Survey outcome - advice please! :)

[sidehaas]

Oh, and on the initial damp concern, he also said that it was possible the damp had spread to the timber underneath the original) suspended wood floor in the dining room, and recommended we get this checked out. Does anyone know how easy it is to do this sort of inspection and whether it could be done without pulling boards up? If its that simple I'd like to do it myself...

I will probably call the agent and see if I can go round again for half an hour and look at these specific thigns myself, but Im no expert.

 

[stuart45]

Damp at low levels on a wall is often caused by condensation, high external ground levels, leaking pipes etc. The failure of a DPC is very rare. Injected DPC's only slow down the moisture, they don't stop it. You need more than a damp meter to give an accurate diagnosis.

 

[Feltwell]

Thanks again everyone.

I've spoken to the surveyor on the phone tonight. The damp is in a small area of wall low down at the join between the external dining room (rear lounge) wall and kitchen wall - its the classic victorian/edwardian layout. He has said it is only a small area at the moment but should be treated to prevent it getting worse. He says these sort of brick DPCs can fail becasue water comes up through the mortar, but also said it could have been bridged eg by internal plaster (he says solid floors like the one in the kitchen, which has been covered with wood, do not always have any damp proofing). There is also a lean-to which has been built against the outside of these walls and I wondered if soem aspect of the construction of that could have bridged the original DPC. He said that is possible. But basically he didn't seem to know. HE did say that he didn't think a DPC on the scale required would cost much anyway. I am therefore tempted to forget about this until we haev moved, gradualyl pursue various options for trying to get rid of the source, and try an injected DPC down the line if all else fails. Does that sound sensible?

Yes. I'd be staggered if an injected DPC ended up being the fix though! That lean to sounds like a good place to start looking to me. If it's a small area it doesn't sound like much to worry about. Your surveyor is taking the standard modern approach - search the old posts on here, loads and loads about damp.

The woodworm is in a separate place, in the corner of the cellar, effectively in the front lounge's floor. He says it is in-extensive at the moment, but he says there was some dust around so if not active now, it has at least been active in the last couple of years. He thinks if it hasn't been sprayed we should get it sprayed ourselves - I'm going to get our solicitor to check this and for any existing guarantees. He did however say that it would be extremely difficult to find a house like this without this small level of woodworm - says he used to live on the same street and has been in a number of them. If there is no guarantee though, in the short term we are quite short of cash so it would help to leave a specialist survey (and possibly spray) until a later date. For a short survey and small area of woodworm spraying in a damp edwardian cellar, are we talking a couple of hundred quid or could we be talking thousands? If the former it isn't going to make any difference to the purchase so I'm tempted to leave it for a few months to a year until we are more stable financially. Again, is this a bad idea or foes it sound sensible?

Sounds sensible to me. If you really, really wanted to spray then it wouldn't cost much. A small area you could do yourself but if you wanted the piece of paper to show to future purchasers you'd need to get a contractor in. You could always get a quote now and use that as a bargaining tool. If you can get to the bottom of the floor from the cellar then it's a really quick and easy job.

But - to repeat what's been said earlier, search the woodworm posts on here, spraying is highly unlikely to be necessary.

Oh, and on the initial damp concern, he also said that it was possible the damp had spread to the timber underneath the original) suspended wood floor in the dining room, and recommended we get this checked out. Does anyone know how easy it is to do this sort of inspection and whether it could be done without pulling boards up? If its that simple I'd like to do it myself...

It's possible, and no you can't really tell without lifting boards and taking a look. Which way do the floorboards run, can you see them or if carpet is down even feel them through the carpet? The joists underneath run at 90 degrees to the boards, so you can tell if their ends are in the wall with the damp bit - which makes their deteriorating more likely but far from being a certainty - or in the adajacent wall. If the boards run parallel to the damp wall, the joist ends underneath are in that wall.

Does the floor noticeably dip at damp area? Is it very "bouncy" at the damp point? Either of those could indicate a problem, but I would expect the surveyor to spot those. Frankly if the floor feels solid enough underfoot and doesn't dip alarmingly or feel very springy then I wouldn't worry to much about it, if it does need work it's unlikely to be desperate and replacing a joist or two is disruptive but is not major work. Usually a repair is possible without replacing a complete joist, so all the floor doesn't need to come up.

What you've described there sounds fairly minor overall, it gives you a bargaining point to get the price down a bit but if the vendor won't move and everything else is right I certainly wouldn't let it put you off the house. You'll spend more on a new survey on another house I reckon!

 

[sidehaas]

Thanks Feltwell. It is a bare floor, the board run perpendicular to the affected wall so presumably the joists will be parallel to it. The surveyor did also say he thought there was also inadequate ventilation to that floor, withotu enough ventilation holes in the external walls, but didn't suggest how this could be improved. I'm not sure if its another side-effect of the lean-to. If there are no air-bricks, could I just drill a few holes in a brick above the level of the original blue brick DPC, or is this a recipe for disaster?!

 

[Feltwell]

Not at all. You don't just drill holes though, you take bricks out and install extra air bricks if required. It's not a hard job in a solid walled house (which I presume this is).

The surveyor is right, airflow under the floor is critical. Check for existing blocked air bricks first though.

If the joists aren't in that damp wall and the floor above looks and feels OK then I wouldn't let it trouble you too much, just get the airflow underneath sorted once you're in. It will wait until the spring!

 

[Keithj]

My understanding is that they don't directly measure 'damp' at all, they actually measure electrical conductivity. While this may be related to the amount of water in the wall it is also highly dependent upon the constitution of the wall, the level of salts etc. I presume this accounts for the 50% 'accuracy'.

It would be interesting to know the reading when the meter probes are dipped into pure de-ionised water. :wink:

Yes, it's effectively an ohmmeter, calibrated to give some indication of wetness or otherwise. My 50% accuracy figure is partly tongue-in-cheek, but not entirely. If you were to spread salt and vinegar on your wall, the meter would read "very damp". A dry salty wall indicates "dry". Dipped in demin water it reads nothing - the water doesn't conduct. Hold the prods between your fingers, and it will tell you whether you are a soggy person or a dry one.

But it does the job: I suppose a slightly damp piece of recycled marine oak would show wetter than a non-salty timber of the same wetness. I don't think that detracts from the usefulness of the device.

It proved quite adequate here: the timbers that shows "red" were indeed rotten. Those that showed "amber" were flaky on the outside but sound inside. Those that showed "green" were in good nick.

 

[Gareth Hughes]

My understanding is that they don't directly measure 'damp' at all, they actually measure electrical conductivity. While this may be related to the amount of water in the wall it is also highly dependent upon the constitution of the wall, the level of salts etc. I presume this accounts for the 50% 'accuracy'.

It would be interesting to know the reading when the meter probes are dipped into pure de-ionised water. :wink:

Yes, it's effectively an ohmmeter, calibrated to give some indication of wetness or otherwise. My 50% accuracy figure is partly tongue-in-cheek, but not entirely. If you were to spread salt and vinegar on your wall, the meter would read "very damp". A dry salty wall indicates "dry". Dipped in demin water it reads nothing - the water doesn't conduct. Hold the prods between your fingers, and it will tell you whether you are a soggy person or a dry one.

But it does the job: I suppose a slightly damp piece of recycled marine oak would show wetter than a non-salty timber of the same wetness. I don't think that detracts from the usefulness of the device.

It proved quite adequate here: the timbers that shows "red" were indeed rotten. Those that showed "amber" were flaky on the outside but sound inside. Those that showed "green" were in good nick.

Quite - the device measures moisture content of timber.
On a masonry wall it's frankly dangerous (says someone who's just ruined two families' Christmas by putting a stop to an exchange of contracts on a listed brick and flint house which was in the process of having its internal finishes hacked off to inject a DPC on the basis of a buyer's report which didn't suggest contacting the CO and asking if permission - or a less costly second opinion - might be needed before going ahead to ensure a sale. There's no visible evidence of damp, and even if there was, I suspect the leaking gutter, concrete back yard and masonry paint may be more significant contributory factors.)

 

[Moo]

Hurrah for Gareth!

 

[Flyfisher]

My 50% accuracy figure is partly tongue-in-cheek, but not entirely. If you were to spread salt and vinegar on your wall, the meter would read "very damp". A dry salty wall indicates "dry". Dipped in demin water it reads nothing - the water doesn't conduct. . . . . But it does the job:

I'd say that such meters do a job rather than the job . . . . which was precisely my point about ionised water: 100% 'damp' but no reading at all on the 'damp' meter.

I'm not trying to argue that such devices are useless, just that they need to be used with care and understanding. Gareth's story illustrates this perfectly.

It's much the same as any item of test equipment really; a dc voltmeter connected across mains wiring will read zero volts, but I wouldn't recommend it as a diagnosis that the wiring was safe to work on. :wink:

 

[Keithj]

Goes for any test equipment, really. You have to know what you're doing and how it works.
I have a workshop full of esoteric electronic test equipment, each item brilliant at what it does but potentially misleading for anyone who doesn't know the theory. Try an HF wavemeter on a VHF signal...

Wood usually provides the electrolyte needed, so wet wood, even wetted with demin water, will indicate "wet". The next question is where the wet came from and how long it's been there. It may, or may not, indicate that there's a damp and/or rot problem.

Hence 50%

 

[Matt Green]

Re: wood-boring insect activity

the charts below are shamelessly ripped from here:

http://www.ashgate.com/pdf/SamplePages/ashgate-practical-building-conservation-timber-samples.pdf

which looks like a very good reference book indeed. I had no rights to these images at all and they are posted for information only. I will remove them on request.

 

[Feltwell]

Matt, what do you recommend as the best brush-on furniture beetle insecticide?

I must do my cellar steps at some point - unpainted 1899 softwood, signs of frass so I think is active, but being in the cellar they will never be dry. Bottom of the steps are unsurprisingly the worst bit, a previous owner has already replaced the bottom 2 steps with breeze blocks so no longer any direct contact to the cellar floor.

 

[Matt Green]

TBH Feltwell, the amateur use products are all very much of a muchness. The insecticides used will be generic non-patented pyrethroids (usually) all of which are capable of killing furniture beetle larvae. Anything with Permethrin (or an active that ends in -thrin) will do the job well enough.

Even the brush on liquid sold by the consumer products wing of my current company. :shock:

 

[Feltwell]

Thanks Matt.