---
product_id: 5587474
title: "MD Building Foam Backer Rod, Gray, 3/8in x 20ft for Small Gaps | Closed-Cell Foam, Prevents Caulk Waste, Cuts With Scissors, Blocks Drafts Moisture Dust Insects, Indoor/Outdoor"
brand: "m-d building products"
price: "S$16"
currency: SGD
in_stock: true
reviews_count: 13
category: "M D Building Products"
url: https://www.desertcart.sg/products/5587474-md-building-foam-backer-rod-gray-3-8in-x-20ft
store_origin: SG
region: Singapore
---

# Easily trimmed to fit Waterproof & weather-resistant 3/8in x 20ft precision sizing MD Building Foam Backer Rod, Gray, 3/8in x 20ft for Small Gaps | Closed-Cell Foam, Prevents Caulk Waste, Cuts With Scissors, Blocks Drafts Moisture Dust Insects, Indoor/Outdoor

**Brand:** m-d building products
**Price:** S$16
**Availability:** ✅ In Stock

## Summary

> 🛡️ Seal smart, save big—your gap’s new best friend!

## Quick Answers

- **What is this?** MD Building Foam Backer Rod, Gray, 3/8in x 20ft for Small Gaps | Closed-Cell Foam, Prevents Caulk Waste, Cuts With Scissors, Blocks Drafts Moisture Dust Insects, Indoor/Outdoor by m-d building products
- **How much does it cost?** S$16 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.sg](https://www.desertcart.sg/products/5587474-md-building-foam-backer-rod-gray-3-8in-x-20ft)

## Best For

- m-d building products enthusiasts

## Why This Product

- Trusted m-d building products brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Versatile Home Armor:** Ideal for insulating doors, windows, driveways, and more—boost your home's airtightness and comfort.
- • **Perfect Fit Every Time:** Precisely sized 3/8in thickness ensures a snug, draft-blocking seal for medium gaps.
- • **Effortless Installation:** Push-in design and easy-to-cut foam make sealing gaps a quick, mess-free task.
- • **Caulk Saver Extraordinaire:** Creates a sturdy base that prevents caulk waste and enhances adhesion for long-lasting seals.
- • **Built to Brave the Elements:** Durable, waterproof foam stands strong indoors and outdoors, resisting moisture, dust, and insects.

## Overview

The MD Building Foam Backer Rod is a 3/8in x 20ft gray closed-cell foam designed to fill medium gaps with precision. Waterproof and weather-resistant, it provides a durable, flexible base for caulking, preventing drafts, moisture, dust, and insect intrusion. Easy to trim and install, it’s perfect for both indoor and outdoor use, enhancing insulation and extending the life of your sealants.

## Description

desertcart.com: MD Building Foam Backer Rod, Gray, 3/8in x 20ft for Small Gaps | Closed-Cell Foam, Prevents Caulk Waste, Cuts With Scissors, Blocks Drafts Moisture Dust Insects, Indoor/Outdoor : Industrial & Scientific

Review: Good low cost back rod - Used this foam to seal up the concrete around my 4inch pipe for Radon System before I caulked. I stuffed this around the pipe to fill in the gap and then covered it all with high quality caulk to seal it up perfectly. It worked perfectly and is far cheaper than what i found at my Home Center. Make sure to purchase a thickness that is a little wider than your gap so it make a tight fit.
Review: Works well for insulation also - Stuffs easily into door and window cracks to provide insulation in irregular sized gaps. And works well as intended caulk saver for large cracks.

## Features

- Quality Construction: This gap filler is made from high-quality, weather-resistant materials, ensuring long-lasting durability and performance. It effectively seals medium gaps between surfaces, preventing drafts and dust from entering your home. Suitable for both indoor and outdoor use, it withstands various weather conditions, providing consistent protection and improved comfort.
- Concrete Gap Filling Excellence: Our product excels in filling concrete gaps, creating a strong foundation for caulking projects. Utilize this foam to effectively fill joints between surfaces, ensuring dependable adhesion for caulking applications that promise enduring durability and resilience.
- Complete Gap Solution: This product provides versatile gap filling, preventing drafts and offering a sturdy base for caulking. Perfect for expansion joints in driveways and sidewalks, it can be twisted for larger gaps and easily trimmed with scissors to the desired size.
- Effortless Installation: Enjoy a hassle-free setup by effortlessly pushing the backer rod into most joint openings until it fits snugly. Once installed, enhance the seal further by applying caulk on top—no need for messy sealants or adhesives.
- Versatile Application: From repairing leaky roofs and window sills to addressing drafty doors, the Backer Rod is your go-to solution! Beyond sealing surface gaps, it excels in insulating, enhancing airtightness, and damp-proofing your home—offering multifaceted benefits for various household needs.

## Technical Specifications

| Specification | Value |
|---------------|-------|
| Brand | M-D Building Products |
| Color | Gray |
| Item Form | Foam |
| Item Weight | 17.01 g |
| Surface Recommendation | surface_recommendation |
| Water Resistance Level | Waterproof |

## Product Details

- **Brand:** M-D Building Products
- **Color:** Gray
- **Item Form:** Foam
- **Item Weight:** 17.01 g
- **Surface Recommendation:** surface_recommendation

## Images

![MD Building Foam Backer Rod, Gray, 3/8in x 20ft for Small Gaps | Closed-Cell Foam, Prevents Caulk Waste, Cuts With Scissors, Blocks Drafts Moisture Dust Insects, Indoor/Outdoor - Image 1](https://m.media-amazon.com/images/I/61bhNB8Z9UL.jpg)

## Available Options

This product comes in different **Size, Style** options.

## Questions & Answers

**Q: how many feet come in a 3 pk?**
A: Both INDIVIDUAL packs - the 3/8" and the 1/2"-  are 20 feet long.

**Q: no 1/4" one? either 20 or 50ft?**
A: Not in this brand, but Amazon offers 1/4-inch backer rod in various lengths, from 10 feet to 100 feet, from other brands. Just search on "Backer Rod 1/4 Inch".

**Q: can the backer rod be sliced for smaller openings?**
A: I have not done that, but it cuts easily with a sharp knife or scissors, so you should be able to slice it to fit whatever opening you have. It's good stuff!

**Q: Can his be used for exterior windows before caulking?**
A: I used it to push into larger cracks in my driveway before applying concrete filler, and it worked great. I'm thinking that it should work well for filling in spaces around your windows prior to caulking.

## Customer Reviews

### ⭐⭐⭐⭐⭐ Good low cost back rod
*by U***T on April 8, 2026*

Used this foam to seal up the concrete around my 4inch pipe for Radon System before I caulked. I stuffed this around the pipe to fill in the gap and then covered it all with high quality caulk to seal it up perfectly. It worked perfectly and is far cheaper than what i found at my Home Center. Make sure to purchase a thickness that is a little wider than your gap so it make a tight fit.

### ⭐⭐⭐⭐⭐ Works well for insulation also
*by M***N on February 8, 2026*

Stuffs easily into door and window cracks to provide insulation in irregular sized gaps. And works well as intended caulk saver for large cracks.

### ⭐⭐⭐⭐⭐ Great to fill Concrete Expansion Joints!
*by T***M on July 14, 2016*

So I've been looking around for a way to fix my concrete driveway. Unfortunately the concrete expansion joints have separated and have made a pretty big gap. After much research I found that I should use a backer rod to lay in the expansion joints and than use a self leveling chalk to seal it in. This will prevent any additional water from eroding the base material under the concrete. I needed a couple different sizes as the width of the expansion joints was different as you went up the length of the driveway. I found what I needed. The M-D Building Products Backer Rod. I bought both a 1/4 and 1/2 sizes. I like to tell people about my shopping experiences in this case I'll cut and paste this same review for both the 1/4 and 1/2 sizes I received (no big differences in these). Both the 1/4 and 1/2 inch arrived on time. They were packaged very well. Super light as you can imagine. The backer rod is like a foam material. It fit well into the expansion joints. A nice snug fit. This is exactly what I was looking for. Otherwise with as wide and deep as these expansion joints have gotten it would have taken a lot of self leveling chalk to fill them in. The material cut really easy. I use my utility knife but an ordinary pair of scissors would have worked just fine. I was happy with the quality. I felt confident when install it in the expansion joints that it would hold up just fine and do the job.

## Frequently Bought Together

- M-D Building Products - Versatile Gray Foam Backer Rod - Essential Caulk Saver for Sealing Concrete Gaps, Expansion Joints, and Crack Filling, 3/8 by 20 Feet, (Pack of 2) (71464)
- M-D Building Products - Versatile Gray Foam Backer Rod Set 1/2in x 20ft - Essential Caulk Saver for Sealing Concrete Gaps, Expansion Joints, and Crack Filling (71480)
- Sikaflex Self Leveling Sealant, Gray, polyurethane with an accelerated curing capacity for sealing horizontal expansion joints in concrete, 10.1 fl. oz Cartridge

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*Product available on Desertcart Singapore*
*Store origin: SG*
*Last updated: 2026-08-16*