Painting/treating roof trusses?

[chippy1]

re: protecting the wood against wood-decaying fungi and insects, mould etc....

Hi All,

Thankyou for all the help I get from this site....first time period property owner (original parts of house go back to 1600s) so appreciate all comments.

Can anyone recommend the correct paint/treatment to use on original oak roof trusses/beams in loft?

Some of the original trusses are made out of what looks like Oak trees (trunks) cut to size and are naturally uneven shapes. I do have a cert(Guarantee) that shows all timbers/beams/trusses were treated in 2004 against wood boring insects/wood-rotting fungi but didnt know if, after 15years, if it would be useful to retreat the loft timbers? I've always lived in "newer" properties so wasnt use to seeing lots of different shapes and sizes used for roof trusses but guess the property has been here for 300-400years so they must be doing the job!

Can you mess around too much with these things or is it good to give the roof trusses a general maintenance now and again to keep them protected?

If so, please could something advise me on the best thing to buy to treat the timbers?

As a side note....I have noticed a couple of historical splits in the wood on some of the trusses....is it possible to keep the original trusses in place but strengthen them by screwing new timber to to the old trusses? Most look in good condition but would feel better adding alittle strength/support to 1 or 2 of them....

thank you for any help

 

[Flyfisher]

You’ve already made one important observation - that the roof is still standing after a few hundred years, which is not entirely surprising if it is made of oak. Modern roof timbers are graded softwoods and require chemical treatment for longevity, but even so I doubt many will survive 400 years as yours has. Our main roof dates from around 1550, is similarly constructed with oak and looks, to my amateur eye, highly over-engineered compared to a modern roof - and therein lies the reason for its survival. Even though the softwood pantile battens were in poor condition, leading to many slipped tiles and resulting leaks, the structural roof timbers were only affected in a few places where water had pooled, notably in a couple of A-frame joints. Otherwise, the draughty roofspace had kept the timbers well ventilated and therefore mostly dry, thus protecting them. As far as I know, the only treatment has been to limewash the timbers, though I don’t know how protective this is and suspect it was mainly for decoration. I may re-limewash them but otherwise have no plans for any chemical treatment.

As for repairs/strengthening, it’s almost impossible to advise without seeing the timbers in question. Perhaps you could post some photos? Splits (or ‘shakes’) are not uncommon and if the timbers are typically over-sized then may not be anything to worry about. As you’ve noted, the roof is already a few hundred years old and such splits are most likely during the first 50 years or so as the wood dries out and reaches equilibrium, so unless you have good reason to suspect a problem it’s likely those splits have been present for a few hundred years without causing problems. But again, difficult to be definitive without some photos.

 

[chippy1]

You’ve already made one important observation - that the roof is still standing after a few hundred years, which is not entirely surprising if it is made of oak. Modern roof timbers are graded softwoods and require chemical treatment for longevity, but even so I doubt many will survive 400 years as yours has. Our main roof dates from around 1550, is similarly constructed with oak and looks, to my amateur eye, highly over-engineered compared to a modern roof - and therein lies the reason for its survival. Even though the softwood pantile battens were in poor condition, leading to many slipped tiles and resulting leaks, the structural roof timbers were only affected in a few places where water had pooled, notably in a couple of A-frame joints. Otherwise, the draughty roofspace had kept the timbers well ventilated and therefore mostly dry, thus protecting them. As far as I know, the only treatment has been to limewash the timbers, though I don’t know how protective this is and suspect it was mainly for decoration. I may re-limewash them but otherwise have no plans for any chemical treatment.

As for repairs/strengthening, it’s almost impossible to advise without seeing the timbers in question. Perhaps you could post some photos? Splits (or ‘shakes’) are not uncommon and if the timbers are typically over-sized then may not be anything to worry about. As you’ve noted, the roof is already a few hundred years old and such splits are most likely during the first 50 years or so as the wood dries out and reaches equilibrium, so unless you have good reason to suspect a problem it’s likely those splits have been present for a few hundred years without causing problems. But again, difficult to be definitive without some photos.

Thanks Flyfisher....appreciate the very helpful reply.

I have recently had to get a roofer to repair the roof ridge as there was so much daylight coming in from the top of the roof you could almost put your hand in the loft space when sitting on the top of the roof. Since closing off all the gaps on the ridge, I did notice one truss had a new split, maybe less ventilation is getting into to loft space or it had rain damage that was able to dry out once the roof had been repaired. I know what you mean about the old roofs constructed with Oak...it almost looks like someone has cut off old branches from a local oak tree and just thrown it up on the roof....amazing how they use to do it but when you are so use to seeing straight cuts and right angles in modern roof structures, its alittle scary!

Would it cause any harm to sister a 2x4 (or 2x6) to repair the damaged truss?

thankyou again for all your help

 

[TheForge]

I would look at it like this, the trusses have survived 400 plus years with likely little intervention. They’ve survived perfectly well without the addition of any modern chemicals. As Flyfisher says, if they were decorated historically it would have been with limewash. If they haven’t been decorated why wouldn’t you leave it like that?

The roof is likely in happy equilibrium and unless there are obvious defects I would leave it well alone. In terms in any shakes a photo would be useful, but unless there is evidence of recent worsening, I wouldn’t be concerned.

I assume given the age of the house it’s listed? In which case any amendments may require LBC.

A specialist conservation surveyor or engineer could be employed to put your mind at rest by surveying the condition.

 

[Abi Cott]

If it's dry up there and there is a bit of a breeze I'd leave well alone. Insects like damp wood. 400 year old dry oak is unlikely to attract their attention and is a total waste of money spraying it.

I had a few issues in my loft when I moved in due to a previous owner adding a liner that wasn't breathable which made the attic distinctly muggy, insect heaven, but fortunately they hadn't found it yet. It's now got a bit more ventilation and I'm happy it will go on another 200 years, and that's with mainly pitch pine timbers as mine is quite a bit younger than yours.

 

[88v8]

Would it cause any harm to sister a 2x4 (or 2x6) to repair the damaged truss?

If there's no active woodworm, don't worry about it. Woodworm is only active in damp timber. Is it damp? No? Then don't worry about it.

As regards splits, a longitudinal split does not weaken the joist.

Regarding wonkiness, the roof of our 400yo cottage was made of odd bits of hazel trunks. About 3" diameter, but of course they taper. One of them had collapsed at some time in the last 200 years, due to woodworm.
I sprayed all the timbers with Cuprinol 5-Star, then I repaired the collapsed rafter with another hazel trunk that I cut from the garden. Fortunately I was able to find one that had a similar curve.

Keep calm and let the roof carry on.

Ivor

 

[chippy1]

Thanks all....appreciate all the replies! I guess the trick is to stop looking at these old properties with "modern" eyes.....the important thing is to work with them not against them.

There have been conservation/planning officers that advised to close off large gaps (property was originally built without soffits or fascias) and put in vents to help the loft to breath, which seems to go against "leaving" these old properties as they are. It's not had soffits/fascias for 300-400 years so why advise to add them?

I would have thought the more ventilation the better for these old lofts and most importantly not to change the outward look of them...sadly, you seem to get a different answer depending on what planning officer you speak too... As I didnt want to change how the roof line looks (its never had soffits/fascias since the day it was built) from the outside and keep it looking original as possible, I just ended up using a very small amount on expanding foam inside (where the soffit would normally go) to give alittle extra insulation but left enough gaps so I still get plenty of airflow.

This meant no changes to the property and kept the powers-at-be happy! Its so hard to know the best thing to do when you get different advise from different official departments....thats why its good to find forum like this, where I can get 2nd or 3rd opinions on things before even thinking about making any changes.


thanks again all...appreciate the help!

 

[MatthewC]

If you have a "cold" roof space then you want lots of ventilation, and you should lay a foot or so natural insulation (e.g. sheepswool) on the rafters/ceilings of the floor below. Just block up the gaps enough to stop birds nesting (although you could encourage owls?). Your upstairs will become nice and toasty - the impact on my house was immediate.

You don't want to talk to planning officers really as they might have no idea at all about an old property and so they give you duff advice (albeit possibly good advice for a modern house)! A conservation officer should have a better idea though - I can't really believe a CO would suggest adding fascias.

NB I understand that woodworm needs 14% moisture content to survive - but I'm less sure on other insects such as DWB - so simply aerating the loft space will kill the woodworm at least. All that will be left are lots of holes and a few dead beetles!

 

[chippy1]

If you have a "cold" roof space then you want lots of ventilation, and you should lay a foot or so natural insulation (e.g. sheepswool) on the rafters/ceilings of the floor below. Just block up the gaps enough to stop birds nesting (although you could encourage owls?). Your upstairs will become nice and toasty - the impact on my house was immediate.

You don't want to talk to planning officers really as they might have no idea at all about an old property and so they give you duff advice (albeit possibly good advice for a modern house)! A conservation officer should have a better idea though - I can't really believe a CO would suggest adding fascias.

NB I understand that woodworm needs 14% moisture content to survive - but I'm less sure on other insects such as DWB - so simply aerating the loft space will kill the woodworm at least. All that will be left are lots of holes and a few dead beetles!

Thanks MatthewC...yes, you are right...local planning officer advised on fascias, I ended up not doing any of the work so didnt need to take it any further. As a rule "expanding foam isnt the best way to insulate a loft space but as I wasnt using it on the under side of the roof and it was just a small amount to stop birds etc getting in and nesting, I went with that option and made sure I left enough gaps for airflow. In some areas I had a 10-20cm gap where soffits would normally be fitted and In those areas where I did use the foam to close that gap, I'm able to drill small holes in the foam at regular intervals, big enough for strips of overflow pipe to be inserted so it still allowed enough airflow to keep the loft space cool...I didnt want to make any part of the loft "airtight" and inserting 22mm overflow pipe at regular spaces meant fresh air could still pass through and ventilate the loft but the bigger gaps where closed off...cheap and doesnt change the look of the property and no structural changes....so everyone happy!

The only issue I have had is when I repaired the ridge of the roof and a couple of the 300-400yr old oak roof trusses must have had water damage and since the repair they've had chance to dry out and split, so didnt know if ok to "sister" a couple of 2x4's to give added support?

This thread has been really helpful and I learn something every time I come on the forum! ...thanks again everyone!

 

[TheForge]

We really need a photo of these splits in the timbers to advise.

 

[chippy1]

We really need a photo of these splits in the timbers to advise.

thanks....will try to post some pics this week...

 

[chippy1]

We really need a photo of these splits in the timbers to advise.

Hi Forge.......I just went up in loft after replying and took some pics and trying to add the file (attachments) but keep getting error message saying "file too large" but all I've done is take a photo from my phone and saved to my pc to copy onto this message???

Any ideas how to post a standard photo?

thanks

 

[LadyArowana]

Any ideas how to post a standard photo?

thanks

Most pix are too big for the site now, so the work around is to use a photo hosting service and then link to it

 

[chippy1]

Any ideas how to post a standard photo?

thanks

Most pix are too big for the site now, so the work around is to use a photo hosting service and then link to it

Thanks LadyArowana....was starting to think it was me!

 

[Flyfisher]

Reducing the size to around 800 pixels wide usually works for me.

 

[chippy1]

Reducing the size to around 800 pixels wide usually works for me.

Thanks Flyfisher...tried reducing to 800, then 700....and got it to work at 400 pixels!

Hopefully pics now work!...thanks again!

To all,

Would appreciate any advise on whether these trusses need some TLC or alittle extra support (sister 2x4's either side?) or is this just natural wear/weathering and not to worry about?

thanks again

 

[TheForge]

A few observations from the photos:

- The felt above the timber looks to be a non breathable type which may cause condensation and promote decay.
Is that old or a recent addition?

- There is evidence of cuboidal cracking on all images suggesting some shrinking possibly linked to rot, either current or past. If you push a bradawl or similar in to the timber is it soft?

- The last image looks like the timber has been charred by fire.

 

[chippy1]

A few observations from the photos:

- The felt above the timber looks to be a non breathable type which may cause condensation and promote decay.
Is that old or a recent addition?

- There is evidence of cuboidal cracking on all images suggesting some shrinking possibly linked to rot, either current or past. If you push a bradawl or similar in to the timber is it soft?

- The last image looks like the timber has been charred by fire.

Hi TheFroge...thanks for your reply.

The felt is a very old addition and no updating of roof has been done during the past 3 or 4 owners of the property. I have been in the property a couple of years now and havent noticed any condensation as there seems to be plenty of airflow in the loft space. Even going up to take pictures, I noticed the drop in temp between the bedrooms and climbing up into the loft. So the airflow is making is alot cooler and no damp smells. There has not been any fire and most of the trusses are alot lighter in colour, they are like concrete to nail into and are very solid, most dont look the same as this one. I have recently made repairs to the ridge of the roof as there was alot of gaps for the rain to get in so one or two of the trusses could have rain damage over time...the cracking in photo 1 might be where the truss has been allowed to "dry out" after these roof repairs had been made.

Most of the trusses are looking fine (for a 300-400yr old house) and I'm sure it helps being a mid terrace property but I wasnt sure if I should/could leave these trusses as they are or giving them some extra support might give a bit extra peace of mind...??

thanks again

 

[Kearn]

Third pic immediately looks like charring to me too... colour and texture. Do any of the other roof timbers have a similar appearance?

 

[chippy1]

Third pic immediately looks like charring to me too... colour and texture. Do any of the other roof timbers have a similar appearance?

Hi Kaern,

thanks for your reply.

Not from what I can see...Most of the timbers are a light bown colour and look "normal"...if that makes sense!? My neighbour has been living next door for over 40years and nothing like that has happened and no sign of there ever being a fire on the felt/brickwork around the timbers.

I was thinking it was "historical rot" where the truss had been open to the elements for many years and have since dried out? Most are very old original, solid oak beams...I took photos of the 2 worst timbers as hoping I could get advise on replacement/strengthen/treat???

I can get a carpenter/joiner to cut some new beams to help strengthen the timber in the photos but new to all this so wasnt sure what best option would be?


thanks again