Flashing Deck Ledgers

hello and welcome to flashing deck Ledger's so what's on deck for this course first we'll talk about required flashing locations for deck Ledger's flashing materials flashing methods and the expected flashing performance let's jump right into the first code requirement it tells us we're exterior porches decks or stairs attached to a wall or floor assembly of wood frame construction flashings required so here we see porches decks or stairs in this example a set of stairs was directly attached to the side wall before the siding was installed and they messed up and should have put flashing in this location though I would just recommend not attaching stairs to a house like this but it can be done and it must be flashed let's look at the other part of this requirement its when the connection is made to wood frame construction so what about this picture in this picture we've eliminated the connection to wood frame construction and the deck is fastened to a concrete foundation this would not require flashing according to that section let's look at another section here it talks about flashing directly approved corrosion-resistant flashing shall be installed shingle flat shingle fashion in a manner to prevent entry of water into the wall cavity the flashing shall extend to the surface of the exterior wall finish let's break this down first this is the requirement for the flashing material this is related to the manner of installation this is a statement about what performance is expected from the flashing and this is another statement about how its installed and this is really all the guidance that the IRC provides for flashing a deck ledger so let's look at this a little deeper we'll start with corrosion-resistant the requirement of the actual flashing material itself this is defined by the IRC as the ability of a material to withstand deterioration of its surface or its properties when exposed to its environment one of one type of deterioration would be rust and that's simply the mixture of iron water oxygen and time that's handled by the use of galvanized steel or materials that will not rust like non iron materials the more common one that we have to deal with is the deterioration that occurs when dissimilar metals contact each other they pass their electrons from one to the other when water passes across them this weekend's the metals if we look at this chart this is a nanotech index of various metals this is it this is a chemical chart related to the chemical reaction of various materials together there's an index at the corner and at the top we have the most the most cathodic metals and at the bottom of the most a notok metals the further apart that metals are on this chart the more dissimilar they are and the more readily electrons pass between them and deterioration will occur so let's look at some common ones used for flashing first we've got a problem we use a lot of pressure treated material out there the lumber the ledger and it's usually treated with copper this is what causes a dissimilar reaction between various flashing materials next down on the list we have stainless steel these are pretty close together so we don't get a lot of corrosion between them further down we have aluminum and even further away from copper is hot dip zinc plated galvanized steel now this is curious because we're told to use hot dip galvanized steel when we're dealing with copper material copper impregnated treated material but when we look at this chemical chart it's actually the most reactive with the copper well there's a reason for that when the copper is in contact with the galvanized steel the zinc coating is the most corrosive and will thus corrode first when zinc coating corrodes it provides a protective shield to the structural steel behind so in fact the least corrosive product to use is the one covered in the most corrosive metal it's kind of interesting let's look at some examples there's ways to use galvanized steel flashing stainless steel flashing aluminum flashing copper flashing you could use vinyl flashing so there's no metal involved at all or you could use a self adhering type of flashing and self adhering flashing is directly discussed in the Code section about flashing by stating in it it must be compliant to aam a seven-eleven that is a standard published by the American architectural Manufacturers Association so when purchasing a self adhering flashing you just want to make sure the products been tested and is in accordance with this standard so now let's talk about the flashing performance that's expected by the code it told us it has to be applied shingle fashion and to the surface of the wall finish it must extend to the surface and it just simply says it must prevent the entry of water that's it this is what the flashings got to do to be code compliant so let's talk about shingle fashion and what that means this means gravity is going to shed water onto the surface of the material below imagine shingles on a roof let's look at an example here's a roof and here's how the shingles would be installed from the bottom working up with each shingle going on top of the one below this allows water to start from the top and as it drains down it's always staying on the surface of the shingle below let's get a little abstract though since we're not dealing with shingles and we're dealing with flashing and let's imagine these four shapes right here and we're going to get rid of the roof now how are we going to get water from the top up here down to the bottom left without it falling in between the cracks and falling within the building cavity we're going to install flashing shingle fashion we're going to start from the bottom working our way up and making sure each piece of flashing laps over the next now when the water is dropped at the top just like it did on the shingles the water is always staying on the surface of the building and down to the ground that's it so how are you going to do this and how will you install or approve flashing four decks let's look at some design sources that might provide a little guidance where the code has now ended if we go to this document this is from the EPA and this is from their indoor air and moisture control guidance EPA that seems like a reasonable source of information so let's see what they show they require the l-shaped painted or galvanized metal flashing here just like the code requires they show the building paper behind again that would already be required by the code to cover the wall sheathing they add in a self adhering membrane behind the ledger this is likely to heal the hole penetrated by the lag bolt or the bolt going through or the lag screw the self adhering material will heal and stick around that fastener and then at the bottom they have another piece of drip edge as just probably safe measure this would not be required by the code unless the siting pretreated out further than the Leger above they have another detail that doesn't include metal this one again has the building paper behind that should already be in place and the self adhering membrane is now placed over the face of the ledger as opposed to behind it this eliminates the need for the metal flashing and again they show the drip edge flashing at the bottom one thing I don't like about the guidance from the EPA is in this side detail where they show the flashing cut at every one of the joist locations with the flashing extending out flat there's no drip edge at the bottom to break the surface tension of the water and there is possibility for the water to roll underneath the flashing and behind the ledger it also provides quite a pocket of debris and deck builders will certainly understand what I mean by that that's this situation where a pocket of debris often gets created at the house and deck portion it's not debris-filled at first but within short order of an owner living there leaves dirt dog hair fills up that debris ultimately bringing the earth right to the structure this would be best to be avoided but that's just good advice the building science corporation is a great source for anything related to building science moisture and thermal requirements testing research advice building science comm is a website you can spend hours on they have an article that does provide some great details and their guidance for properly flashing a deck and here they've done a good job no notching of the flashing they show the LED the flashing going behind the joist I think this is a better detail finally the detail we've seen before from the adhered masonry veneer manufacturers association here provides a little guidance in a little a little detail for how to flash the deck ledger at the adhered veneer so let's wrap up this one with the intent and purpose and it's really simple when it comes to flashing flashing must not corrode or else it's not going to do its job it's not going to work right flashing must be installed like shingles so gravity can do its job to shed the water to the building surface flashing relies on physics for it to work properly and then flashing must do its job and keep the water out of the building cavity this is what the code is requiring and this is what everyone should be striving for my name is Glenn Mathewson and I thank you for learning with me today

Channel: Glenn Mathewson

Views: 245,822

Rating: 4.6636481 out of 5

Keywords: Flashing, IRC, International Residential Code, ICC, International Code Council, Decks, Decking, training, code

Id: eCGOFF8Plys

Length: 10min 57sec (657 seconds)

Published: Mon Mar 10 2014