Choosing Between Fiberglass Cloth and Chopped Strand Mat (fiberglass mat)

Do you have a project in mind but have no idea where to start?  Let us help you.  One of the first things you will want to do is decide what kind of fiberglass you want to use.  Do you need to build up thickness fast?  Are you concerned about strength? Do you have tight corners you are working with?  Let us break things down a bit to help you decide if fiberglass cloth is right for your project or if you are needing chopped strand mat. Keep in mind that you can actually use both together to achieve your desired outcome.

Here is an overview –


(Plain weave fiberglass cloth)

Fiberglass Cloth is a woven fabric. Plain, 4 harness satin and 8 harness satin are the weave styles we carry. The 5.6, 6, 7.5 and 10 ounce plain weave fabrics are the most commonly used. In this simple plain weave pattern, warp and fill yarns are interlaced over and under each other in alternating fashion. The plain weave is the easiest to handle since it does not unravel as much as the other weaves when cut.


In the four-harness satin weave pattern there is a three by one interfacing where a filling yarn floats over three warp yarns and under one.


The eight harness satin is similar to the four harness satin except that one filling yarn floats over seven warp yarns and under one.

The satin weaves are slightly stronger and more pliable than the plain weave and are easier to conform to curved surfaces. They are more difficult to handle than the plain weave, though.

Use fiberglass cloth when you are looking to create a strong, light weight product.

fiberglass mat

Chopped Strand Mat (also known as fiberglass mat) has short strands of fibers held together with a resin binder. The fibers are randomly oriented. Mat is only compatible with polyester and vinyl ester resin. When resin is added to the mat, the binder dissolves and the fibers can be moved around. It is easier to conform mat to tight curves and corners than it is with weaved fabric.

The reason chopped strand mat is not compatible with epoxy resin is because the binder holding the fibers together needs styrene to properly dissolve.  Polyester and vinyl ester resins have styrene in them. (There are some places that sell chopped strand mat that is compatible with epoxy but it is hard to come by and much more expensive).

Chopped strand mat is the least expensive fiberglass and is often used in mold construction or projects where thickness is needed. Mat is often used as the first layer (before the gelcoat) in a laminate to prevent print through. Print through is when the fabric weave texture shows through the resin.

Chopped Strand mat does not have much strength. If you need strength you should choose a woven cloth or you could mix the two. Mat can be used between layers of woven fabric to help build thickness quickly and aid in all layers bonding well together.

If you have any questions feel free to comment.  We will do our best to reply with an answer. Or, you can visit our product website Fiberglass Warehouse for more information.


31 thoughts on “Choosing Between Fiberglass Cloth and Chopped Strand Mat (fiberglass mat)

  1. Bob Schmidt says:

    I want to cover an old car floor that has some pitting and minor holes. The floor has been protected with PPG DP 90. I think using fiberglass cloth would be my best option, as it should be stronger and thinner than mat. Do you know of any issues I may encounter? Thanks.

    • fgwarehouse says:

      Fiberglass Cloth would be the best option. A couple layers of the 10 oz cloth with epoxy resin will last a long time. The DP 90 is an epoxy primer, so epoxy resin should be used. Depending on how long ago you applied the primer, you may need to rough it up a little.

      • Bob Schmidt says:

        Thank you for the reply. I applied the DP 90 over 20 years ago, but will lightly sand/roughen up before applying the cloth and resin.
        Would the 1200 resin and hardener, along with the 10 oz. cloth, be a good choice for my use?

        • fgwarehouse says:

          That would be perfect. I would used to 80 or 120 grit to roughen it up. Be sure to clean it with acetone afterwards.

  2. Nick Cantrell says:

    Hi, I am planning on making aftermarket bolt-on fender flares for a car. The shapes do have contour and seams but no complex geometry. The fenders need to be durable but also light. What type of layup would you suggest?

    • fgwarehouse says:

      Chopped strand mat will always be the easiest and cheapest to use. I would still recommend using chopped strand mat against the mold, then a layer or two of 6 oz cloth, depending on how strong it needs to be. If you want superior strength, use vinyl ester resin. It’s characteristics are similar to epoxies.

  3. mario r miralda says:

    I want to repair my swimming pool in ground what kind of fiberglass mat I have to use how much fiberglass mat I need in my swimming pool in ground 35″5″ length ×15″8″width 37″shallow 6″4″deep thanks

    • fgwarehouse says:

      Hello Mario, I calculated roughly 122 square yards that you will need. First off, what is the problem? Are you just redoing the surface? Is the surface cracked? Is the gel coat peeling? You will also need to choose a type of resin. You need a minimum of ISO resin and our guard gel coat.

  4. mario r miralda says:

    hi yes I want to redoing the surface and floor it has holes in the walls floor is cracks thank you for your help

  5. Edward Atha says:

    I’m building a large vivarium and want to fiberglass it rather then paint it the cage dimensions are 70″ W x 24″ D x 48″ H it’s my first time to use fiber glass any help much appreciated

  6. John Berenyi says:

    I have a 1974 Corvette that needs its lower spare tire tub repaired. There is about a 3″ hole through the tub probably from it dropping down on the ground while moving. What kind of fiberglass should I use to repair this hole?

  7. Dave Russell says:

    I’m building a canal boat out of plywood,(34ft).
    It will be structurally strong but needs to take the odd scrape against concrete.
    Finish not important…… Waterproofing is !!
    I was thinking of building up layers of mat with a black pigment.
    Am I doing the correct thing and if so how many layers/weight.
    Regards Dave

    • fgwarehouse says:

      If this was my boat, I would use a couple layers of style 7500, 10 oz fiberglass cloth. BUt were it starts to curve up in the front, I would probably add 2 or three more layers. Even though it is more expensive, I think you will have better luck using epoxy resin. Our Epoxy 1300 would do great. It is a 4:1 system that has excellent waterproofing capabilities and is very strong. YOu can add black pigment to it also.

  8. Matt says:

    Hi there,

    I want to install a skylight on a campervan that has a fibreglass roof. I am going to bolt the framework to the roof supports but need to build fibreglass up the sides to keep the water out and provide some strength. Do I need to use cloth or will strand mat do the trick?

    • fgwarehouse says:

      Epoxy will do the best adhering to the framework. So you will need to use fiberglass cloth, like the 6 oz Style 3733. If you don’t want to go with the expense of the epoxy/cloth. Vinyl Ester resin is the next best resin. It is almost as waterproof as the epoxy. And you can use chopped strand mat. You can also use Orca 301 ISO resin with good results also. With the vinyl ester and ISO resins, you can use gel coat over top of it. The gel coat is UV protected. The epoxy should be painted over with a UV protected polyurethane paint.

  9. Mark says:


    I need to reinforce an area on an old jet ski that is SMC. What would be the preferred fiberglass and I’m assuming epoxy resin only? Also what type of prep would need to be done before applying the fiberglass. Thanks for your help.

  10. Nick B says:

    I want to make a standing platform on top of my canoe. The surface area will be approx 40”wX 60” l. What is my best option for strength. Thickness won’t be an issue so I can do layers. I haven’t decided if I’m going to use a polyurethane/ styrofoam mold (for insulating properties, or just use a plywood frame. Also what resin would be best for strength with both and water proof for plywood?

    • fgwarehouse says:

      For strength and waterproofing, epoxy is always the best. If you don’t want to spend the money on epoxy, go with vinyl ester resin. It is much better than polyester resin and almost as good as epoxy. And also much cheaper. Also, you can cover it will gel coat afterwards to help protect the fiberglass.

      As far as plywood or styrofoam, the plywood will be stronger, but also heavier. If you use styrofoam, you will need to go with epoxy. All the ‘ester’ resins will eat the styrofoam.

      Let me know if you have any more questions.


  11. Steven G says:

    Hello, I am trying to cover an exterior deck staircase with fiberglass, mainly to help waterproof under neath the stair area. Can you recommend whether to use cloth mat or fiberglass strand? Thank you!

  12. Tony Pinder says:

    Hi, I am about to embark on building an 8ft plywood dinghy. My main concern is weight. I am thinking of using 1/4 inch marine plywood and other lightweight wood. What do you reccomend I use to finish the hull plywood and still maintain some degree of lightness? thanks

  13. Scott D says:

    I am replacing the floor of my run about boat. I have 3/4″ marine grade plywood for the replacement.
    Not necessarily needing strength just water proofing that I can add carpet to. What would be the best fiberglass type and thickness as well as the appropriate resin/epoxy system?

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