Drywall Interiors
Modern construction here in the United States uses <strong>drywall</strong> otherwise known as gypsum board as its primary choice for interior finishes. There are many advantages to drywall, namely the facts that it is non-combustible, easy to install and also repair, and best of all economical.
There are several types of drywall available today. They include fire rated, mold and moisture resistant and even sound deadening products. Most common applications use what is referred to as standard board. You will find that most products in the retail market will have tapered edges for ease of joint finish.
Drywall is commonly available in 4 foot width with length ranging from 8 foot to 16 foot in even foot increments. A popular relatively new drywall product commonly referred to as stretch drywall as it is a wider 54 inch width so 2 sheets fit a 9 foot wall without trimming.
Another recent change in the drywall industry is the availability of lightweight drywall. I have seen this becoming the product of choice in our market for the simple fact that lighter makes it easier to handle.
Fire rated or Type-X drywall is typically available in 5/8 inch thickness and is commonly used wherever a fire rating surface is required. This is most commonly ceiling areas, areas around or containing combustibles like furnace rooms or garage separation walls.
Mold resistant drywall has become the new standard in high moisture areas and has replaced the old product referred to as moisture resistant drywall. Mold resistant drywall is commonly used in basement areas as well as laundry room, around bath tubs, and showers. You get the idea, anywhere moisture is a concern, so is mold. The technology used is basically a paperless surface that will not breed mold spores.
Drywall Installation
When it comes to drywall installation on walls it is common to lay the sheets over horizontally with end butts centered on studs and the horizontal common edge being a tapered joint edge. Another popular option is to stand the drywall sheets vertically cut to fit the ceiling height with only tapered vertical joints located on studs.
It is most common to install drywall with either a phosphate coated course thread drywall screw or a cup head ring shank drywall nail. Common practice is to use 1-1/4 inch fasteners for ½ inch drywall and 1-5/8 inch fasteners for 5/8 inch drywall. Fasteners should be held back 3/8 inch from edges and be placed every 6 to 8 inches apart on walls and 5 to 7 inches apart on ceilings. Be sure to attack fasteners in this pattern along every stud , joist or plate surface.
When finishing drywall you can use the following standard methods. Understand that there are other methods also available.
1. Use a wide drywall taping knife (5 to 6 inch work best) and spread joint compound in the center of the joints, beginning at the top of the wall.
2. Press drywall tape into the recess with your putty knife until the joint compound is forced through the perforations in the tape. (If you use fiberglass tape I suggest using fast drying drywall cement like a speed set product to avoid joint cracking)
3. Cover the taped joint with additional drywall mud, feathering the outer edges.
4. Allow this drywall compound to dry thoroughly, then sand the joint lightly. Now you are ready to add a second layer of drywall compound. You may finally need a third coat but the secret here is to taper each coat out a little further to feather the edge and blend it in.
5. After the final coat is dry it is time for a final drywall sanding.
6. You will blend the over the screw heads as well as any hammer dimples by coating with drywall compound and when dry feathering the edges with sand paper like the joints.
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Everything About Drywall
Monday, March 19th 2012 at 6:48 pm |
I need to replace the roof on a stand-alone screen house located in northern MN. The pitch on the roof is less than 1-12. Would you recommend that I use treated or untreated plywood for this purpose.
Thanks
Monday, March 19th 2012 at 7:13 pm |
The key here is to understand that both treated and untreated plywood are only as good as the glue used. Treated plywood will not rot but the plys will still delaminate if constantly exposed to moisture.
So if your plan is to install this relatively flat roof without some form of rolled roofing or rubber membrane protecting then my advice is to seal all surfaces and edges of the plywood with a good oil based paint prior to installation to seal out the moisture as well as possible.
Even with a protective roofing cover it is still a good idea to seal your exposed plywood surfaces to keep them from absorbing moisture.
Friday, May 18th 2012 at 10:55 am |
I am in the permitting process for a small 20’ by 24’ cabin in Northern Arizona. The building has a 12’x20 loft over the back half. The building is being carried on 4 – 12”x12” piers along each side and 4 down the middle, each resting on 2’ square footing. The question has to do with the bottom outboard rim-joists carrying the back half of the bottom floor, loft area and roof.
The span between the piers is 6’8”. The rim-joists in that area will be carrying 40 lbs live load each per floor and roof and 15lbs dead load each per floor and roof for a total load of 165 lbs per square foot. The rim-joists will be carrying half the load from the outside of the outer piers to the center = 5’ x 165 lbs = or 825 lbs per running foot evenly distributed over the span of the rim joist or 6′ 8″.
The building is scheduled to have either 7/16th or 1/2 inch OSB sheathing installed either across or parallel to the 2×4 @ 16” oc framing. The sheathing will start at the bottom of the outer rim-joist which I calculated to be doubled 2×8 Doug-fir.
If the sheathing is installed horizontally, the break between the panels on the first course would occur over the centerline of the footings, and the sheathing and framing system in my opinion would serve as a box beam or truss. I am willing to install blocking as a top cord at the top of the break between the sheets at 4’ or 8’ depending on the installation, and am willing to nail the sheathing on at some nailing schedule designed to accommodate the load. The top is in compression and the bottom is in tension.
This building is small and will only be used seasonally but the Coconino County Permitting Authority will allow no compensation for the sheathing and originally specified 5 1/8 x 10 glu-lam but now is down to a 3 1/8 x 9” Glue-lam or 4 – 2x12s bolted together to span the 6’8”.
Can someone provide me with the mathematics to demonstrate the load carrying capacity of the wall system including the sheathing?
Thanks,
Bill Cowan
Rimrock, Arizona
Friday, May 18th 2012 at 1:48 pm |
Hello Bill,
Thank you for visiting my site and for the interesting question. First I must clarify that I am not an engineer but I am a designer with over thirty years in this industry.
I am including a scanned image of the header table I would use to size your project and as you will see the design call-out for you situation would be a minimum of 3-2×10’s base on Hem-Fir lumber and a 40# roof live load.
I don’t know that you will have any success finding anyone to define a system rating including the sheeting and even if they did make a recommendation it still comes back to your permitting department’s discretion. Keeping in mind that the person we are talking about is just another person like you and I doing the job they were hired to do and technically they are liable for accepting or disapproval of any deviation from their approved standards.
So I would recommend that you consider taking this chart and visiting with them remembering that you will have much better success bringing a spirit of cooperation with the contact at the county permitting authority.
I hope this information is helpful and thanks again for checking out my site. This site is relatively new and so if you happen to be a Facebook user I would appreciate your liking our site as this seems to be a good way to get the word out that the site is here to help.
Sincerely
Jim Patrick
Home Building Questions