Woodworm treatment.

[Radio Fixer]

Fortunately I have not had problems in the house with woodworm. Some of the radios had evidence of it, old holes and not knowing better I injected them. The last one was even painted all over on the inside. I will have to re-think these actions from this thread.

From what has been said I should no longer have a problem in a low humidy house but will check for dropping rather than holes.

I get callers wanting me to have cavity wall injection a lot of times but have always said no. I like the draught in the cavities and have made sure they are not covered over in the loft. The house was built that way so let it say that way.

My neighbours, in a similar 70's house, didnt and had cavity fill with overfill into the loft and then massive loft insulation and later found the joists and everything in the loft dripping with water. So they got the installers back whose remedy was to lift some of the tiles, cut the tar paper and install vents under the tiles!

Fortunately they dont have water tanks in the loft.

But I'm glad I said "No"

Gary

[Mark Hennessy]

Hi Gary,

That's extremely wise of you

Jeff Howell is also very vocal about cavity wall insulation, and believes that there is no satisfactory way to retro-fit insulation to a cavity wall. OK, it's fine if the walls were originally built that way - they have a much larger gap, and the sheets of insulation are firmly bonded to the inner leaf with the wall-ties - but anything used to fill the gap will cause bridging...

Cavity walls were first used in coastal areas to reduce wind-driven rain ingress. The idea was that water would penetrate the outer skin, then trickle down the inside of the outer leaf. As the cavity is (or should be) well-ventilated, the water would harmlessly evaporate away.

Interestingly, a single-skin (4.5") wall is guaranteed to leak, no matter how well constructed it might be. The problem is thermal expansion; when the bricks cool down and shrink slightly, gaps open up in the vertical sections of mortar (the "perps").

Anyway, cavity walls were never intended to be thermally efficient, and indeed, they're not especially. If the cavity is ventilated, the air in the cavity is not much warmer than the outside air, so you're relying on the inner leaf to provide the bulk of the thermal insulation (some of the modern blocks used are pretty good compared to traditional red brick). As an aside, I wouldn't be surprised if a house built with solid 9" walls was better than a house made with early cavity walls - providing the walls are totally dry...

Of the cavity wall insulation that is generally fitted, the most common is mineral fibres that are blown in via small holes. These work like fibreglass and Rockwool; by trapping air. But these only work when they are dry - as soon as the fibres become wet, they lose all their insulation properties. And, because the cavity is no longer ventilated, the fibres take a long time to dry. The result is a cold spot on the inner leaf, which inevitably attracts condensation.

Another problem is caused by gaps - invariably there are areas that don't get any of the infill - especially around obstructions like windows and doors, and wall ties or lumps of mortar that fell into the cavity during construction can cause these problems. These also cause cold-spots on the inner leaf.

Also, mineral-fibre insulation can settle with age, causing gaps at the tops of the walls. And as the lower levels compress, less air is trapped, so the insulation value falls away. This can be a problem with timber-framed houses too - frequently mis-diagnosed as a roofing or penetrating damp problem.

Yet another problem is that a lot of houses have their joists socketed in the inner leaf, so when you block up the cavity, you run the risk of rot forming in the ends. More modern houses use metal joist hangers, of course.

At least fibres can be removed (expect a massive industry to emerge over the next few years, specialising in removing them). Some people inject expanding foam, which is more or less impossible to remove - while these should be better when wet, gaps and cold-spots can still occur. Some houses are insulated with tiny polystyrene beads, and these fall out in copious quantities when you drill through the wall!

Finally, over-insulating your loft is a bad idea because the timbers above the insulation will be proportionally colder. Which means they will attract condensation - perhaps not enough to be dripping wet, but damp they will be. And what do we know about damp timber? Yes, back to the topic of this thread - our local beetle population will soon set up home in them. And they will be much more susceptible to rot as well! I really wish the government would listen properly to the people advising them, rather than just picking out the bits they want to hear!

We have 4" of insulation in our loft, and I will be putting no more down on the top of the ceiling. I'm willing to put sheets of foam insulation (Kingspan or similar) between the rafters to insulate the slopes themselves. We have 4" timbers, so 2" sheets will be perfect (building regs call for a 2" gap between insulation and the roof surface. When the place was re-roofed about 15 years back, they used a plastic sarking layer with lots of tiny holes that make it breathable yet waterproof, so I'd be confident that the timbers will remain in good condition. Having a bit of warmth up there will hopefully help my collection of radios and other junk survive until the kids leave home and I can start doing electronics again :-)

All the best,

Mark

[pwdrive]

Hello Mark, you are in my view correct about not filling cavity walls, the cavity is there for a reason as you say, if the wall is not exposed to the elements for whatever reason then it is possible to do it with no real ill effects but that scenario does not happen very often, to seal everything up is madness but that is what people tend to do, they build houses the wrong way round it's all vested interest driven I'm afraid, in my view the cavity should be a lot wider in todays construction thus allowing a greater thickness of slab insulation to be fitted whilst still maintaining a satisfactory air flow, we have the technology to build decent energy efficient housing but for whatever reason it's not used.
You can beef up your loft insulation by the way but you will need to ensure that the roof is ventilated for it's whole length where it makes contact with the wall plates ie: between the rafters, there are various plastic vent systems available or you can make your own up using thin plywood and timber batten, the vent should vent to a vented soffit if possible, if you upgrade then as you say Kingspan or Celotex is good stuf with some rockwool on top, all my wooden floors are insulated with kingspan laid in between joists on batten ledgers.
I have spent a lifetime doing up old properties both for ourselves and other people, we have lived in roses round the door cottages and converted stone barns etc, trouble is you have to heat up 200 tons of rock before you can heat yourself up, what's that all about. We were fortunate enough to aquire the place we are in now which is mainly timber based, it easy to keep it warm whilst maintaining enough ventilation, all the windows I put in are fitted with trickle vents and we spent several thousand pounds on insulation alone (Kingspan & Rockwool) but it has been well worth it, the place keeps bone dry.
If anyone has down stairs walls that are solid and not cavity then you can convert them to cavity either by using timber frame (you have to know what you are doing) or lightwieght block such as Thermalite/ Durabloc etc, we did this at the last property we had which was a barn conversion, two of the downstairs outer stone walls were below ground level (barn built into side of hill) I allowed a cavity space (air) and built the Thermalite wall straight off the concrete floor (with DPC) every other course was tied to the stone wall with SS screw in wall ties, the cavity was vented to outside at the front and one side of ythe house (the walls that weren't below ground level, the result was absolutely no damp whatsover, not even after 20 years. You can cut Thermalite, Durabloc etc with an old gash handsaw.
Below is some of my handy work from a barn we converted.

Lawrence.

[Radio Fixer]

Thanks Mark and Lawrence for very interesting information. Glad to know I'm on the right track.

Gary

[Retired]

Hi,

Nice one Gary; I too will never have cavity wall insulation for the reasons stated and I'm sure Mark will be proved correct in years to come when a new industry springs up with lots of firms removing failed cavity wall insulation. I don't even trust the new generation cavity wall insulation built in from new in the form of slabs. Cavities are there for ventilation and even mortar dropping on the wall ties can cause problems by bridging. Thanks for bringing this subject up Gary as it's brought in some very useful information.

What a splendid home you have Lawrence thanks for sharing the pictures it is very well presented indeed and a credit to you. I bet there was a lot of huffing and puffing going on during installation of the stone fire place.

We have 12" loft insulation which has been great as it retains heat during winter and repels heat during summer; I've not noticed any down side due to damp. when I installed the new roof 23 years ago I "counter battened" the Marley Wessex tiles thereby lifting the tiles from the felt membrane allowing increased ventilation and I also added full length eaves ventilation strips. Additionally I added 1/2" thick exterior grade plywood strips along the ends of the rafters where they abut the fascia boards to prevent the membrane from sagging forming pools or ice dams.

A personal thing I dislike is plastic window frames; doors and cladding and I'll never install any of these. I prefer timber and all our window frames are original timber and in good condition; the double glazing units now need replacing but not bad as they have been in since the mid sixties. I don't want to live in a Lego house. I think it very amusing that much is said about modern double glazing then to add the window slot ventilators which appears to contradict the virtues of spending a fortune on double glazing.

Plastic doesn't last forever so what will happen to the millions of plastic window frames and doors in years to come; bigger landfill sites?

One thing I'm currently researching is pointing. Previously I've pointed using a mix of Portland cement; Hydrated Lime and sand. 1 x cement; 2 x Lime and 5 x sand. The random stone of the bungalow shows no signs of distress with this mix but as I need to re-point a full wall I would like to use a lime mix only but as I read about this there are downsides as a lime mortar takes quite a while to set and given that we suffer lots of rain I'm worried about such mortar washing out and making a mess of the stonework. A strong cement/sand mix is sure to destroy the wall so I need to be very careful I don't do more harm than good. Any information on lime mortar would be most welcome together with any websites.

With building materials being readily available it is very easy for a novice to jump in without first researching the subject as a lot of damage can be caused to a building.

Kind regards, Col.

[Mark R]

I found the attached beetle ID guide ages ago.
it may be of some interest.


  woodworm_guide.pdf (Size: 87.65 KB / Downloads: 93)

cheers Mark

[pwdrive]

Hi Col, I wouldn't worry to much about a lime mix, personally I think it's over hyped, all the pointing I did in that barn picture was done with your standard 3 to 1 cement mix, we never had no problems with it, yes that stone fire place was a bit of a grunt to construct I picked the granite linlel up for a fiver when we first bought that place, wouldn't get much change out of one hundred quid today. We put that lintel up Eygyptian style.
There is nothing to fear about modern slab insulation in modern cavity walls, it's 2" thick and tongue and grooved, the cavity wall is constructed with a 4" cavity, they are fixed to the inner wall with non degradable clips that clip on to the SS wall ties, the clips are designed so that no water can pass by them on the wall ties, this still leaves a 2" permenant air gap between the outer face of the insulation and the outer wall of the cavity. A good builder or DIYer will lay blocks/bricks etc with very little in the way of cement droppings going down the caviity and to be really sure will hose out the cavity at the end of each shift to make sure the cavity is kept clean during the construction, any muck being washed out along the bottom and exiting through a gap purposely left in the bottom course which is filled in when the wall is finished.
I personally think that all new houses should be built facing south with a high thermal mass and incorporate plenty of glass for solar gain, ie: passive solar heating, trouble is most folks want something that looks "traditional"
As a testement to slab insulation in cavity walls: The end wall of the house we are in now was a single leaf wall being a mixture of shuttered concrete,chicken wire, bricks, cement and old paving slabs stood on end! The usual bodge up, I rebuilt this wall with block cavity construction with Kingspan slab insulation fixed to the inner leaf, I have not had time to render up the the outside of the outer leaf yet so it is totaly exposed to the rain, we have had a real battering with the rain this year with gale force winds behind it, there has been no damp penitration to the inner leaf at all, so I would say slab insulation in a new wall is good and is about the best you will get for cavity insulation.
However as has been said there will in many cases be some negative long term effects by filling an existing cavity completely with beads, foam, fibres or whatever. In my opinion the only way to improve the U value of an existing cavity wall is to insulate and clad the outside (planning problems almost guarenteed) or insulate and dry line the inside (marginaly reduced floor area)
Also if the cavity has been filled can you guarentee that no fill has gone below the DPC, if the fill has filled up the cavity from cavity bottom then I think long term there will be problems for sure due to long term capillary action bridging the DPC, the first casualty in that case will be the back of the skirting boards going rotten.
A lot of this damp proofing stuff is blindingly obvious but may not always be blindingly obvious if in a rush to show off your DIY skills, good hat and boots, dry walls and good ventilation = a healthy house, simples. As Mark has already pointed out a lot of damp is taken as rising damp when in fact it is condensation, if the ground level outside the house is below the floor level then in general any rising damp will not go up much more than 2 to 3 ft if that. When I used to do site carpentry on old conversion/refurbs etc the building regs was to damproof an old solid wall up to the 4 ft level, in the early days it was newtonite lath or sand blinded synthaproof, today a lot use thoughroseal which is really good stuff and not as messy as synthaproof. A common method today is to use thoughroseal then dry line using metal C channel studwork with vapour barrier and plasterboard. Condensation can soak a cold wall head to foot no matter what its construction is.

Good luck with the DIY/renovation Mark.

Lawrence.

[Mark Hennessy]

Hi Lawrence,

Wow - fantastic pictures! My "renovations", if you can call them that, are much more modest in ambition - all I want is to get the house back to the state it was in before all the recent bodges that took place. At the moment I'm sorting out the plumbing - it's amazing how previous plumbers sent pipes all over the place rather than taking direct routes - presumably because they couldn't be bothered to lift more than a couple of floorboards. I keep meaning to start a new thread about all of this - one day...

Col, I must admit that I use lime in my mortar - I use 1:1:3 lime, cement, building sand. From what I've read, if you plan to add lime, it's best to use these proportions - apparently adding more lime makes it too weak, and if anything, you'd be better going for "pure" lime mortar. Because I live in an old house that was originally constructed using lime mortar, I feel that this is what I ought to be using, but I haven't got around to trying it yet.

My understanding is that one should use sharp-sand with lime mortar, rather than builders sand, which is finer...

I also understand that one should make a lime putty before mixing with the sand. I believe that this involves pouring hydrated lime (the standard stuff you can buy from builders merchants) into a bucket and mixing water into it. Providing you make sure there is always a layer of water covering the putty, the stuff stays good for ages - the chemical reaction is with the carbon dioxide in the air, and it does take a while to go off - certainly a lot longer than cement.

There are a few houses around here that have been re-pointed in hard cement, and all the bricks have spalled as a result, leaving perfect rows of cement mortar protruding from the wall. Certainly, I'd be wary of using 3:1 sand/cement on this building. But for new bricks, it's a bit questionable - I build a small garden wall about 5 years back, and spent ages getting a perfect result - but sadly the frost has got the mortar (which was 1:1:3 lime, cement, sand). I'll need to re-point soon, and I'm wondering if I should use 3:1 sand/cement?

Another factor is that our house has had quite a lot of movement over the years, and the lime mortar has been very tolerant of this - there are no broken bricks, for example. Cement mortar would just crack, whereas lime is self-healing to a large extent (as it forms lots of microscopic cracks that expose the mix to carbon dioxide, which is able to set).

As to what you should use Col, I think it really depends on how tough the bricks or stones are. Aim to use something that is softer - remember, mortar is sacrificial. I'm not sure that the lime would mark the stones if it was washed out by the rain, and in terms of setting time, you're talking about a couple of days (I guess), so you should be OK if you can trust the weather forecast. The worst part about re-pointing is raking out all the old stuff - most people don't do enough of that - I think you need at least an inch. Cement-based mortars are clearly much hard to clean out, whereas lime can almost be washed out with a hose...

Cement-based mortars are less breathable too, so if the wall is solid, it's worth considering lime instead.

But as I said, I haven't yet tried this myself, so the above is just based on what I've read (which is a lot!) rather than practical experience.

All the best,

Mark

[pwdrive]

Hi Mark, sorting out previous bodges is the worst part, I just tend to rip the lot out and start again, that barn in my pic was just four walls and a collapsed roof when we bought it with an omnia cast floor for the first floor (extreemly strong), as regards to lime, well it's subjective like most things, down here with old buildings brick is a rarity and granite is the norm, a cement mortar is ok with that but the purists will use a lime based mortar, for rendering up old walls I have used cement mortar for the inside and had no problem, I have always done that with a weak mix, I have never rendered an old stone wall externally as I have found that it is a major cause of damp penetration if any cracks should appear as they most certainly will at some point ie: water gets in but can't get out, good luck with the plumbing are you going plastic or copper? The house we are in now is more or less a full refurb job, all the basic stuff is done new roof, new timbers, insulation, plumbing and c/heating, windows, doors etc, in my experience it's the finishing off that takes the real will power and effort, in all the properties we have lived in we never finished them off until we decided to sell them...cash is a wonderful motivator! We are thinking of building a small extension for my radio room I want to do timber frame clad externally with a render backing board then rendered with a polymeric mortar, I am familiar with all the brand names etc but I am wondering if you or anyone else has had any practical experience with this method.

Lawrence.

[Mark Hennessy]

Hi Lawrence,

I agree - rip out the bodges! I'm using copper - much as I can see the appeal of plastic to some, and indeed I might use it for temporary things - I'm not sure I can trust the rubber O-rings to last the life of the house. Whereas solder joints and compression joints are very reliable - even when I've done them

Recently we had a new boiler fitted at work, and they used copper crimp fittings. I hadn't heard of these before, but they seem to consist of an O-ring fitted inside a copper fitting, and a special tool that squeezes the fittings, clamping the pipe. The O-ring provides the seal, and versions are available for gas and oil as well. While they look nicer than the plastic fittings, it's still a case of relying on the O-rings. Time will tell, I guess

I think you're right in the case of granite - which is tougher than even the strongest cement. But, would you use cement with sandstone? It's horses for courses, definitely. Modern red bricks are pretty tough, but the old ones much less so. I guess an experienced bricklayer would choose a mix according to what he finds on site - but it's true that there are people who are practically religious about the use of lime.

External renders are generally a nightmare - when looking, I actively chose to ignore any house that was rendered.

And you're right about the finish. But so many people rush the finish and effectively ruin all their previous hard work. I've disciplined myself to take extra care at the finish stages, but that does cause me to put them off! Besides, totally finished houses lack character. Or so I tell myself

No, I've no experience with rendering timber-frame buildings. I've researched the opposite; my "shed" will be close to a boundary, so needs to be made from fire-proof materials. So it'll be made from blocks, but clad in timber so that it looks like a shed. By using blocks, Building Control will be happy to leave me to get on with it, thus saving me money - and I like the idea of the extra solidity provided by that. The foundations might be a pain, but probably worth it. If it ever gets done :-(

Cheers,

Mark