Damp, rendering and insulating external walls

FreeBear

VfM4meplse wrote: »

Ok, so another thick and how-long-is-a-piece of string question from me how long does it take for brickwork to dry out thoroughly, assuming it is warm and dry? It bleeps red on the damp meter but there are no obvious signs / smells of damp inside.

The damp meter (assuming one of those gadgets with prongs on one end) are only good for giving reliable readings on untreated wood. Whilst they can be used to give comparative readings on other materials such as plaster & bricks, paint, salts, and even the chemical composition of the material can and will affect the readings.

A rule of thumb for drying out a wall is 25mm (or 1") per month, so nine months for a 9" thick wall.

VfM4meplse wrote: »

Lime plaster seems the most appropriate solution, but the pictures I have seen of it suggest a "lumpy" appearance. None in the 2 facing rows of same-style houses have this appearance, I can see that they have all strived for smooth (they are in various states of repair). So can lime render give an even finish?

Lime plaster can be finished to a high gloss finish with the right type of plaster and application of soaps & waxes - Have a look at Venetian Plaster for some inspiration. Externally, a sandpaper texture is recommended for various reasons. A reasonably skilled tradesperson should be able to produce a smooth, flat finish. An example -

snowcat75

Hydraulic limes "work" the same as cement although iv used more pit sand than plastering sands with them to get the colours correct.


As for insulation my first home was a 9" solid 50s bungalow fridge in the winter hot in the summer I insulated with just 25mm of high density panals inside and combined with roof insulation which I did when I put dommers in I could heat double the space for half the cost!!!


since then iv converted barns and lived in them current is 400 m2 on solid on 14" walls I put 100mm of cellotex 50mm air gap on the walls 260 mm in the roof and 70 into the floors heating with uhf is less than £300 a year.


Internal insulation done correctly WILL cure the damp and in the long run save £1000snds, yes I can understand the mess etc, but certainly worth considering.

VfM4meplse

Can I throw something else into the mix: would adding air bricks make any difference to the accumulation of damp? Is it safe to add these to an existing wall?

FreeBear

Air bricks to ventilate the void under the ground floor is always a good idea. Adding an air brick might be needed if you fit a wood (or multifuel) stove. Just adding air bricks to increase ventilation of a room is not a good idea in my opinion. You will end up with a cold draught, an entry point for bugs & pests, and a duct for exterior noise to enter the building.

If you are wanting to ventilate and control damp, a heat recovery ventilation system would be much more desirable - The heat from the warm, damp air is extracted and used to heat up the incoming cold air. A suitable system need not be hugely expensive.

cs95aam

FreeBear,

Do you have any experience in heat recovery systems? I've been recommended to install one by Building Forensics following an assessment on mould in our 3 bed property.

Thanks

FreeBear

cs95aam wrote: »

Do you have any experience in heat recovery systems?

Afraid not. It is one of those jobs on my "to do" list, and judging by comments here and on other forums, it can make a big difference for a relatively small cost.