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Fix Gap Between Driveway & Garage

The gap between a concrete driveway and the garage floor is an expansion joint. The expansion joint allows concrete slabs to expand or contract with less or no stress. But every now and then you need to fix the gap between driveway and garage. 

You can fix the gap between driveway and garage in 5 easy steps. It is a simple DIY project that takes just few hours. 

Fix Gap Between Driveway And Garage
GMS Intro
GMS Intro

Why Does The Gap Between Driveway & Garage Need Fixing?

The gap between the driveway concrete slab and the garage concrete floor is there to absorb the stress created by expansion & contraction of concrete slabs due to fluctuation in temperature. Without the gap the cracks in both the concrete driveway and the concrete garage floor would grow in size and propagate.

The process will be hastened if the temperature swings between day and night are large and there is also some moisture moving up from the ground due to capillary action.

“concrete does indeed expand when it gets hot or when the moisture content changes” 

Concrete Construction

The gap is filled up by a flexible material, which permits expansion & contraction but stops water, debris and insects from entering the gap. 

Entry of water is particularly detrimental to the durability of the concrete. There are 3 ways water hurts concrete:

1. Chemical Reaction:

Cement is alkaline and the coarse aggregates (sand & gravel) have silica. Alkali reacts with active silica to form a gel. This gel can then absorb water, swell and apply pressure and cause concrete to crumble.

2. Freeze-Thaw Cycle:

In regions where temperatures drop below the freezing point, water in the gap goes through a freeze-thaw cycle. The freeze-thaw cycle causes stress in the concrete and makes cracks grow.

3. Rebar Corrosion: 

Water in the gap can seep into the concrete pores and corrode the rebars or wire mesh. Corrosion is more severe if the water has salt (in coastal regions or use of salt based deicing chemicals).

However, the flexible filler and sealant deteriorates with time, UV radiation & chemical degradation. This is why, every once in a while, you need to fix the gap between the driveway and garage.

So here are the 5 easy steps you need to take to fix the gap between the driveway & garage:

STEP 1: Assemble Equipment, Tools & Supplies

Assemble all the equipment, tools and supplies you will need for the project as per the list below:

Equipment & Tools You Will Need

  • Shop Vac or alternatively a Pressure Washer
  • Screwdrivers, Putty Knives, Trowel, Metal Brushes
  • Caulk Gun

Supplies You Will Need

  • Polymeric Sand
  • Closed-cell Foam Backer Rod
  • Polyurethane Self-leveling Sealant

STEP 2: Prepare The Gap

The gap between the driveway and the garage will be full of dirt, dry leaves, rotting twigs, dead roaches to name a few. And then of course there will be the remains of previous filler material.

You start off by getting the gap as clean as a whistle!

The easy option is to use a pressure washer. However, I do not recommend it as it is not thorough. The manual way is to clean the gap using sharp objects such as a screwdriver, putty knife, wirbrush, etc. Whatever you have on hand & whatever works for the situation.

Use the shop vac to suck out the loose debris as you claw it free.

Try not to leave anything behind, including any small pieces of the concrete which may have broken or flaked off. Break off loose pieces with a chisel, if required.

STEP 3: Fill in the Cavities

It is quite likely that you will discover cavities and voids that you had not bargained for. It is not unusual for the base sand to settle and subside as water drips through the gap. These voids should not be ignored.

You could fill the cavities, deep within the gap, by pouring regular sand in the gap. The sand will find its way into the cavities. However I recommend using “Polymeric Sand” rather than regular sand.

Polymeric Sand consists of fine sand mixed with silica additives. The additive gets activated when water is sprayed on the polymeric sand. It forms a hard, gel-like compound and creates a permanent bond between the sand particles.

Though more expensive than regular sand, it lasts for over 10 years as compared to 2 years for regular sand.

STEP 4: Insert the Backer Rod

Backer rod is a flexible rope that compresses to fill the gap. It gives the sealant something to cling onto.It also helps reduce the quantity of sealant that you will need to fill the gap. The backer rod is a lot cheaper than the sealant for the same volume of the gap.

Buy backer rods that are somewhat thicker than the gap width. This way you can push the backer rod into the gap with your fingers or a putty knife and get a nice, snug fit. 

1” Closed Cell Backer Rod should be a good fit for your project. 

Press it in so that it is ¼” – ½” below the concrete surface. This is what the sealant will fill up.

STEP 5: Seal the Gap

It is very important that you seal the gap with a sealant that is flexible. Do not use any sealant or caulk. Flexibility is the key to ensuring the stress created in the concrete due to thermal fluctuations is not translated to crack expansion & propagation. 

Sikaflex Self Leveling Sealant is the most suited for fixing the gap between driveway and garage. It is a single component, self-leveling, premium-grade polyurethane sealant with an accelerated curing capacity. It can bridge gaps up to 1 ½”.

Place the tube inside a caulk gun and start the sealing from one end. Dispense the sealant into the gap, completely covering the backer rod and bridging the gap from edge to edge. The sealant has good flow properties and gets into every nook & cranny.

Remove any excess sealant that may be above the level of the driveway or garage floor using a trowel or putty knife. Allow the sealant to dry thoroughly.

That’s all there is to it!

Thank you very much for reading the post. I do hope you found it informative and useful.

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