Lime rendering my timber framed cottage

[MikeG]

I know there is always quite some discussion about lime rendering here, so I though a photo-rich blow-by-blow account of rendering my house might be of interest. The basic summary of the walls of the house is that the front part is the old bit (300-310 years old, oak framed, insulated both between and outside the frame members, then wrapped in a breathable membrane), whereas the rear part is new, timber framed* with a vapour-permeable sheathing board.

*There's more to it than that


Anyway, here is the sequence, and it starts with the porch:

The whole point of building the porch now was so that I could get the render carrier board on and the render done before winter arrives. Once I sorted the membrane out, I did the boards up the roof junction with the wall, some window surrounds, and then some battens above:

The whole point of building the porch was so that I could prepare the house for rendering. To that end, I ran 3 rows of tiles (and associated lead soakers) each side of the roof alongside the house, and then mortared in the first of the ridge tiles. As I will be sitting scaffold boards on the roof for the rendering (called plastering everywhere but the UK, I think) I didn't want to tile the whole roof:

You'll note in those photos that I also put a vertical batten at each stud location, and fixed 4x1s either side of the windows, 3x1s above, and generally 2x1s below. I am now ready to tackle the window surrounds.

Because I am using render carrier boards, which are 15mm thick, rather than laths or "wire" (EML = expanded metal lath), which are much thinner, I need a little more thickness in the architraves around the windows than I was planning. To this end, I set up my planer in such a way as to be able to run long rebates in ex 75x19 PAR, then glued it to the architrave:

That gained me about 9mm in thickness, which should be about spot on. After fitting all the cills, I tackled the windows under the eaves first. Before, then after:

These three windows are done differently from all the others on the house, because they are tight up under the eaves. I ran the architrave around 3 sides. All the other windows will have a pentice board, which is a traditional local feature, simply a sloping board above the window head which keeps the top of the window dry. Here is an example:

I have always made these such that they can be removed and replaced even once the building is rendered. The fixings are on show underneath, so you would simply undo the screws and slide the board out. This is because the pentice board is highly vulnerable, and will be the first part of the exterior of the house to rot. So in 20 or 30 years time, or whenever, the can be replaced easily.

Here is the same window with its architraves in position:

And this is how the render carrier board will butt up to the sides of the window architrave:

The theory is that the render will be about 12mm thick. I reckon there is about 18 or 20mm of exposed architrave, which gives us a nice edge to finish against.

The Savolit Plus render carrier boards were delivered ahead of schedule this morning, so I got on and fitted a few. There were some bits and pieces to finish off first, and another coat of paint to do on the pentice boards and architraves. For access to the southern gable, here is my mobile scaffold:

I have to park it so close to the house that I shuffle across and climb out of the passenger seat. For any further work, I'll put another board or two up on the roofrack. Anyway, as a reminder, here is a "before" photo:

Then progress today:

This close up shows the load-spreading washers (stainless steel screws for lime, which eats anything else). It also shows that the insulation bulges the breather paper in some places so much that it touches the back of the Savolit boards:

The fix isn't difficult. Just push some battens in behind the boards:

Bingo, we have a proper gap, and airflow. The technical info from the manufacturer says that with the right number of fixings per board, and with full edge gluing (which I'll be doing .......I've left the appropriate gaps), that the ends of the boards don't need to meet on a batten. I ignored that, and made sure that all joins were fully supported. I was pleasantly surprised by how firm this substrate is. It easily took the weight of a ladder leaning against it, and that is prior to gluing.

The plasterer can't come next week, but so long as the weather stays something like he should be able to come the week after, and finally, after so long, the house will start to look a little finished.

 

[MikeG]

It's mainly been just more of the same for the last couple of days. Window surrounds, scaffolding, and Savolit boards:

I can't get any higher up the gables than that with just a tower scaffold. I'm getting hold of some scaffolding in the next couple of days. The corners are unusual in that there isn't going to be a stop bead and a square corner, but a rounded corner. The plasterer hates it, because he's got nowhere to stop, but it looks great when it's done. Here's the board detail:

I got sick and tired of the perspex over the porch, so cut up some spare glass I had and pinned it into the window openings:

It's just temporary, to get us through the winter without getting the inside of the porch wet.

For fun, let's start at the end (latest) and work backwards. I've just been plodding on with the render carrier boarding:

I don't even have planning permission for a conservatory, nor any sort of drawing, but we want one, and so I had to make allowances for it. I fixed a whole lot of 6x1 to the house so that I've got something firm to make the connections to if and when it happens:

Then window surrounds and battens:

As a record of where the conservatory 6x1s are, I took these:

That half gable in the second picture took an awful lot of work, because there is a lead flashing and a drip bead detail, and with rounded corners and small clearance under the window I spent an hour or three lying down on my home-made scaffold platform. You can see now why I haven't slated that roof yet!

The plasterer dropped by to check on progress, and told me he can't come until next Monday. So I have a comfortable week to be fully ready for him, with scaffolding up.

This is all about getting ready for rendering: getting Savolit boards up everywhere, getting scaffolding up, and getting guttering done. The guttering is important because lime render doesn't set as quickly as sand and cement, and would be vulnerable to rain for a few days after going up (in the case of putty lime, make that a few weeks). So, let's start with the guttering.

Because I have no fascias, the gutters have to fix to the side of the rafter feet, or in my case sprockets. Naturally, the brackets were all too long, so I had to cut them to length. I put the end two brackets in place (one at each end of the roof) and string a line between them so that the guttering doesn't wave in and out or up and down. We'll come to falls in a minute:

On the rear of the house, the new part, all went well. The roof is 10 metres long, and I laid it to fall 50mm in that distance. No problem. On the front of the house, the old part, it wasn't so straight forward. I wanted all of the water to end up at the north end of the roof, and set up a bracket at either end as before, then strung a line. I put the line 60mm lower down the bracket at the north end, but happened to notice that it lined through perfectly with the window head. I grabbed a spirit level and checked, and lo and behold, the string was absolutely level. In other words, the roof sloped 60mm the wrong way. To achieve the falls I wanted the gutter would have to fall 120mm from the eaves line, which would mean it would foul the windows, preventing them open. My 3 year old plan of taking all the water from this roof into the pond had come to nothing.

All I could do was put the outlet half way along the roof, and then I'll take the downpipe into the porch gutter. There is no other drain connection I can get onto:

As an aside, the long "tail" to the gutter brackets fouled the 3 front windows, unless it was fixed to a rafter foot directly above the middle of the window. In a lovely little piece of fortune, for no reason at all each window had a rafter bang in the middle! Sometimes luck is on your side.

So, that's the guttering up. Next, I needed to put up a proper gable scaffold. I had most of the stuff, but had to go and buy a bit more. In the yard I was stunned when the guy helping me picked up three 13 foot (4m) scaffold boards at once and popped them nonchalantly on the roof of my van! Three!! I didn't even try and compete, and just did one at a time. Anyway, the scaffold:

I finished all the Savolit boarding except for part of the back wall:

I'll take a close up of the leadwork over the future conservatory roof next time.

So, finally I was ready!! I had half a ton of lime render in the van:

Mr Reliable turned up exactly when he said he would, and apart from a funeral tomorrow will stay with me until the job is done. We experimented a little with the mixing of the render:

This shows all the fibre in the mix:

There is no sand in it at all. This is exactly what I found with the plaster I took off both inside and out on the old part of the house. No sand, but lime, horsehair and chalk. The modern equivalent is lime, poly-something fibre, chalk, and bobbly insulating something or other. It will dry just as flexible and vapour permeable as the original.

I could have lost a lot of money betting where the first float-full of render would go. I'd have said bottom right hand corner of the wall, as the plasterer is left handed. No, it was right at the very apex of the gable:

It went fantastically well! The boards were a perfect background for rendering, meaning a relatively thin single coat was all that was necessary, saving time and lots of money. You stop putting the stuff on the walls about 2pm, because you are then spending the rest of the day trowelling up, and working the surface as it dries, before finally, I went around with a damp sponge just rubbing up the surface a little. It brings the grains to the surface, leaving a slightly roughened rather than smooth texture. When I finish typing this I'll be going out to do the stuff that was put on later, which is still too wet. Plastering isn't hugely skillful, but is all about timing. Anyway, I couldn't be more thrilled with the result (remember, this will be limewashed in the spring, so the bright colour will disappear).

Because of the rounded corners, there is no natural stopping point on the main elevation of the house. I screwed a temporary batten in place to stop against, and the plasterer embedded some scrim in the plaster as he came up to it:

I "dubbed out" the bottom of the walls where there is a splay, using a drier mix. Nonetheless, because of the thickness, the render at this location, and the corners, is still very wet and I'm likely to be sponging them up using a head-torch at bed-time this evening!

I took as much of the scaffold down as I could, to move it to the other end of the house tomorrow:

Now, I've got to go out and sponge away the last of the toolmarks.........

 

[MikeG]

I had to take the scaffold down from the gable, and the final part of that process always involves leaning the last 2 poles and first-lift cross-member back against the building. I didn't want to damage the new render, so I strapped a couple of big pieces of foam (old chair cushions) to the top first :

I also cleaned up the brickwork from Monday's rendering:

Then I chased around all day labouring for the plasterer, and we got an awful lot done. The first photo still has the scaffold in place:

As I write, at 7.30 and pitch black outside, it looks as though the bottom corner will be ready to "trowel up" in a couple of hours, by torchlight, as it is still very wet. It isn't impossible that I'll be working on it first thing tomorrow morning.

Oh, and here is a close-up of the render meeting the porch roof, scratched ready to take a 45 degree fillet of tile and mortar:

Finished!!

The whole building is done in only 4 days, some 4 days less than I'd allowed for, using 61 bags of lime (19 less than estimated). My hands are ruined, but other than that, I am delighted. So delighted that I'm going to have a few days off. Anyway............photos:

The grey line below the windows in the last photo is lead flashing, built in now in the hope that we get permission in due course for a conservatory. It's going to look pretty silly if we don't!

Attention turns temporarily to the porch roof. Here is the junction between the roof and the render, prior to starting work:

I cut some tiles in thirds, lengthways, and mixed up some of the lime render stuff, then did this:

This is a really old traditional detail, done to keep water out of the junction, but you may remember from some while back that I had also done lead soakers up this roof/ wall joint, so this is something of a belt-and-braces approach. I don't think the modern lead cover-flashing with render drip bead looks any good on a period property, so I've done it this way instead. It has the bonus of kicking the dropping water a few inches away from the wall, so it will all go into the gutter without the need for a bodged in bit of lead.

(Edit: no.......it still needed a bit of bodged-in lead!!!)

 

[88v8]

We'll come to falls in a minute:

On the rear of the house, the new part, all went well. On the front of the house, the old part, it wasn't so straight forward. I wanted all of the water to end up at the north end of the roof, and set up a bracket at either end as before, then strung a line. I put the line 60mm lower down the bracket at the north end, but happened to notice that it lined through perfectly with the window head. I grabbed a spirit level and checked, and lo and behold, the string was absolutely level. In other words, the roof sloped 60mm the wrong way. To achieve the falls I wanted the gutter would have to fall 120mm from the eaves line, which would mean it would foul the windows, preventing them open. My 3 year old plan of taking all the water from this roof into the pond had come to nothing.

All I could do was put the outlet half way along the roof, and then I'll take the downpipe into the porch gutter. There is no other drain connection I can get onto:

Another wonderful post.
Thankyou.

Just a thought:

Take the water to the 'wrong' end of the roof, run a downpipe to just below the window cills, then take another gutter across the front, back to the 'right' end. The outlet into the lower gutter would have to be angled in the desired direction of flow, otherwise it will overflow.

I'm eyeing this from the photos, a lower gutter might just skim below the ciil and above the apex of the porch?

A quirky solution, but it would get the water where you hoped, you know where the studs are for making the fixings, and future generations could enjoy sailing little yachts from one window to the other.

Ivor

 

[MikeG]

That would be...........erm............quirky, Ivor!

 

[Flyfisher]

Thanks for another interesting and informative post, not to mention another job very well done.

I've previously mentioned that I very much like rounded corners when plastering inside walls but yours is the first time I can recall seeing it done externally - it looks gorgeous!

 

[MikeG]

Thanks.

I've found this detail is one of those that clients and others don't understand until they see it in the flesh, so to speak. People will stare at a newly-rendered building and say it looks beautiful, but not know why. When you point them at the rounded corners, and the lack of other beads, the penny begins to drop.

 

[Zebra]

That's fantastic and extremely informative, MikeG. I love the rounded corners too, and wish I'd done this on mine. What did you use to glue the boards together, please? (I used these boards internally, and used gripfill successfully, but have no idea whether this is right!)

 

[MikeG]

Thanks.

The glue is a PU foam supplied by the board's suppliers. It doesn't expand like the usual foam, and seems to set harder. Reading the tin it seems to be the stuff which is supplied these days for sticking plasterboard to blockwork. If you leave all the joints open 5mm (I used off cuts of ply as spacers), and you do all the gluing up in big batches, then you'll only need 3 tins maximum for 100 sq metres, less than half what the supplier recommended to me. I really cant see why Gripfill wouldn't work nearly as well, although the foam was great for securing board edges in awkward corners and around windows. It's purpose is to stiffen up the substrate, rather than to prevent joints showing through the render as cracks.