Efficiency by Design - Foundation

The foundation of your house is perhaps the most important feature. Get it right and the whole house can last for a hundred years or more. Get it wrong and you'll be plagued with callbacks.

We at Istockhouseplans understand this concern. However we also like to weigh the other side of the balance with efficiency by design and optimizing your materials. We did the research and found out how to keep your house strong and save money at the same time.

Unbuckling Your Walls

Pop Quiz:

Why does wall sheathing buckle?

If you answered something like studs at 24" o.c., I'm sorry to disappoint you.  The most common cause of wall sheathing buckling is because it wasn't properly gapped.  We've hounded on this before.  But now the APA has developed a mobile tool that will help educate builders on some of the most common building issues.

See this and many more tips at the APA website.  Tambien en español!

• Prevent Buckling with Proper Spacing includes spacing recommendations for APA Rated Sheathing, APA Rated Sturd-I-Floor®, and APA 303 Siding. (Form M300, now available in Spanish)
• Construct a Solid, Squeak-Free Floor System describes how to prevent floor complaints and callbacks with proper floor sheathing installation. (Form Q300, now available in Spanish)
• Minimize Nail Pops describes how to reduce nail pops through recommended fastener selection and installation. (Form S300, now available in Spanish)
• Storage and Handling of APA Trademarked Panels provides guidelines to help protect panels from damage in storage, during shipment, and on the job site. (Form U450)
• APA Panels for Soffit Applications provides information on recommended panels and spans for open and closed soffits. (Form N330)
• Finishing APA Rated Siding describes recommended finishes and application recommendations for APA Rated Siding. (Form Q350)
• Proper Storage and Handling of Glulam Beams provides recommendations for storage and handling of glulam beams. (Form R540)
• Minimize Glulam Checking Through Proper Storage and Handling provides tips for preventing glulam checking. (Form F455)
• Proper Installation of APA Rated Sheathing for Roof Applications provides step-by-step instructions for roof sheathing installation. (Form N335)
• Proper Selection and Installation of APA Plywood Underlayment includes information on selection, handling, installation and fastening APA Underlayment panels. (Form R340)

Accessing Your Nether Regions

If you build on a crawl space type of foundation then you're going to be required to provide access to that space for future maintenance and dead opposum removal.  Most crawl spaces are required to have a minimum clearance of 18" from grade to the bottom of the framing members.  This is not exactly a pleasant distance to crawl around in but it is at least workable.

What's in your crawl space?  Well not much.  But there is access to plumbing, mechanical (if you don't care about energy efficiency), and some electrical.  There's also dirt, dust, spiders and possibly dead animals.  Maybe there's a drain down there.  It's possible to go years and years without ever having to go down there.  But at some point a visit may be required.

Let's say your waste drain springs a leak.  The waste drain doesn't exactly have crystal clear water in it.  This will require a technician to crawl down into the space with tools and equipment to fix the problem and remove any extras that shouldn't be under your house.  They likely will be up and down several times.  So where is the most likely spot for the crawl access to be?

Believe it or not we often see other designers and architects place this crucial portal in the master bedroom closet.

Really?  Can you see the disgust on our faces?

Not only that but apparently this practice is so ingrained in some designers (and builders even) that they will place the access here regardless of convenience.  If the carpeted master closet is in the far corner of the house this means that dirty nasty crawl space detritus will be making it's way through most of the house starting with your wife's blouses.

We at Istockhouseplans believe that there is a better option.  Our first choice is to place the access in a hall closet preferably where the floor is hardwood.  However an even better choice would be to place the access outside of the house completely.  In some parts of the country this is more common than others.  Placing the crawl access on the outside of the foundation has several advantages:

• Dirty crawl space objects will never enter your house
• The repairman won't have to worry about your wife's clean white laundry
• Most important, the crawl space hatch can't leak warm air out of your house

Of course energy efficiency is important to us.  Based on common practice we often place the crawl space access inside the house in the most convenient spot.  However we thoroughly recommend that it be placed on an outside foundation wall.  If you would like some assistance with details or placement, please feel free to contact us or sound off in the comments below.

Lumber Sizes

Ever notice that a 2x4 isn't really 2"x4"?  What's with that?   Fact is that the piece of wood started at 2"x4" but is called "rough sawn", that is it has unfinished faces.  The stick is then sent through a planer to smooth the faces and reduce serious splinter casualties.  About 1/4" is shaved off of each of the four faces resulting in a lesser dimension than you would expect.  Besides, who would want to say "one-and-a-half by three-and-a-half"?  Mind the twist at 2x8 and beyond...

Now pay attention as we mention dimension convention:

1x:

• 1x2 = .75" x 1.5"
• 1x3 = .75" x 2.5"
• 1x4 = .75" x 3.5"
• 1x6 = .75" x 5.5"
• 1x8 = .75" x 7.5"
• 1x10 = .75" x 9.5"
• 1x12 = .75" x 11.5"

(5/4 material is similar but is 1" thick)

2x:

• 2x2 = 1.5" x 1.5"
• 2x3 = 1.5" x 2.5"
• 2x4 = 1.5" x 3.5"
• 2x6 = 1.5" x 5.5"
• 2x8 = 1.5" x 7.25"
• 2x10 = 1.5" x 9.25"
• 2x12 = 1.5" x 11.25"
• 2x14 = 1.5" x 13.25" 

3x: (for those odd structural plates that engineers like to call out)

• 3x4 = 2.5" x 3.5"
• 3x6 = 2.5" x 5.5"

4x:

• 4x4 = 3.5" x 3.5"
• 4x6 = 3.5" x 5.5"
• 4x8 = 3.5" x 7.25"
• 4x10 = 3.5" x 9.25"
• 4x12 = 3.5" x 11.25"
• 4x14 = 3.5" x 13.25"

6x and beyond follows typical pattern as above.

And while we're at it, how about some typical engineered wood sizes.

I-joists are created by standing a piece of OSB or plywood upright and capping it with a 2x flange.  The result looks like a capital serif 'I' hence the name.

I-joist flange widths (varies by manufacturer):

• 1-3/4"
• 2"
• 2-5/16"
• 3-1/2"

I-joist heights (total height):

• 9-1/2"
• 11-7/8"
• 14"
• 16"
• 18"
• 20"
• 22"
• 24"

Laminated Veneer Lumber (LVL) beams are created by gluing several sheets of 7/8" thick plywood together.  Installation is by standing them on edge so that the profile looks similar to |||

LVL widths:

• 1-3/4" (2 layers)
• 2-5/8" (3 layers)
• 3-1/2" (4 layers)
• 5-1/4" (6 layers)
• 7" (8 layers)

LVL heights:

• Any height possible though generally intended to match I-joist material.  Can match dimensional as well.

Glu-lam beams are created by gluing and compressing several layers of post milled dimensional lumber together.  The whole beam is then planed again to create an even surface.  For this reason, glu-lam beams are slightly narrower than dimensional lumber.  *The industry has recently changed to also offer Gle-lams in full 5-1/2" widths as well.  Heights are always in multiples of 1-1/2" due to the size of the plies.  *The industry has recently changed to offer heights that are consistent with solid sawn and engineered lumber as well.  Due to general engineering practice the height should always exceed the width though rare exceptions always exist.

Glu-lam widths:

• 3-1/8"
• 3-1/2"
• 5-1/8"
• 5-1/2"
• 6-3/4"
• 7-1/4"
• 8-3/4"
• 9-1/4"
• 10-3/4"

Glu-lam heights:

• 6"
• 7.5"
• 9"
• 9.5"
• 10.5"
• 11.875"
• 12"
• 13.5"
• 14"
• 15"
• 16.5"
• 18"
• 19.5"
• 21"
• 22.5"
• 24"

Glu-lams can be used as posts as well.  A 3-1/8"x6" glu-lam post is sturdier than a 4"x6".

Lengthy Topic

Today's little bonus post is brought to you by the American Wood Council and their span calculator at
http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

Don't get to excited, this is not a full structural calculator.  It is, however, a great alternative to checking span tables and they have an iPhone version, handy for field specification.  Mind the deflection.

Happy designing,

Istockhouseplans

Radiant Floor Heat

It was a year ago that we promoted the Warmboard floor system as our choice of heating in homes. We have gotten comments about how expensive that floor system can be. Correct, materials and labor do make it an expensive alternative. Consider that you are removing a $4000-$5000 furnace and ductwork system. Also consider that the floor panels themselves act as the structural floor sheathing. For a 2000sf house you are saving another $1000 by not buying a couple loads of 3/4" T&G plywood. You will probably have to install a second water heater, or a larger water heater, as well as a manifold to handle your different zones.

Also consider this: If your home needs a 60,000 BTU furnace, would you install a 100,000 BTU just to be safe? No! Never! This is poor use of resources and your money. Likewise, would you install a larger radiant floor system than you need? Why? Radiant hydronic floor heat generates about 18-25 BTU/sf of floor. If your home needs 40,000 BTU to stay warm, then you would need to lay 2200sf of 18 BTU/sf system.

But many homes of 2200sf in size only need 30,000 BTU of heat (average NW home). If they are built well, air sealed well, and insulated better, that can be reduced to 20,000 BTU or less. Now do the math. You need 20,000 BTU and your system is 20 BTU/sf. Now you only need 1000sf of panels. This is less than half the floor area. Would you still lay the whole floor, just because? Why? This is akin to doubling your furnace size. Instead, save your money and lay the radiant system only where you need it. Do you need it in bedroom and linen closets? Probably not. Pantry? No. Kitchen? Probably not. The appliances in there create enough residual heat, unless you spend a lot of time cooking barefoot and want warm toes. Hallways and the laundry room could avoid it as well. Bathrooms don't need it under the fixtures. This could remove about 400sf. You could remove more by avoiding areas where furniture would permanently sit.

Since the panels are 4x8x1-1/8", they will fit seamlessly with standard 1-1/8" panels. In our previous example, we could cover half the floor with standard sheathing. Another consideration? With 1-1/8" floor sheathing, your floor joists could span 24" o.c. thereby saving you on framing materials.

And savings is what istockhouseplans is all about.

Advanced Framing Techniques, Floor Joists

Dr. Istockhouseplans continues his thoughts on 24" o.c. framing, floor joist style.

"Dr., why would I space my floor joists at 24" o.c.? Won't the floor bounce more?"

Floor bounce is based on several factors, not just spacing of the joists. Your span is the first factor. Obviously a 16' span will have more bounce than a 12' span. Second is the spacing of the joists. You have voiced your concern about 24" o.c. spacing versus the more conventional 16" o.c. spacing. Third factor is joist size. 2x12 joists will have less bounce over the same span than 2x10 joists will. Fourth is the subfloor material which makes a difference as well. A 1-1/8" thick subfloor feels less bouncy than 3/4" pwd. Tongue and groove pwd helps. Finally, how you attach the floor to the joists impacts the feel of the floor. Nails have less resistance than gluing and screwing the plywood down. By gluing and screwing you actually create one cohesive floor system that moves together.

So why don't we answer your question thusly: no. More accurately, we need to know what else you intend to do with the floor. Are you using 2x12 joists? You should be able to get a 14' span without a problem. Gluing and screwing the plywood may not increase your span-ability but it will make your floor feel stiffer. If this is a second floor then the gypsum board that you apply to the ceiling on the first floor will also help stiffen the joists.

The type of joist you use will have the biggest impact on how you can design the house. There is solid sawn (i.e. 2x12) engineered (I-joists) and open-web floor trusses. Of the three the open-web floor trusses give you the greatest span. They cost more, but the big advantage is that your subcontractors don't need to drill holes through every joist. The open webs facilitate easier running of wiring, piping, and even duct-work thereby saving you money in labor. You also may be able to span up to 20' with a 12" tall member. I-joists are also able to span slightly farther than solid-sawn and also come with knockouts for utilities.

Why would you want to go to 24" o.c. spacing? On the first floor over a foundation the concept is the same as studs. With further spacing of joists there is more room for insulation and less thermal bridging to an unfinished basement or crawl space. You also use less lumber. For the space between a first and second floor there may not be a huge advantage except using less lumber. However I highly recommend using the open-web floor trusses between floors so that ductwork can be run any direction. By using these (@24" o.c.) you can span up to 20' or more thereby reducing the need for bearing walls. It really is a beautiful thing.

Istockhouseplans is proud to present you with a load of plans with details that will facilitate green building. Feel free to browse our catalog and contact us with any questions.