Deteriorating mortar is a common problem in decades-old brickwork. Brick and mortar is quite porous and absorbs water like a sponge. When there are loose joints, water gets in. The real damage occurs during the winter months when this water freezes. Just before water turns into a solid, it expands approximately 9% by volume. So a ¼” wide mortar joint that penetrates ½” and is 2 inches long was filled with water, the water would increase the width by about 0.02″. That may not sound like much, but multiply that by 15 joints and this expansion could cause the unrestrained bricks to move by ¼”! This expansion is the cause of failed joints and if not repaired, can eventually lead to a failure of the entire wall.
Don’t only focus on your foundation walls when you walk around your home. You should also take a look at your chimney especially when your home has a high efficiency furnace. High efficiency furnaces no longer use the chimney to vent the exhaust gasses. They use PVC pipes that vent usually outside the home at the top of the basement wall. Traditional masonry chimneys were designed and sized to vent very hot flue gases from old coal, wood burning, or low efficiency gas furnaces. Chimneys are designed to handle the heat and ash from these old heating plants. Once these are removed, your flue may be too large for the orphaned water heater. There are products on the market including flexible stainless steel pipes that can be snaked down your chimney and attached directly to the water heater exhaust. This pipe also has a vent cap to cover the old chimney flue.
In some cases, this can create condensation problems inside masonry chimneys. The water heater does not produce nearly the high temperature exhaust as the old furnace did. If the chimney is too cold, this can condense the water vapor in the exhaust. Sometimes this condensation is acidic and could deteriorate the masonry inside the chimney leading to problems down the road. More importantly, if the air is cold enough, the exhaust from the water heater may not be enough to completely draft out of the house. This could allow some carbon monoxide back into your house which can be dangerous. A chimney that has not been sleeved will eventually fail. A good set of binoculars is all you need to safely inspect your chimney. If you see gaps in the mortar joints or spalling on the bricks, you should have a licensed chimney repair company take a look at it for you and make any necessary repairs.
We suppose you could wire brush the joints to remove the loose mortar and apply a masonry sealer in hopes of stopping the deterioration, but we don’t think this would be a long-term solution. Rather, we suggest that you re-point the joints. This is the standard practice to repair worn out joints and can easily be accomplished by a do-it-yourselfer, even if he or she has limited skills. To re-point the joints it is first necessary to remove the existing loose mortar. We like to use a narrow paint scraper – either a pointed one or one just as wide as the joint – but this is a case of whatever works best for you. Make sure to wear eye protection!
Remove at least 1/2 inch of the mortar from each joint. You may have to dig deeper if the mortar is particularly loose. This is a messy job so use drop cloths to cover the surrounding area. Once the old mortar is removed, mix a small batch of mortar in a 1-or 2-gallon bucket. Make sure you use mortar that is compatible with your existing wall. When in doubt, make sure to speak with your building supply store or contract with a licensed masonry contractor. Mortars around the turn of the 20th century were made up of mostly lime and sand. Portland cement mixes didn’t come into play until the mid 1040′s. Old mortars are significantly softer and if a Portland cement mix is used it could damage the existing bricks. Mix small batches to ensure that the mortar does not dry before you can use it. The mortar should be mixed to the consistency of toothpaste. If it is too thin you won’t be able to pack it into the joints or if it’s too thick it’s hard to work with.
Fill a spray bottle with water and wet the joint prior to applying the new mortar. With a small mason’s trowel, fill the joints with the new mortar. Let it set up a bit, then tool it with a pointing tool. Pointing tools are metal and can either be round or rectangular. They are used to form the finished joints. Mortar, trowels and pointing tools are available at brickyards, home centers and hardware stores.
Clean off any excess mortar you may have gotten on the bricks. We’ve found it best to use water sparingly for this part of the cleanup because using too much water may ruin the new joints you just created. You can use a bristle brush and use strokes that are perpendicular to each mortar joint.
Once the mortar has completely dried – a few hours or the next day is fine – clean off any excess film you may have gotten on the brick with a weak solution of muriatic acid. When doing this, make sure to take all the recommended safety precautions, including wearing rubber gloves and eye protection.
This may sound a bit complicated but it’s really not. Applying the mortar to the joints can be a little frustrating at first, but the learning curve is not very steep and your brick joints will look like new fairly quickly. If this is something you do not want to tackle yourself, then look for a professional. We have contractors on our site that would be happy to provide you a quote for the repairs. You may even be able to work with the mason to do some of the work yourself to prepare the joints and have the mason finish the job for you. This is labor intensive and you may be able to save some money by doing part of the work yourself.