How To Re-use and Strengthen Cardboard Boxes

Why buy new cardboard boxes when you can get them secondhand and strengthen them? We'll show you how in this guide

How Can I Make My Re-used Boxes Stronger?

Cardboard boxes are light, easy to store and recyclable - but making sure that the boxes you use to store and transport your things are actually strong enough for the job is essential. 

Have you ever had the bottom of a box fall apart, scattering things on the floor? So have we. This guide shows you how to strengthen a cardboard box to make sure your boxes can handle the job.

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1. Flatten and store boxes for next time

A stash of strong cardboard boxes is useful to have on hand when you need to move house or store things. Empty the boxes completely, flatten them and store them somewhere dry – moisture will weaken the box so it’s of less use to you when you come to use it.    

2. Choose the right type of box

For a box that will handle a heavy load, you’ll need corrugated cardboard. Corrugated cardboard is a layer of concertina-ed card sandwiched between two layers of paper. Corrugated cardboard boxes are more durable and better able at withstanding shocks and drops.

If you're looking for cardboard boxes of any kind, check out our guide on where to get free cardboard boxes for moving:


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3. Tape up the base

The flaps on the base of a box are its weakest point. Don’t close them just by folding them together. Instead, close the two larger flaps over the small ones, then tape over the join using a strong tape.

Use a packing tape (these are available in a range of strengths and even eco-friendly packing tape) or duct tape, although the latter might lose its stick in extreme temperatures.  

For extra protection and to make sure that all of the flaps are sealed, use the letter H seal method used by moving companies, so-called because the tape on the box looks like a capital letter H.

4. Reinforce any gaps  

Lots of cardboard boxes have parts that are glued together. By reinforcing these, you’ll strengthen the box. Find any gaps, glue them together then weigh down the glued areas for a good stick.Make sure to leave the box for the time specified on the glue you are using. Here’s a good guide on how to do it

Dog In A Cardboard Box

5. Tape over joints and edges

The joints and edges both inside and outside of a box are weak spots but you can strengthen and reinforce them with packing or duct tape. Taping the outside of the box in an X shape will strengthen the sides. You can tape each area several times to reinforce it further. 

6. Strengthen and reinforce the bottom
The bottom of your cardboard box will have to carry most of the weight of whatever you put in it. You can reinforce it by adding another layer of cardboard on top of the flaps at the bottom of the box. 

Measure the inside of the box, cut a piece of cardboard to size and slot it in.


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7. Reinforce the sides

If you need to stack your boxes, reinforce the sides. 
  1. Cut pieces of cardboard to size
  2. Glue them to the inside of your box with a strong glue. 
  3. Weigh down the areas you’re sticking 
  4. Leave the glue to do its magic for as long as the instructions say. 
You can add several layers if you need the box to be extra strong.

8. Double box it  

If all of that measuring, cutting and glueing sounds like a hassle, you can avoid it if you have two boxes of the same size and shape. 

Put one box inside the other and double the box’s carrying power. 

Bubble Wrap In Cardboard Box

9. Use foam for shock absorption

If you’re worried about the contents of your box being damaged by knocks, sandwich a layer of foam between the bottom and/or sides of the box and a layer of cardboard. 

Make sure that the glue you choose will stick foam to cardboard. Allow the glue enough time to dry before using the box. 

10. Strengthen corners with cardboard inserts  

If tape is not going to make your box strong enough, insert cardboard pieces folded into a V-shape the entire length of your box corners. 

Make these out of spare cardboard or use the inside of paper towel rolls – this video shows you how. 

Packing up for a move? Use our moving house checklist to make sure you don’t forget anything.


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11. Layer up laths 

If your box needs to do some seriously heavy lifting, you can strengthen it with laths – thin wooden strips a few millimetres thick and a few inches wide. 

Your cardboard will need to be at least two layers thick and you’ll need a staple gun and staples that can handle wood. 

For maximum support, staple the laths in an X shape at the bottom of the box (staple the laths to the bottom of the box from the inside) and run laths up the inside of the box at the corners (staple from the outside). Here are some helpful pictures to show you how.

12. Protect from the elements

If you’re worried that your box will get wet, you can make it more water-resistant and less likely to tear by coating it in resin, epoxy or wood/paper glue. 

You can paint on more than one coat – leave enough time for each coat to dry before applying another. 

If you’re going to tape the outside of the box, do this first and make sure that the resin, epoxy or glue you use will work on the tape you’ve applied. 

Flat Corrugated Cardboard Boxes

13. Reinforce the top

If you’re going to stack your boxes, reinforce the top in the same way as the bottom and sides by taping a piece of cardboard cut to size to the top of your box once it’s filled. 

We hope this guide helps you extend the life of your cardboard boxes! If you’re on the hunt for a storage space, take a look at the thousands of storage spaces available on Stashbee.

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Updated 13th Apr 2023

Written 27th Feb 2023