Mind the gap

[DavidB]

Hi

I have a late 1700s timber-frame cottage which has an external render applied to an expanded metal lath (EML). Since I've owned the house there has been a crack on the rear of the building. It opens up as the weather improves! I suspect that either the EML has become detached from the stud work or the render has become detached from the EML. The actual frame (which is exposed on the inside is relatively ok. i.e. it has suffered some movement over the years but there is no signs of movement inside since recent decoration. So what I mean by this is the crack has been filled and has opened up on the exterior, but the interior decoration does not show any new gaps - so I don't think the frame itself is increasingly bowing outward.

There is another problem related to this which is the window frame in the same wall. It shows signs of movement and a gap has developed between the frame and the internal casement/finishing panels. I actually spoke to the guy who installed these windows, he grew up two doors down and ended up being a carpenter, he's now in his 80s and thinks he put these in around the 1970s - so I didn't push the question of warranty

I am tempted to hack off the render around the crack and try to get back to the EML and effect some kind of repair i.e. a patch repair of EML nailed to the frame and then re-plaster. With regards to the window - I was thinking of taking off the internal finishing boards and checking or adding some mechanical fixing from the timber frame to the window frame i.e. a straps/bolts or whatever I can fit in and then re-install the finishing panels so the gap is no longer visible. Alternatively, I might have to end up taking the frame out and then re-fixing it completely.

Some might call this a bodge - I was thinking it was more minimal intervention... has anyone had a similar problem and what did they do and what do you think I might have to think about with this problem?

I have attached two pictures to help clarify what the heck I'm on about. Thanks for your replies....

 

[Penners]

As you have first-hand evidence of the cracked rendering moving in warmer weather, you obviously know that it still moves. I think it's possible (but by no means certain) that the EML may not have been effectively fixed to the timber frame underneath, thus in warmer weather the metal expands and the crack opens up. So you may find that hacking off the render (which, if it's concrete - which it probably is - is likely to pull some EML off with it), resecuring the EML (a new piece if necessary) to the timber frame and re-rendering could resolve the problem.

As regards the window, do you have any evidence as to whether it is still on the move? Could it have moved at some point in the past and now be stable again? If the latter, then you might be able just to fill the gap and leave it like that. You mention "adding some mechanical fixing from the timber frame to the window frame" but surely such fixings must exist already, mustn't they? How else would the window have been fixed in the 1970s? I don't think adhesive fixing of window frames existed in those days. However, if you're in any doubt, the old boy up the road might be able to remember.

 

[middi]

The reality is that old timber frame cottages have not the ideal framework to sustain rigid (or soft, ie- lime render) complete exterior coverings, they would have been rendered externally between studs, or, been completely covered with lap boards ( usually painted black ). Some later cottages lath and lime plaster externally.
The reason why external render ( especially the rigid kind on eml) is not suitable is because these cootages are always on the, especially during the seasons. Also they tend to obtain permanent wear and distortion over the decades in cracked external wall coverings. A perfect example in your picture.
External lapped boards tend to hide this movement a lot longer than our later adaption to eml and plaster on the exterior of these timber framed cottages.

You can certainly hack off what is cracked and replaster as existing , but look at the frame movement in the area where the crack is shown in your picture.

Old Timber framed buildings can be high maintenance especially if they have been modified incorrectly by modern " thinking".

Good luck

Middi

 

[middi]

The reality is that old timber frame cottages have not the ideal framework to sustain rigid (or soft, ie- lime render) complete exterior coverings, they would have been rendered externally between studs, or, been completely covered with lap boards ( usually painted black ). Some later cottages lath and lime plaster externally.
The reason why external render ( especially the rigid kind on eml) is not suitable is because these cootages are always on the move, especially during the seasons. Also they tend to obtain permanent wear and distortion over the decades in cracked external wall coverings. A perfect example in your picture.
External lapped boards tend to hide this movement a lot longer than our later adaption to eml and plaster on the exterior of these timber framed cottages.

You can certainly hack off what is cracked and replaster as existing , but look at the frame movement in the area where the crack is shown in your picture.

Old Timber framed buildings can be high maintenance especially if they have been modified incorrectly by modern " thinking".

Good luck

Middi

 

[MikeG]

I don't want to be too much of a doom-monger, but that looks very much like the cracking and bulging you see when a sole plate is rotting away, and the house settling as a result. This can often be very difficult to see internally, where the only good face of the sole plate will remain. I would be quite surprised if this was just a question of poorly fixed EML and ordinary expansion & contraction, and I'd definitely hack the render off in that area to see what is going on inside the wall, as you're going to have to re-render anyway.

 

[steveb]

yes, indeed. beware of "structural render" that is actually holding the house up, when the timber inside has rotted away and no longer reaches the floor

(spoken from experience)

 

[DavidB]

Thanks for those replies many useful points. Re MikeG doom mongering a rolled sole plate could well be the problem!

The sole plate on that wall is well exposed internally and it actually looks the best 'original' piece in the house. There's a door right next to the crack and there are some finer vertical cracks adjacent to the door frame plus the window. So that stretch of wall is under more stress i guess and it is South facing and gets a big healthy whack of morning sunshine that heats it up quickly. But it's a good point and the sole plate i can see maybe a more modern repair.

My long-term plan was to hack it all off and put oak lath and lime plaster and i do already have listed consent obtained - but it is expensive, and i was thinking of perhaps just patching to avoid the upheaval.

Re Penner's question about the window _ i made the mistake of not measuring that gap when i moved in! I can't categorically tell if the gap has widened slightly. Re fixings - i cant see any nail heads or screw heads in the window frame or evidence of attachment to the building timber frame. They could be there and have failed or they may be non-existent. It could be that the window frame was set into the render and attached using raw plugs to the render and then patching render applied to cover the fixings and any gaps. If that is the case then that would explain the movement in the window frame. I.e. the render as moved and the frame moved with it. It's not how i would have attached the window frame though given the large building timber frame studs. You would have thought they would have attached the window frame to the building frame?

Maybe i will wait to i decorate that room and take the opportunity to strip off the internal plasterboard and see what's going on in there before attacking the wall externally. I guess it will wait another few months.