Restoring the appearance of the exterior of our cottage

[sevenleaf]

Following from the excellent advice from Helen Foster, plasticpigeon, 88v8 (Ivor) and FlyFisher regarding laying our floor tiles, I was hoping to again draw on the collective knowledge of the forum for approval and ideas of how to proceed with finishing and weatherproofing the outside of our timber framed cottage that had seen better days when we purchased it.

We have nearly finished removing the plastic paint that was covering the limewash - which had all failed in places, blown/spalled some bricks and had left the wall in a very patchy and messy state. Some parts of the wall were rebuilt completely when we had the place underpinned, failed bricks were replaced and failed joints were re-pointed.

Now we are looking for advice with how best to:

1. Protect and enhance the exposed (and vunerable) oak timbers. These look to have been covered with a very hard substance in the past (probably the rock-hard cement used in abundance elsewhere), which has mainly failed and fallen off. This will pick off without causing any damage to the oak underneath. I'd like to retain/renew the black appearance and protect the oak (which is as soft as cork in some places) from the elements. Should I scrape this back to good - pictutre 2?

2. Create a 'lip' to prevent water from water working its way under the oak timbers. You can see where a previous attempt has failed and come away. I have had two suggestions - a lead trim (not keen, concerned of water ingress behind/underneath) and a new shallow lip up to the wood, similar to before however with a lime-based mix this time - limewashed over.

3. Finishing the surface of the wall. All of the white is limewash and we are very keen to continue this. Most of the loose has been raked back to good already, the rest will be done prior to any further work. Some repointing has been carried out although not to an amazing standard. One concern is how well further limewashing will fit in with the existing, however we would prefer any patchiness to the alternative of removing all existing back to brick and starting from scratch - as showing the progressoin of the property is part of its charm to us.

 

[Zebra]

I would think that a lead trim would be an excellent way of protecting any exposed lip of timber or of render. What other alternatives are you thinking of?

 

[Flyfisher]

"Protect and enhance the exposed (and vunerable) oak timbers."

Why do you think they are vulnerable? Many of our oak timbers have been exposed for hundreds of years and although a bit 'gnarly' they remain rock hard. My amateur feeling is that as long as they can dry out after rain then they are not very 'vulnerable' at all. Of course, if some of them are positioned such that water can pool on or under them or be otherwise trapped then I'd agree they may be vulnerable (and we've had our share of decayed sole plates damaged by water trapped behind cement render), but I wouldn't worry too much by them simply being exposed to the elements.

From your post it seems like you're doing all the right things; i.e. removing cement and modern paints and replacing with lime and limewash. It was not unusual to limewash over oak beams so perhaps the easiest and quickest approach (once all cement and modern paint has been removed) might be to simply limewash over the walls and timbers, though I appreciate some people prefer to emphasis the oak by leaving it bare. Check out the Lavenham Guildhall for a stunning example of this approach.

As for a lip for the 'plinth', lead flashing would be ideal though might be difficult to effectively retrofit. Perhaps the joint between the oak sole plate and plinth could be raked out and the lead flashing inserted underneath the plate, but I agree that care would be required to ensure water would not pool on the lead and seep underneath the plate. Cutting an angle on the plinth to slope the lead would mostly avoid this, though there's still a risk of wind blown rain getting underneath if the pointing above the lead fails.

Perhaps a simple angled 'fillet' of lime mortar would be adequate. It should certainly allow any water to dry out, thus protecting the plate.

As for the walls, I agree with your approach to use limewash, though I'm only too aware of how difficult it can be to remove all the previous coverings as we've done something very similar - basically removing all the loose stuff and repointing with lime, but where patches of previous paint remain firmly attacked we've just left it if it would be more damaging to the wall to try and remove it. If it does eventually flake off in the future then that's fine and it will be easily patched up with another coat of limewash.

If you have problems with limewash adhering to areas of modern paint then you may wish to investigate this 'pozilime' formulation from Ingilby paints: http://www.ingilby.co.uk/pozilime.html

 

[lucyl123]

Do you think it is the hard covering that was previously on the oak timber framing that was allowing damp to enter the wood? It might be worth checking to see why this area is so vulnerable, as FlyFisher commented - is water draining incorrectly from a gutter or downpipe?
There's no point in carrying on with your repair works if there's an underlying problem which will cause your oak timber to get damp frequently. A chemical treatment for the wood will only help to solve the current damp, and will not prevent further damage.

As a general rule, try not to take a destructive approach, picking at the oak timber until there's not much left - this reminds me of the building practice of 'defrassing' where the contractor would simply slice off the affected damp/damaged timber layers. This can be dangerous if the oak timber framing is weight bearing or might threaten the structural integrity.

One of the repair methods I've seen on some older heritage buildings is the metal strap - probably would need to be made by a blacksmith. I wouldn't say that these are the most attractive option, for a lovely old cottage, but it does hold together any rotting timber and the process is reversible (as in you can remove the metal strap at any point) might be good if you are in a rush or want a repair solution over a bad weather period.

For proper, long-term repairs you'll probably need the help of a carpenter who will cut out the rotted timber and will know how to scarf in new bits of oak framed timber using traditional jointing methods.

Although it might seem like a lot of work and stress for you at the moment, it is worth remembering the history behind the building material, I think oak timber framed buildings are beautiful and well worth all of the effort. There are some interesting facts about it here: https://www.ernestbarnesltd.co.uk/7-facts-oak-timber-framing-didnt-know/

 

[DavidB]

Hi sevenleaf

On the really poor exposed beams you could consider cutting out the rot and then splice in a new piece i.e. reface. This means you don't have to cut out all the beam / sill.

I have seen lead used (both pushed under or in some examples over a sill) and then folded down to create a fast draining lip. It can look passable, but I personally don't think it looks great. There are several examples in my local village.

 

[88v8]

I have read somewhere that lead in direct contact with oak is a no-no, because the tannic acid will degrade the lead. The suggested solution Iirc was to interpose a layer of building paper.
As to it not looking that good, well it was a period bodge.

I have mixed feelings about leaving oak to fend for itself. There is a reason that houses were rendered over, often the timbers had rotted especially at the joints. Also where the grain is adverse, that is it leans back into the timber. There are examples in our cottage. And then they were painted to hide the repairs. Do spliced/repaired timbers look good? Hmmm.
And will the bare repairs rot in time? You bet.
The sole plate is an added problem as it may be under attack from that non-existent cause, rising damp, and in that case the only solution is to interpose a dpc even if it is as humble as a layer of felt or overlapped slates beneath the sole.

As to the timbers, I am currently addressing a couple of external lintels. I have burned off the household black paint with a heat gun & wire brush, and removed the putty with which most of the grain had been filled. After some more moderate puttying to fill nail holes and adverse grain, I treated with a 50/50 of boiled linseed oil and turpentine. It soaks in. Then a coat of linseed black paint, then another. I might start another thread.

I think I shall carry this approach into the timber frame, which is likewisely coated with household black and under which I see evidence of old fillings.
Old fillings. My dentist mumbles about those.

Ivor

 

[Flyfisher]

I have read somewhere that lead in direct contact with oak is a no-no, because the tannic acid will degrade the lead.

Yes, for new oak but isn't the tannic acid gradually leached out over the first 50-100 years or so, therefore this might not be so important for repair works? Not sure really.

I have mixed feelings about leaving oak to fend for itself.

I'd say it needs some help to ensure its potential durability is not compromised by things such as trapped damp, but where it is well positioned with good ventilation it seems to do a pretty good job of fending for itself - as hundreds of 500 year old, oak-framed period properties clearly testify. Of course, such properties are self-selecting as all the inferior and poorly built ones have indeed rotted away, but there are plenty remaining to prove the potential longevity of oak. I've no idea about the upper limit to that longevity though.

 

[DJH]

Lead? Lead? Did someone mention lead?
Oak and lead don't get on very well especially in warm moist unventilated conditions. As a belt and braces approach if you were to fit a flashing under oak a good thick coat of a spirit based hard bitumen paint applied to the lead where it comes into contact with the oak will do the trick...