How to fix a chimney breast
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A common problem is chimney damp.We get a lot of questions about how to stop the damp patches around the chimney.
The symptoms of chimney damp are similar to regular damp but will be isolated around the fireplace or chimney breast.The signs include:
It is easy to identify chimney damp problems, however finding the cause is more difficult.
The use of a ladder may be necessary in order to thoroughly check your chimney and building.You should only use ladders when it is safe to do so and you have the necessary training to complete the job.We would always recommend hiring a trained professional to carry out the investigation on your behalf if you don't feel confident or have another person to supervise and steady the ladder.
In a similar way to other damp issues, chimney damp is usually caused and diagnosed.chimneys can experience other damp causes
The cause of the chimney damp needs to be addressed before damp proof can begin.Some situations can be hard to spot, so your checks will have to be thorough.There can be more than one cause.
A good indication of where to start looking for the cause is the visual signs of chimney damp.
Tars and salts are deposited into the chimneys of older homes when burning coal and wood.Over time, this process can cause chimney damp.
The first thing to look for is whether the chimney pots are open or capped.If they are open-topped and you don't have a chimney, it's possible that rain or water can enter through the opening and cause damp in the chimney.If your chimney is capped, look for signs of damage.
In the case of open or damaged chimney pots, add a chimney cap to protect the stack from letting in water.It's important that you don't seal your chimney at the top if you want to encourage air flow.
Can a blocked chimney cause damp?If there is little or no air movement, the answer is yes.
When your house warms up, condensation forms on the chimney breast surface due to the lack of Ventilation if your chimney is capped and sealed at the top.
Venting unused chimneys at the top and bottom allows for a constant flow of air.The best way to keep the rain out is to fit a terracotta cap to the chimney pot, which allows the air to enter.The chimney vent needs to be installed below the ceiling in the room below.
Next, check for any cracks in the pointing of the chimney stack if you have both capped chimney pots.Water and moist air can enter the stack and cause damp in the chimney.The chimney stack and surrounding brickwork will need to be repointed if this is the case.
Recent home renovations, such as the installation of a wood burner, may be causing damp in your home if you share a chimney with your neighbour.To identify this problem, speak to your neighbours.This may become a problem for them in the future, so the earliest this issue can be identified is better for both parties.
There are brown or yellow marks on the walls and ceilings surrounding the chimney that are caused by a water leak or building fault.There will be more on this later.
The next step is to assess the surrounding area after checking the chimney.The source of the chimney damp doesn't have to be on the stack.
The weather has exposed the chimney on older properties.This can lead to a degradation of the brickwork and also the mortar joints, which can be cracked, making them more absorbent and leading to damp getting in and possibly tracking to internal surfaces.
If the source of the damp is found to be penetrating damp, we recommend that the chimney is checked and repaired where necessary to stop the further flow of water and protect the area from the effects of weathering.
Ensure you check the flashing around the chimney stack for any damage.This can be found inside the attic or roof space.Weak or cracked lead flashing is a sign of water leaking or a build-up of hygroscopic salts.
The chimney will need to be damp proof before the Flashing can be repaired or replaced.If you feel confident, you can either hire a professional or use a homemade tape to repair the damage.
Remember to check your entire roof, not just the chimney stack area, for broken or missing tiles.The tiles in your home need to be replaced to protect it from the elements.
Water can collect in unwanted areas and enter through cracks in the mortar, causing numerous damp and structural problems throughout the home, including chimney damp.The problem can be fixed by moving the downpipes away from the property.
If you have stains and damp marks around the base of the chimney breast, no more than 1.5m high and salt tidemark, this could be a sign of rising damp caused by a bridged damp proof course or lack of DPC.Below are the possible causes of rising damp.
It's not uncommon for older properties to be built without a chimney DPC, we've even seen new or replacement chimney harths installed below it leading to rising damp.If you don't have a chimney DPC, the damp ground beneath your chimney can cause the stack to rise.
If you have a DPC, you should check the area for anything that could be related to it.It's a case of making good the effected areas if any of the symptoms are visible.
Most of the time when dealing with damp chimneys you will need to address hygroscopic salts that are within the masonry, render and finishing plaster.The hygroscopic salts can remain in situ even if the source of the damp has been fixed.The home owner might think the issue has not been solved.
It is important to remove the salt contaminated plaster and render and use one of the below damp proof methods to deal with the problem.
The removal of the render back to the exposed brick chimney breast is required when damp proofing a chimney.If the problem is rising damp, you only need to remove the render up to 1m minimum or 300mm above the last sign of damp.The two most popular solutions are below.
It is possible to install a meshed damp proof membrane to the chimney breast.The salty background is isolated by applying a DPM directly over the area.Installation of the Platon and PermaSEAL Membranes can be done straight away.
Apply two coats of PermaSEAL Tanking to the area as per the data sheet and then apply a minimum 10mm coat of Renovating Plaster over the surface to form a salt-resistant barrier.Pick up Multi Finish Plaster.
It can be difficult to tackle the problem of chimney damp.We are more than happy to discuss your issues and find a solution if you can't find the information you need to fix your damp problem.
We have more than 28 years of experience in the damp proof industry and can help you get the job done.We can give non-partial advice on the products.If you have more information, please contact us.