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Gary, Handyman
Category: Home Improvement
Satisfied Customers: 246
Experience:  25 yrs in home repair/building - 10 yr in live theatre set design/building
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I have a porch extension which has been installed without a

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I have a porch extension which has been installed without a cavity tray, with a consequent ingress of water every time the rain is in the 'wrong' direction.
Are there any systems (injection/chemical) that can provide a solution without pulling out the brickwork?

Hi and thank you for using Just Answer;

I'm sorry but I don't quite understand your question 100%. If you can take the time to answer some questions, it'll help me understand what you are dealing with.

When was this porch extension built? Is it attached permanently to your home? When it rains, you mentioned "the wrong direction" Does that mean that the run off is washing back towards your house instead of towards the yard? What kind of damage are you experiencing now? Where they there prior to you adding to the porch?



Customer: replied 3 years ago.

Porch was built some 40 years ago at the same time as the house. It originally had a flat roof but this was replaced with a single pitched tiled roof some 15 years ago.


Water enters the porch when prolonged heavy rain, driven by prevailing westerly wind strikes the building face.


I have extended the flashing and sprayed the house (brick) face with silicone waterproofer.


My assumption is that after prolonged rain the external facing bricks get soaked with water which then runs down the back (internal) face and in the absence of a cavity tray the water penetrates the interior of the porch.


Thank you for getting back. Has this been an on going problem? Or has it recently started maybe some few years back?

Customer: replied 3 years ago.

Has recently become a more common, has been particularly a problem over the past two years - the prevailing wind direction seems to have shifted over this period!


Thank you for getting back ... How's the cement grout between the brick look? Is it loose to the point that you can just pick/scrap it off with little to no effort?
Customer: replied 3 years ago.

Cement grout (mortar) is fine, seems was mixed with a good cement content and remains hard. The brick is good quality.


Thank you for your answer. Per your answer would it be saft to say that you have no cracks either between the mortor and bricks? Or that your haouse hasn't shifted in such away that you received noticable stress crack? (Referring to inside and out) Another question I would like to poss is this; During the changing season, fall to winter & winter to spring, does your house shift as to where you notice certian doors may close hard, or not at all, or perhaps a cabnit door or even an entry door will close on their own unless held open or maybe if you don't latch the door, it will swing open?
Customer: replied 3 years ago.

No subsidence or stress cracks inside or out.


Just to reiterate, in case we are going off at a tangent - what I was seeking was if information as to whether there is any propriety system on the market that enables the installation of a cavity break or tray (possibly a chemical injection system?) without the need to start breaking out courses of brickwork.


I would mention that I am a retired Civil Engineer and have a grasp of most commonplace fabric problems related to buildings.


Thank you once again for your answer. I have never gotten off target simply because a building can do so many strange things. Per your problem what I was trying to narrow down was basic things/items where water can get into and possible travel to from a starting point. You being a civil engineer knows that water and electricty will take the least restrictive way of travel. Now that travel can be as little as cm to as much as several meters. This being said, I wanted to know how things stood in your current situation.

As for appling the water sealant, it will only creat a Band-Aid effect. No different than appling hot tar to a flat top roof with cracks. All this does is provide "short" term fix and that normally last until the seasons change and the building moves once again. As for your problem, you can do injections, however it will only do more damage down the road. The space that is in between your brick is needed for expansion and contraction. It is also needed for air flow to dry things up so you don't have mold problems to deal with. Once you fill that void, then it will inturn move the point of stress to a different area of your home. So the short answer of all of this would be "no". I wouldn't recomend it at all. If you would inject a foam system 1) you never know if you covered everything 2) not knowing where the water is coming in from allows it to pool up faster between the air pockets you just created by injecting the foam. 3) per problem (2) this will allow water to leak in other places of your home that never gave you trouble before. Pooling water will rot out a house faster than anything and it also invites unwanted bugs and other pest

I'm sorry to say, and I do feel for your problem, but if you are now getting more water than normal in the past two to three years then certian things must be done. As brick and mortor age they become more course. The change in weather patterns don't help any either. You would be far better off installing the cavity trays. I understand the mess, cost and frustrations that goes along with doing something like this, however, your home will be far better off. Having a cavity tray will allow your home to breath better and have better air movent thus keeping things dry. This will also assure that you don't have water "pooling" anyware between the brick and the inside of your house as well.

I wish you the best.

Gary and other Home Improvement Specialists are ready to help you
Customer: replied 3 years ago.



Thanks for your assistance - looks like I will have to bite the bullet (or move!)





Hi Phil,
I'm sorry to be the onethat had to tell you ... however look on the bright side, better that you know now before it became to late. I do wish you well. If there is anything else I can help you with, please let me know.

Take care