|Volume 6 Issue 3||“Building Confidence”||March 2008|
Welcome to our newsletter. We hope your Spring projects are getting under way, weather permitting, of course.
Here are some of the questions I answered this month:
Hi Dave, I just had a couple quick questions about installing 5" tongue and groove pine on the ceiling of my covered patio. First, since it's outside, should I use galvanized nails? We live in a desert climate in eastern Washington State with relatively low humidity if that makes a difference. Second, I was thinking about applying some type of stain finish and wondered if it would be better to do it prior to installation or if it makes much difference. Also, do you think stain is sufficient to protect the wood or will I need to apply some kind of sealer as well? Best Regards, Mike
Hi Mike and welcome to our site,
Usually, in the interior we use a coated nail for outside work. On the coast we use galvanized nails. One thing nice about the coated nails is that they are smaller gauge so don't split the wood as much as the hot dipped galvanized.
It is a good idea to pre-stain any siding since the wood expands and contracts with temperature changes. If the wood is pre-stained it doesn't show the wood line left without stain during expansion. The second coat is applied after the siding is installed. Since the wood is on a ceiling, it probably would not need a sealer as siding exposed to the weather would. A good oil based stain keeps the wood looking good, especially for a ceiling.
All the best,
Thank you very much Dave – great info. You and your site are a fantastic resource; I just wish I had found it earlier. Mike
Thanks, Mike, don't hesitate to ask a question as the need arises. Dave
Dave, I had written you before asking about the footings of building I want to build. I had asked you about trench footings. At your suggestion, I talked to the building inspector. He said trench footings are allowed in Boone county Missouri. I need the fall to the existing sewer line, so I need to use fill dirt to level the site before digging the trench. I need to build the site up from zero to 12 inches along a 52 foot run. I want to make the site level then dig the trenches. I believe I can use 2 X 6 forms on top of the trench to form the top of footings. What is the best way to place and pack the fill dirt? What should I use to compact the soil. I would imagine building the soil up in layers. Advice will be appreciated.
Yes, build the layers up about 3" to 6". Compact the soil with a plate compactor. These are readily available at rental yards for not too much of a cost. Use a sand and gravel base that compacts nicely. In some areas a pit run is the cheapest if it compacts well. You don't want the trench to cave in when you dig it out. Here's a picture of the compactor:
Better check with your local inspector to see if the grade is 6" or 8" below the top of concrete. In my area it is 8". You may need to use 2x8 or 2x10 forms. Check to see what your floor joists are so you don't need to buy special forms, just use them.
If you need help in designing the forms let me know the width and depth of the trench, etc.
Hope this helps,
Dave, The project will not require anything larger than 2 X 6 so I want to avoid using larger boards for forms if I can. The roof trusses are engineered, the 16' garage door header is engineered because it will support the trusses. The floor will be concrete. I have a second 8' door that will require a 2 x 10 header, but that's not much compared with all the boards required for the forms. The code says that I need 6 inches between the top of the concrete and the soil. I'm thinking it would be less expensive to build the site 2 inches higher with fill, then scrape it away after the footings are poured to get the 6 inches required. What do you think? Forms The footing trench will be 12 inches wide and 40 inches deep. The frost code is 30 inches, but I thought the extra 10 inches would increase stability. Do you think the extra 10 inches adds value? 12 inches wide and 30 inches deep are code minimums. I thought I would rent a mini excavator with a 12 inch bucket to dig the footing trench. What do you think? You are correct, I want to choose the correct fill and pack it well so that it does not cave when dug. I would be interested in help with the concrete form design. I imagine the 2 X 6s set along the edge of the trench as a vertical continuation of the earth wall. I want to build the forms ahead of time so they can be quickly fastened into place. I figure the re bar structure as #4. Verticals 4' on center. 2 horizontals. I plan to construct this in 4 sections bending around the corners ahead of digging the trench. When the trench is dug, I'll place the 4 sections in the trench tying together the 4 splices in the trench. What do you think? With the forms and re bar sections built ahead of time, I want to dig the trench, place the re bar in the trench, set the forms above trench, and pour the footings in two days. I don't want the open trench to be rained on if I can avoid it. I plan on removing the grass before packing the fill. How early can I start spreading and packing the fill? I assume all the frost must be out of the ground, but does the ground need to be good and dry or a specific soil temperature. The inspector told me to plan to purchase 2 times the packed volume of fill. Is that a good rule of thumb? I had two 8" diameter trunk trees close to where the footing trenches will be dug. I had them moved about 1 month ago with a large tree spade. I'm trying to pack the replacement soil as best I can, but I want to anticipate the trench caving in those areas. Do you have advice about compacting these areas? Can you help me plan for a form to bridge the gap where the walls might cave? Those are my questions for now. Thanks for your advice.
You seem to have a good grasp on everything. The frost should definitely be out of the soil before compacting. The low temps should be above freezing. Compact the area first before placing any fill. When the frost comes out of the ground it always makes the ground soft.
I have never done a trench footing like this, but I would suggest you make the last 6" to be a standard 8" wide rather than 12". This gives a bit of tolerance if the trench is not perfectly straight. I can help design the forms for you, just let me know exactly the way you want to go.
If the trench caves in a bit just put in a disposable board along side. I'll draw you a sketch of this and the forms later.
When do you plan to start?
Thanks for the reply. I'm not sure I understand the statement: I would suggest you make the last 6" to be a standard 8" wide rather than 12". I plan to start as soon as the weather is fit. I hope within the next 30 days. Steve
Hope this drawing helps:
I was thinking about your comment regarding the 2 X 6 form vs. 2 X 8 or 2 X 10 to add additional distance between the plate and the ground. Can the forms be built above grade allowing a small amount of concrete to ooze out the bottom. As in this drawing:
When pouring concrete like this the concrete has a low slump which means not too much water is added. The mix is stiff so a 1 1/2" gap in the bottom of the form won't cause a problem. Here is a drawing of a suggested way of building the forms so they will be supported over the trench. Also, the anchor bolts could be held in a hole in the cleat or just embedded in the wet concrete after finishing the top. The brace should be about 4' long to get away from the open trench. You can adjust the forms up a bit to keep them level with a wedge on the 2x4 block and adjust the form to a straight line by nailing the brace to the stake.
Dave, How about estmating the volume of fill. I can figure volume, but what about the pack factor? The building inspector said figure 2 times the volume required. Does that sound about right? The volume to fill figures about 37 cu yds. Given the 2 X, that would make 74 cu yds to order. What's a large dump truck hold, about 10 yds. I guess I can ask that of the company I'm purchasing it. The ground is still squishy under foot. Probably too early to start. Maybe another week depending on the weather.
I think your estimate for fill to level the site is way too high. You say the building is 32x52 with a slope of 12" to 0 in 52 ft. I'm figuring you would make the width about 2'. If I were you, I wouldn't allow any purchased fill for under the slab. You could use the fill from the trench excavation for this purpose.
So for each long side the fill is 52 x .5 x2' wide =104 cu. ft for both long sides. Add the lower 32' side 32 x 1 x2 =64 plus 104 = 168 cu. ft or 6.22 cu. yards. 168/27 = 6.22
I would say the inspector is a little high with his estimate. I would go with 20 to 25% increase in fill for compaction. 6.22 yards x 1.25 = 7.77 or a nominal 8 cu. yards.
Dave, I figured 8' instead of 2'. I figured 8' to form a wider base so the machine digging the trench would be on on the level surface. Do you think 2' will work? I was consider using a mini excavator to dig the trench. Would a traditional backhoe have enough clearance to straddle the build up of 12" deep and 2' wide of dirt? Maybe you are considering digging the trench in a way that the 2' will work differently than I'm thinking. Thanks, Steve
All I'm thinking about is the fill required to pour the concrete, hold the forms in place level and having to do too much work. Even the mini excavator should straddle the 2'. as long as the clearance is 12". Remember the finish grade line is 6" below top of concrete. This means you need to replace the 2' or 8' wide fill with topsoil or whatever the finish is around this building, later.
Have you considered doing a slab on grade, a monolythic pour? That is pouring the slab and perimeter footings together.
Dave, I thought about a monolythic pour. However, discounted it because of all the prep work and labor required to do it all at once. I will be putting drain pipes and water lines in the floor. I'm hoping to do it a section at a time. Your comments have me questioning the idea of leveling the site with fill first. What do you think about not putting in the fill first, but using forms on top of the sloping surface trench to make the top of the footings level? The form width increase from 6" tall at one end of the 52' run to 18" tall at the other end of the 52. Similar change on the other 3 sides of the footing rectangle. By adding the fill at the end I could use the dirt that is dug from the trench and only purchase what I was short. Also, I could fill with topsoil on the outside to the required grade. How would such a form be built? Could particle board be placed so that 2" would extend below the surface along the wall of the trench? This could help hold the spread at the bottom. The attachment is my basic idea. You may have a better one. Please recommend thickness of particle board and other lumber to build the form I have included an attachment to help with my discription.
Now I like this scenario. I agree that filling the site to get the forms level is redundant. Your attached drawing makes good sense. When we do forms we always use 3/4" plywood. You could get away with 5/8" standard sheathing grade for low forms like this, framed with 2x4, etc. whatever you are framing with. A tip - if you want some cheap 2x4s for the shorts for braces and stakes, purchase 6 footers from builders supply. They won't sell 6's at big box stores.
Another thing I would like to mention: the slab should come up to the wall rather than sit on top of it. I think you mentioned pouring the slab on top of the wall a while back. Two reasons, first is that the slab is sitting entirely on compacted fill to settle evenly; the second is the exterior wall will be finished better without a joint of the slab showing on the outside. We just don't do it that way, at least in my experience. For a garage the slab should be sloped slightly to the door, 3" in 20 ft. Any water off the vehicle will run against the concrete wall this way rather than having the slab flush with the bottom plate of the wall, running into it.
Hi Dave.... I had a question.... the other day I had a guy cut me some bottom cripples for under the rough sill... and the superintendent insisted in a bit of attitude :) that they are not called cripples! they are jacks... I told him I was educated that on any common stud that was cut short for under a rough sill or over a header was a bottom cripple or top cripple.. and jacks/trimmers were the studs that held up the header… My question is.. What is the correct term for it?
Theoretically, you are absolutely correct. Practically, I learned that the cripples are the same as your jack studs, supporting the header and the others were called window or header studs. The studs under the window are definitely not called jacks, they are cripples or just window studs. Jacks are the studs supporting the header, nailed against the king stud, full length.
Interesting also is the jack rafters in a roof are also referred to as cripple rafters. Go figure!
What is important is that the superintendent is still the boss and he can call them anything his little heart desires.
Not too much going on this month. The weather hasn't been too good to us, especially since Spring is supposed to be here now. On March 28th we had a dump of snow measuring about 5". Did somebody mention Global Warming?
I hope our website gives you the confidence to do the work yourself.
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