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Mud-brick walls can be hard to waterproof

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old brick wall sxc

sxc.hu

Damp damage to homes is one of the most worrisome conditions for potential buyers.

Two readers responded to a recent question about removing glue left on windows when film is removed. Peter said to try Brasso, which is an excellent solvent (but remember it is a mild abrasive). Salma wrote: Use a tin of antiperspirant underarm spray. Apply to a section, leave for 10 minutes then use a thin scraper.

I have no idea why this may work, but if anybody tries it, let me know the results.

Roger is looking for advice on damp: I am a lifelong DIYer. I have a mud-brick house in Paternoster, one of the oldest houses there. But I have wrestled with damp for the past decade. The house is not anything to look at architecturally but we love it.

The walls are around 500mm thick, made of unfired mud brick and plastered in the main with the same. I have tried Coprox and stuck fanatically to the instructions, cleaning the surfaces to plain mud plaster, only to find that the Coprox does not last any longer than bog-standard lime wash. As we inherited the lime wash I am loath to change it. Painting up to four times a year in parts, though, takes away much-needed downtime.

And another question: dDo you have an old recipe for what seems to be a crushed black mussel shell, sand and something else decorative plaster that falls off in clumps from time to time?

Answer: Your second question may be a guide to the first. The fact that you have plaster falling off suggests to me that the walls may be of such a low density that the Coprox may not be able to fill all the voids, and thus water will still penetrate, causing the plaster to fall off and the paint to peel.

Also the fact that you have an old shell plaster and are close to the sea may mean that the product is absorbing chemicals that it is not designed to handle. Even the highest-quality paint will not adhere to the previous coat if salt residues are not washed off between coats.

There are very few, if any, products on the market that will solve damp problems if applied internally; proper waterproofing can only be achieved if the external surfaces are properly waterproofed first.

You could also have a rising damp problem rather than a penetrating problem. The house may not have been constructed with a proper damp-proof course, and even if it was, internal alterations or a build-up of ground level externally may mean that the damp-proof course has been breached.

As to mussel shell plaster, I cannot find much information on it, other than to say that mussel shells are used in certain pre-mixed mortars due to their high lime content.

Colin writes: After reading your article on filters one can install on well-points, I was wondering if you can help me with my problem.

I have been filling my pool with water from my well-point for the past eight years. The water is crystal clear – however, every 18 months or so I find that I have to replace the element of the salt chlorinator.

Last year I was so gatvol that I insisted that Pool Doctor get the supplier to pay 50 percent of the replacement cost; they did and gave me strict instructions on the care of the unit, which I have followed. I have not used acid and only resorted to using my high-pressure hose to clean the element. This, too, has now failed and I find myself in the same position I was 18 months ago. Could the problem be the metals in the well-point water and will this filter you referred to in your article help?

Answer: The answer is I don’t know, but hopefully we will get some response from a pool specialist.

I do know that when I was using bore-hole water to fill my pool, with or without the filter I had installed, the element did block up with salt a lot more quickly than when I used normal tap water, and now that I am back on tap water the element is much easier to clean.

Our final question this week, received via SMS, relates to insurance.

Please advise: I must insure my new semi-detached cottage. It is in an area that should appreciate in value. One insurer says only insure at building replacement costs based on size house plus garage plus boundary wall. This is only two-thirds sale price. The second says insure at market value. I am confused and do not want to over- or under-insure.

Answer: You must insure at replacement cost, there is no question about this. Property values go up and down, but building costs continually increase. Building a cottage in a new development can be low cost initially because it was built as part of a scheme and economies of scale apply, but if you were to remove your cottage and build it as a single unit, the cost would escalate greatly. All too often I have come across clients who find that in the event of a major disaster they are under-insured even though they can produce the initial building costs.

Building insurance is relatively cheap compared to other insurance, so always err on the high side. It is your responsibility and yours alone to ensure that you are adequately covered. One other piece of advice: stick to the well-known national, large insurance companies.

Once again I am going to say it: check that you are using properly registered and compliant contractors.

* Keep your questions or comments coming to [email protected] or sms only to 082 446 3859.


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