - recommendations?) To clarify my original question about nailing flashing to upper/rafter ledger - now there is aluminum flashing coming from underneath siding to on top of ledger, but it flaps in the wind. Also I'm not sure how soon I'll be able to build the porch so am wondering whether to fasten it to roof ledger until I can.
I haven't settled on post & beam design for the porch.
I'm attracted to t&g porch flooring but seems impractical - may settle on closely spaced white oak planks (as opposed to treated wood).
The reason I'd use poplar posts is I have it standing on my property. Thanks for the other suggestions - how about white oak too? (More of that here than osage orange or eastern juniper). If I did use poplar logs, what is best treatment option?
I agree 8' post length is much better than would 16' - that's why I came up w. the concrete walls scheme in the first place.
Many thanks for your patient replies.
If I understand what you are trying to do, the porch floor would become the roof for the new basement area, in which case you would probably want to build it more like a typical roof deck.
What exactly do you mean a typical roof deck? Do you mean a deck on a roof (I've been on some, but haven't built one). Would the deck be t and g or spaced?
To paraphrase cs.....a deck built on a roof = a roof deck.
You would build a flat/lo slope roof system and cover same with EDPM or AWWA program materials, add padding for sleepers to rest on, and then build a deck on top of the roofing.
Build deck as to have removable sections to alllow for repairs when the roof beneath the deck ldecided to eak! And it will!
In terms of your attached ledger being white pine, untreated....it won't last long where there is trapped moisture....as against a concrete wall or where joist tails and hangers are attached. I would suggest that the ledger be treated, as well as the deck/porch subframe....easy enough to change a bad pine floor board.
Back to your use of tin sheets to cover the porch roof...ask your supplier for a list and diagrahm of accesories that are available for the tin/metal/ag roof.
You should see an Item listed as a sidewall flashing that will do what you wish to do at the wall line. Also add in a foam seal strip to keep blow by to a minimum btween the roof metal and the flashing. The flashing is to be screwed to the netal roofing at the ridges using neopreme gasketed hex drive wood tite screws.
I don't know enough detail about the siding to have a specific suggestion as to the proper counter flashing configuration for the end wall flashing....but you need one...a bead of caulk is not a reliable counter flashing.
As far as a treatment/paint to slow the deterioration of your hand cut porch posts...anything will slow the water penetration, but eventually the water will win and rot will set in. The aluminum post bases will help to dry the bases after precipitatio, but eventually....
Be sure to design a post that readily replacable......you will have to sooner or later.
.................Iron Helix
"What exactly do you mean a typical roof deck? Do you mean a deck on a roof (I've been on some, but haven't built one). Would the deck be t and g or spaced?"
You mentioned wanting to use the new basement space below the porch for something other than drainage. That implies you would like it be dry. Therefore, you would want the equiv of a roof under your decking. Since it is a covered porch, that does take much of the weather load off of the 'roof deck'. You should be able to get away with a very low pitch.