original victorian roof timbers-strengthening / infestation

[nik]

we would really appreciate any advice/comments - we have just had a building survey states roof structure "seriously defective"-origin report back which states that the roof structure is " seriously defective ".
The report states that the timber rafters are mainly original ( victorian roundish timbers ) and that the original roof coverings have been replaced with heavy concrete roof tiles and the roof structure itself has been poorly upgraded.
In addition , there ares signs of wood-boring insect attack in the main roof timbers- the surveyor could not state whether or not this was active.

could any of you please advise on the intial course of action?
we will need to know the extent of the problem repair costs prior to deciding on proceeding with a sale/negoitate price.


if we had a woodworm contractor inspect for any active woodworm , would they also be able to advise on the structural integrity of the roof timbers in relation to any damage caused by woodboring insects and any strengthening action to be taken in respect to this AND the structural effectiveness in relation to the roof timbers handling the roof coverings?
Or would it be a roofer or builder who would be able to advise on this?

we are thinking that first port of call would be to assess if wood-boring insect is a) active, b)asses the extent of any structural damage to timbers due to infestation- Is this the correct thing to do first ? we are checking with solicitor to see if guarantee in place.

would we then need a roofer or builder?- to assess if the roof timbers are adequate to support the heavy concrete tiles, and advise if any strengthening is needed.


And lastly, would the works to replace the original roof coverings have needed planning permission and or building reg sign off? And if so would the suitablility of the original roof timbers have been assessed to see if they could support the replacement tiles?
The property is in a conservation area if that information helps at all?


many thanks in advance of your help
befuddled Nik :?

 

[Lime]

The problem you have is the inappropriate use of heavy tiles.
I presume the old roof was slate.
It is common for old tiles to be taken off (..you won't want them old tiles put back on, will ya guvna? .... the old tiles then get taken off and sold at upto £3+ each)
It's also common for cement tiles to replace slate.
Unfortunately the roof structure, although perfectly adequate for slate, is not strong enough for cement tiles particularly when they get wet.
The roof may collapse anytime.

If you are buying the property (or have bought it) you need to have the tiles removed and reroofed with slate.

I'd worry about the woodworm when you are having the tiles replaced.

 

[nik]

you need to have the tiles removed and reroofed with slate.

thought you might say that
The property is a semi detached ( next door has the same tiles) the extension has the same type of tiles.
whats the score with conservation areas ? i would have thought replacing with slate would be getting the property back to how it would have been originally. But it will then look very different from adjoining property and the newer extension.
It seems to me that conservation officers are concerned about the look of the exterior property.
So do you think they would approve of returning to slate or oppose it?

if they oppose return to slate tiles , can the roof be stengthened from inside without taking whole roof off and starting again?
excuse if a silly question, not knowledgable about roofs

 

[JoceAndChris]

Poor nik, what a can of worms!

I'm not knowledgable about rooves either, but I am very chilled out about woodworm.

Woodworm protection seems like the next biggest scam after damp proof coursing. Our first mortgage application (which went pear shaped) involved the mortgage company saying they'd withhold a couple of thousand until we had the whole house treated. This was because the surveyor had found an old infestation.

We came very close to arranging expensive and potentially damaging treatment.

Fortunately the mortgage company who did eventually agree to lend us the money were not so OCD about woodworm. Good, because there's no live woodworm here. Have a good look round your property, everywhere you can access, and look for "frass", or minute little patches of sawdust on the surface of the wood. That will tell you if the infestation is live. Don't trust anyone else with this task, especially if they have a vested interest in getting tyou to pay for expensive treatment.

Also, I'm amazed at the strength of my woodwormy roof supporting timbers. The timbers are completely riddled with holes, but still hold up the slate roof. And the floors hold up too.

But it sounds like the timbers are being asked to do too much where you are.

You should call the council about the whole conservation area thing and the roof- different areas have different levels of strictness.

 

[Feltwell]

The impact of the house being in a Conservation area depends on if the roof was done before it was a conservation area, or afterwards. If done afterwards and without permission then you could have a major problem. This is something that your solicitor could check.

Concrete tiles replacing lighter originals is not uncommon, I had the same problem with a 1920's house. In my case making a temporary hole in the side of the roof and passing new purlins in, and then bracing them off a central wall plate, was enough - no more than £800 and 2 days of work. But it depends on how bad yours is. My roof had stood lke that for 30 years and was in no danger of collapse, but it was showing some signs of deflection.

I'd say get a roofer in to have a look, preferably one that comes recommended by someone. The terminology used in surveys tends to scare people but it's not always that major a problem.

Re. woodworm - I think you'll struggle to find a Victorian house that hasn't had woodworm at some point in it's life! It may have already been treated - ask for evidence from the seller. All a woodworm contractor will tell you is that they can spray it and offer a 30 year guarentee, which does nothing if the woodworm isn't active. If you've had a full structural survey then they should be able to tell you if it's active - have you called your surveyor? Many will tell you over the phone but not in writing. Woodworm treatment ranks alongside damp proofing as one of the biggest wastes of money going. Timbers can be quite heavily infested and still structurally sound. Looking for frass as Joce says is a good sign as to if the woodworm is still active.

Woodworm is a generic term though - ask your surveyor if it's furniture beetle or something more serious. Again last time I had a survey they would only say "signs of infestation" in writing, but on the phone were quite happy to tell me that it was furntiture beetle and did not show any signs of being active.

I've just replaced my roof - my house is not in a conservation area, I didn't need planning permission. I did need building regs, but that is a fairly recent change and more to do with insulation values than anything else. Chances are that yours needed neither if it was done some time ago.

Hope this helps.

 

[another_richard]

Not sure if you mentioned it but is the apex running from front to back or across the middle?

Either way it is possible the weight of the concrete tiles will be pushing the exterior walls out.

As already stated remove the concrete tiles, felt and replace with slate.

Also, consider A-framing the inside for extra strength.

 

[Lime]

can the roof be stengthened from inside without taking whole roof off and starting again?

With difficulty and no certainty either.
Unlike new roof timbers which are constructed as a whole in the form of a truss old roofs were put together on the building.
Old roof structures vary but many victorian roofs only had rafters, a rudimentary ridge beam, the ends of the rafters nailed into the wall plates and small ceiling joists holding them together.
In many roofs there were no purlins and the wall plates sat on the top of the walls with no other fixing apart from the small nailed joists.
The main lateral strength was obtained by the battens that the slates were nailed on to.


The problem with attempting to reinforce an old roof is that, unless the tiles are removed, it is not possible to tell if the structure is still sound albeit inadequate.
The rafters will be undersized to take any extra load from the tiles anyway.
Installing roof timbers that are the width or length of the house is another difficulty.
Affixing the extra timber will disturb the roof too and may cause collapse.

 

[JoceAndChris]

Feltwell you're completely brilliant and a mine of useful info but I don't agree with you that a full survey can reveal if woodworm is active or not. That can only be done by the householder and involves a bit of invasive checking - ie lifting floorboards, a job that requires a very slow and delicate touch if you aren't to damage them.

Our surveyor didn't even crawl in our roofspace. We did though, and found no frass, although he'd recommended we get the timbers re-treated.

 

[Feltwell]

Feltwell you're completely brilliant

Ahh, thank you, you're fantastic too and clearly such a good judge of character. I shall fit French doors to my house now to get my head through !!! :lol:

Seriously, you're quite right, like everyone else a surveyor can only check what he can see, which won't include hidden spaces. Some will go into all accessible places though - in my house up in the attic there is a little door that you can crawl through and then crawl right round the eaves of the house, which is exactly what my surveyor did.

Back to the original post - I wouldn't write off roof strengthening what's already there until you get someone knowledgeable in to take a look. It could be whole new roof job, or it may just be minor strengthening works as I described above. That's all I did to my old house, and it passed a full structural survey when I sold it with no problems. Inserting purlins looks scary but can be relatively simple. It all needs checking out though, as you have a huge range of potential costs here - a few hundred pounts for minor strengthening up to tens of thousands for a complete roof re-build, depending on the size and accessibility of your roof.

 

[Matt Green]

Feltwell you're completely brilliant and a mine of useful info but I don't agree with you that a full survey can reveal if woodworm is active or not. That can only be done by the householder and involves a bit of invasive checking - ie lifting floorboards, a job that requires a very slow and delicate touch if you aren't to damage them.

There are professionals that can tell you if an infestation is active or not without trying to sell you anything. I've heard that some of them are even quite good at it.

Forgive me if I put the horse before the cart here for a moment, but i'm going to try some science:

Is the roof felted?
Is it insulated?
Do you pictures of the damage, original poster?
Did the surveyor just see some holes and run for a caveat or did he use a resistance meter the way it's supposed to be used in the roof timbers and get moisture content value for them?

The reasons behind the questions are that furniture beetle (and i'll assume that's what is leaving exit holes in the roof timbers) need the timbers they inhabit to have a moisture content above about 15% ideally a little higher. A lack of felting and insulation will lower the temperature in the roof and raise the relative humidity of the air in the roof void. The moisture content of the roof timbers will rise with %RH to a max of about 23% at 20C, higher at lower tempertaures, which is enough for furniture beetle to start attacking the outer, sapwood parts, of roof timbers. What proportion of the timbers are sapwood varies from roof to roof.

Before anyone starts sloshing chemicals around, get a structural opinion and clean the roof out thoroughly. Reassess the situation the following year and look for fresh emmergance holes. Fill any old holes with wax if it's not too massive a task, it's quite a fast way of filling them. Or limewash the timbers: something that provides a baseline for comparison later on. Your roof is unlikely to collapse soley because of furniture beetle damge, I'd suggest sorting the important stuff out first.


Matt

 

[JoceAndChris]

There are professionals that can tell you if an infestation is active or not without trying to sell you anything. I've heard that some of them are even quite good at it.

Matt

No offence intended Matt. If I'd had a research entomologist, as you are, around to help it would have saved a lot of heartache.

 

[chuckey]

Both my house and my (attached) neighbours house and a friends house (three doors away) were re-tiled using concrete interlocking tiles in the late 70s. All three houses have suffered the same effect whereby the rafters slid of the wallplate a small amount, causing the roof to belly slightly. On my house it resulted in the soffit being about 1/2" displaced in the centre of a 20' run. My friends house has a hipped roof and it was bellying rather more so his solution was to simply to bracket the rafters to the ceiling joists in one direction and to put in some wooden (4" X 2") ties right across the roof in the other direction. My house's soffits has not moved for 20 years (cos' that when they were replaced with tightly fitting plastic ones).
I would get the surveyor to be more specific with his critiscisms, and invite him to suggest what you should do about it. I had to attend to the houses wood worm when I moved in (morgage co's requirement). Used a "professional" for the houses interior, did the loft myself. I found out later from my aged neighbour that the woodworm appeared after Southampton docks were bombed in 1941!! In retrospect, I don't think it was active, but it was difficult to argue with the mortgage co. at the time.
Frank

 

[AMc]

My GUESS would be that the worm dates from the previous leaky roof. That re-tiling in concrete made it water tight and the infestation died out as the roof dried - BUT that's only a GUESS.

I wouldn't be unduly worried about the worm but I would be worried about the heavy roof. My house was retiled in concrete in the 70's but thankfully the original builders built the roof so heavily that there is no deflection. Reslating the entire house will be expensive and intrusive and unless your new neighbours want to do the same thing it will probably make both your houses look a bit odd.

If you want to negotiate the price down then I would look for a written estimate from a local roofing company to retile the entire roof in new slate and replace/splice all the worm damaged timber. That should get you a large, solid number for the worst case.

If you buy the house then I would instruct a structural engineer to look at the timber and recommend the bracing work you would need to support the existing roof then get a couple of local builders/roofing companies to quote based on the engineers report.

Then I would go about assessing if the wood worm is actually active by the methods described by others. You will have to try very hard to find new structural timber that hasn't already been kiln dried making it inhospitable to insects and tanilised with insecticide too, so the risk of the old timber infecting the new is pretty slim IMHO.

I add the caveat that my builder sprayed the roof timber in my house 'as a matter of course', by the time I realised what was going on the 'damage' (if there is any) was done. The main house was sprayed about 15 years ago so nothing I could do about that. It may be unnecessary but I don't spend any time in the loft so I try not to worry about it.

 

[nik]

I wouldn't write off roof strengthening what's already there until you get someone knowledgeable in to take a look. It could be whole new roof job, or it may just be minor strengthening works as I described above.

update- had three roofers round, two we instructed that are familiar with old properties and one the vendor instructed.
good news is that they all agreed with the work needed and the that surveyors report was ot and the timbers are in good condition and " its a good roof" roof is not "seriously defective" afterall. And there is no sign of active insect infestation, but we will get its sprayed.

One thing that was a complete mystery to all three roofers was the " wet rot on the end roof timbers".. they couldnt work out what the surveyor meant by end roof timbers, as apparently its not a roofing term!!! the only thing they could find was wet rot to the facia of the outside toilet :lol:
some minor strengthening is required, and repair to valley , estimate of £1k .. so thankfully we dont need to walk away
thanks for your help and i look forward to posting and sharing in the future as we start to return some of the charm and soul to this little semi vicorain labourers cottage

 

[biffvernon]

And there is no sign of active insect infestation, but we will get its sprayed.

NO, No, No!

If there is no sign of active infestation (and this time of year is bang on the active season) then don't go sloshing poison about. It will do no good and only harm.

Take Matt's advice when he said "Reassess the situation the following year ". He's saying don't act in haste.

 

[nik]

.. i meant at a later date if needed , after inspection