Sheathing and strapping is probably a term you have heard mentioned before if you have been following the tiny house movement for some time. But don’t worry if you haven’t because in this article we are going to take a deep dive into what these two are all about and how you can best use them on your own tiny house build. Both sheathing and strapping of a timber tiny house frame are designed to increase the structural strength of the structure. This is particularly important in the case of a tiny house as it is subject to a lot more movement and additional forces such as wind and vibrations compared to a conventional house.
Sheathing & Bracing your tiny house is not a step that all tiny house builders take so it is not essential but in this article I’m going to talk about why we might want to think about it and how to do get the job done with some step by step instructions.
What Is Sheathing & Strapping?
Sheathing is a process whereby we apply sheets of structural timber such as plywood to the outside of the timber wall and roof framing to add an additional layer of strength and bracing and also to create an additional air and water barrier for increased insulation. Bracing on the other hand is where use galvanised steel strapping that we tension to create extra structural support.
Why Should I Sheath My Tiny House?
There are a couple of main reasons why you might want to consider sheathing your tiny house. Here’s a couple:
- It increases the structural integrity of the whole structure.
- It adds another layer of weather protection to your tiny house.
Why Should I Strap My Tiny House?
- It also increases the structural integrity of the whole structure.
- It is quick and easy and gives you the added peace of mind.
The structural integrity of your completed tiny house is of course a very important factor to consider as this may be your home for many years and the last thing we want after spending countless hours and a fair bit of cash is our beloved home falling apart. So it pays to make sure we invest the money upfront in the elements of our build which will result in a quality, long lasting product. Structural design is one of these.
The other point to consider is the additional layer of weather protection that you will receive by installing it. It will not only keep our more of the heat in summer but will also help to keep in the warmth in winter. Any added insulation is always a bonus down the track especially with Australia’s hot summers.
What Are The Down Sides To Sheathing & Strapping My Tiny House?
The only two down sides to sheathing your tiny house are the extra cost and the time it takes to install it all. In Australia it will cost you around $600 to sheath a 7.2 metre long tiny house if you use a product called OSB which stands for Orientated Strand Board. It is a man-made structural product which is only 6mm thick but very strong and perfectly suited to bracing applications. The other option is to use 6mm structural plywood which works out a little more expensive.
The down sides to strapping your tiny house are very similar to sheathing but it does cost a lot less and takes a lot less time to install. When building our first tiny house prototype we chose to both strap and sheath to have the extra piece of mind that we had made our home as strong as it could possibly be out of timber. I feel the extra cost was worth it as our home has since towed fantastically and we have had no cracks appear on the inside on any of our walls or ceiling which was one of our major worries as we have beautiful smooth white walls! Not bad considering our home has already travelling over 300km so far.
How To Strap Your Tiny House
Strapping your tiny house is another layer of bracing which is really not essential but it is something that is often recommended by structural engineers in the case of tiny houses as it does provide extra support against all of the movement and forces that a tiny house is subject to.
To strap your tiny house you will first need to make sure that all of your framing is complete. If you are happy that everything is 100% complete then it is time to talk materials for the job. In order to carry out this job you will need a few things first. Before going and buying the items listed below have a good look at your drawings and calculate how much of each item you think you will need as the numbers below are purely a rough guide only.
Your shopping list should look something like this:
– The same nails or screws that were used to construct the framing
– A roll of galvanised strapping (available from most hardware stores) – approximately 100 metres for a 7.2 metre long tiny (this will give you enough for all of the walls and the roof)
– At least 20 tensioners (these come in packets with a few per pack)
– Tin snips
The whole idea of strapping is to create a series of crosses along all of the exterior sides of your tiny house, including the roof. Each cross generally overlaps the last very slightly as well. Like the images below.
Now to get into the work:
- Start by taking your new roll of galvanised strapping and finding the end. Take the end and place it against your framing in a corner. You can start at the top or bottom, front or back. It will work the same.
- Fix the end to the framing using your nails or screws.
- Run out the strapping to the opposite corner of that wall. So if you started at the bottom and at the front then you will run it up to the back and fix it at the top of your wall frame. If your strap at any point crosses over where a window or door is then you will need to run shorter pieces so that they start and finish before windows and door openings. Like the image above!
- Now we have a strap going in one direction we need to create our cross by installing one perpendicular to it. Again, if you run into a door or window opening then simply terminate the strap before the door or window and then start a brand new cross of strapping after the window or door
- Now repeat this process for each side making sure to overlap each cross slightly and making sure to put a cross in between each door and window.
- Once all of the walls are strapped then we need to carry out the same process on the roof. On an average tiny house 3 crosses along the length of the roof is usually sufficient but check with your drawings to see if they state otherwise. If your roof is flat/skillion then you will have 3 overlapping crosses but if you have a pitched roof then you will need to run 3 crosses down each side of the ridge.
- Once all of your strapping is installed it is time to tension it up!
- To do this grab one of the tensioners that we bought earlier and locate a position about half way along one of your pieces of strapping. Orientate the tensioner facing into the wall cavity so that it is flush on the outside for easy installation of our sheathing.
- Now slowly tighten the wing nut until it is finger tight.
- Repeat step 9 for each strap.
- Now go all over the house and give each tensioner a good tighten up. Go as tight as you can using your fingers.
Congratulations! You have just successfully strapped your tiny house and made it significantly stronger which should make sure that it stands strong for many years to come!
How To Sheath Your Tiny House
Now we have our frame completed and strapping done it is time to start sealing up the structure. This starts by sheathing the entire structure using a structural form of panel. There are two main choices of material for this job:
- 6mm Structural Plywood; or
- 6mm Oriented Strand Board (OSB)
Both materials will get the job done but OSB is quite a bit cheaper so the preferred option for most tiny housers. Once we have chosen a material it is simply a matter of calculating how many panels and nails/screws we will need and then making a trip to the local hardware store. Refer to your local hardware stores website for info on the product that you are going to use for this when calculating how many sheets your will need.
Keep in mind that not all materials come in exactly the same sheet sizes. For example, OSB comes in various sizes but the largest being a sheet of 2745 x 1200. Plywood also comes in various sizes but the largest being 2440 x 1220. The difference in length of 305mm between the two doesn’t sound like a lot but it can save you from buying half a dozen sheets which adds up pretty quickly at more than $20 per sheet.
Have a look at the height of your walls and see how this is going to work with either of the sheets. In tiny house builds I have been involved with I have seen walls at around 3 metres high where we used the 2745 x 1200 sheets of OSB standing tall and stacked side by side. We then cut thin strips to fill in the remaining 255mm gap along the tops of the walls. By working out how you will stack them it will help you to calculate how many you will need. Below is sheathing using OSB sheets at 2745 x 1200.
Once you are happy with what you will need make a trip to the hardware store and grap your materials and then we can get stuck into the work! To make life easy grab yourself a buddy to complete this job as the size of the sheets makes it very awkward to do by yourself and not much fun.
- Starting at the front of your tiny house place your first sheet against the wall and align it at the bottom with the top of the trailer frame and also make sure that the side edge is flush with your framing. When you are happy nail or screw it in place using a couple of fixings.
- Then stand back and double check to make sure it is aligned. If it is then install the remaining fixings at approximately 600mm centres. Refer to your drawing to see if fixing specifications differ to this figure. If they do follow your drawings.
- Now butt up the next sheet to your first and repeat the same process as the first sheet.
- Continue with this process for the whole house.
- When you come to a window or door opening simply install the sheet as per normal over the opening. We will cut this out after installing the sheet!
- Now go inside with a drill and a large drill bit around 12mm and drill a hole in each corner of your window/door opening that you have just covered over. This will enable you to mark lines on the outside and cut it out.
- Now move back outside and using a spirit level or other straight edge mark lines between each hole that you just drilled but along the outside edge of each hole to make sure that the opening remains the same size as the opening in the framing behind it.
- Using a jigsaw, circular saw or reciprocating saw cut out the sheathing along your lines.
- Repeat this process for each sheet and opening in the tiny house.
If you are unsure whether you need sheathing or bracing then get in touch with our talented design team! Our team of architects and structural engineers will be happy to help. We can give suggestions for your unique scenario or work with you to create building plans that incorporate all of these elements so you don’t even have to think about it. Send us an email and we will get back to you with some more information. Please also leave a comment below and let me know what you thought. 🙂
P.S If you just skimmed the entire post (like I would) here’s a summary of what’s covered in the blog post above. You will learn:
– What is sheathing.
– Why you should consider sheathing your tiny house.
– What is strapping.
– Why you should consider strapping your tiny house.
– How to install sheathing and strapping on your tiny house with step by step instructions.