25 Bridge Building Tips

1. Humidity affects the weight of your bridge. Keep your bridge in a closed container with a few grains of rice. or some silica gel packets.

2. Go easy with the glue bottle. As a general rule of thumb, if you can see it than you are using too much.

3. Keep your hands clean! Oils and grease from your skin can ruin your glue joints.

4. Perfect practice makes perfect. The more bridges you build, the better your construction skills will be.

5. Keep your bridge from twisting by using lateral bracing.

6. An L-beam is more efficient than a square, but harder to build.

7. Balsa wood comes in a wide range of densities and stiffness. Weigh each piece that you buy.

8. It is cheaper to buy Balsa in sheets and cut your own wood strips.

9. It’s still true, measure twice and cut once.

10. Keep a log of every bridge you build. Record notes and dimensions; you won’t remember later on.

11. Try to videotape testing your bridge. You may get a clue on what failed first.

12. Always keep safety in mind when using sharp tools. Most mistakes are made when you aren’t paying attention.

13. By cutting a piece in half, you more than double its strength in compression.

14. Good lighting when working will help you perfect those little details.

15. Always test your bridge before taking it to a competition, but leave enough time to build another.

16. Draw out your bridge on graph paper to make sure that it is symmetrical. I prefer the 11″ x 17″ graph paper.

17. Different trusses have different ways of spreading out the load.

18. Wood has about the same strength in tension, no matter how long it is.

19. CA glue is a fairly strong, light, fast-drying glue used by many builders.

20. Balsa wood sands very easily. Be careful not to sand off too much.

21. You can mix wood glue with water to cut down on weight. Doing this also helps the glue to seep into the wood, creating a stronger joint.

22. Remember to close your glue bottle when you are done using it.

23. Basswood will bend easier than Balsa wood. Try steaming or soaking your wood to help it bend.

24. Use Lap joints whenever possible to get the best strength.

25. What you want to look for in glue: drying time, price, weight, and strength.

These bridge building tips will give you a head start when you start designing and building your model bridges. These tips come from my years of experience starting from my time in the Science Olympiad competition and continuing beyond building for fun. Disclaimer: these tips are my own opinion based out of my experience. Other builders might have different views and we might not agree. I encourage you to try things out on your own and decide for yourself what is the best way to build a bridge. Who knows, I could have been wrong about something.

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25 Responses to “25 Bridge Building Tips”

  1. bob - September 10, 2008 at 11:02 am

    i like this, thank you very much. this is so cool

  2. Jenny - October 16, 2009 at 9:40 pm

    THANKS! This was super helpful, I am doing a model bridge for science olmpiad and i hope these tips work.

    • mike - March 20, 2015 at 8:42 pm

      Same here, im going to state this year hopfully win

  3. Harmony - October 19, 2009 at 11:14 am

    hey, that post really helped! im doing research for a secme competition!lol, thanks!

  4. ann - January 8, 2010 at 10:04 am

    what is the best glue to use for making the bridge. I was using crazy glue it doesnt seem to be working.

  5. Michael - May 2, 2010 at 4:46 pm

    Wouldn’t putting water into your glue dilute it therefore making it weaker???

    • yonu - May 20, 2010 at 12:38 pm

      yeah… it will!

    • Garrett Boon - May 21, 2010 at 10:43 am

      No, if it is wood glue (Elmer’s, Titebond) then adding a percentage of water will actually increase the strength of the joint. The water thins the glue, making better able to seep deep in the wood, creating a better joint.

      • bowen zhan - October 15, 2010 at 11:28 am

        you have to dry it first..

  6. Fidel - May 4, 2010 at 1:10 pm

    Any tips when using squared cross section popsicle sticks to avoid uneven beams or elements (because of different cross section dimensions between one stick and another)? And… should I cut sticks ends in angle to exactly fit between other 2 sticks forming an angle?

    • Kayla Barhorst - December 10, 2015 at 9:36 am

      Okay so let me get this straight that this will help me to build a home made bridge?

  7. Fidel - May 23, 2010 at 11:40 am

    OMG I have to finish my bridge before this friday =O im scared XD Will my bridge make it?? :O

    • Kayla Barhorst - December 10, 2015 at 9:37 am

      It will just calm down and take a deep breath and pray for the best

  8. bowen zhan - October 15, 2010 at 11:26 am

    how do you build a suspension?
    I’ve been to the summer camp to learn those stuff but they didn’t told me how to build a suspension??

  9. garrett - December 6, 2010 at 7:44 pm

    i need blueprints and fast! Garrett Boon can you help me obtian them,please.

  10. christopher pepin - May 3, 2011 at 4:17 am

    Random factoid for those interested,when you put a beam in compression the formula for the weight it can hold is P = c * (E*I)/L^2 where P is you load and L is the length. Making a beam half as long actually increases the weight capacity by 4. Similarly cutting it down to a fourth the size increase the weight 16 fold.

    • Raelynn - November 15, 2011 at 9:51 pm

      This was very informative and helped me very much. I am very grateful. 😀

  11. Erik C. - February 14, 2012 at 11:43 am

    I once built a bridge for an Odyssey of the Mind competition, and now I have to build one for an Engineering class. I remember my OM coach drying out the bridge in an oven. She set the structure on a cookie sheet and then sprinkled silica gel on the sheet before baking it. I don’t remember the specifics but would like to try this trick for a better efficiency ratio. Do you know anything about this weight-saving method?

    • Garrett Boon - February 15, 2012 at 7:51 am


      What I have heard is that baking a bridge in an oven has only temporary gain in weight loss. The moisture that is removed by the oven is quickly replaced by the humidity in the air. Also, you have to be careful about the heat level and what glue you are using.

  12. emma - February 27, 2012 at 6:07 pm

    Can testors glue (for metal and wood models) be mixed with water?

  13. xavier zuniga - October 15, 2013 at 3:20 pm

    we are doing this in my class… its so cool! I will wright back what happens soon! Thanks for all of this information!

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