Huge gap between window frame and brickwork - please help.

[vickymess]

After removing the paint from our Victorian terrace, we are left with huge gaps between the sash window box frame and the windows. I have no clue what to do, and am worried the house will fill with water and collapse. Do I get expandable foam put in (this seems counter intuitive as I've had the paint removed and had lime pointing to help the house breathe)? This is the suggestion from the fella who removed the paint (he suggests then putting trowel or tub mastic over it to seal). But the gaps are large (up to 5cm in places) and the space seems to go deep (there also seems to be a bit of rubble in there?). Any advice what to do? (Ps. I am not very DIY handy).

 

[stuart45]

Can you get some photos on?

 

[vickymess]

Can you get some photos on?

I think I have put the photos on correctly now.
Hello, I've just put some photos on. Thank you.

 

[Cubist]

Hi Vicky and Welcome,

Your photos have not appeared on the site, could you try again please?

You are right to be concerned about water ingress, all the gaps around the window frame must be made weathertight as soon as possible - the next few days may be the perfect opportunity.

Trowel mastic is commonly used for this purpose as it will, if properly applied, make a good weathertight seal to both the brick-work and the window frame. It also retains its flexibility to cope with expansion and contraction movement of the frame in particular and also the brickwork and mortar. Usually it is used with quite wide gaps, upto say 10mm as this allows the operator to press the mastic firmly into place to a depth of around 25-30mm, or more if desired. This forms a wedge of the material that operates, in addition to its adhesive qualities, to create mechanical grip on the surrounding materials. If you're thinking of doing the job yourself be generous. Once the gap is packed with the mastic it can then be 'polished/smoothed back' with the side of a slightly oiled trowel.

Commonly trowel mastics are brown in colour and, as it dries, it takes on shades that may be a good match to the brickwork. If you are thinking of painting the finished mastic joint you will have to wait a few days for the surface to firm up enough to do so effectively.

The very large gaps may need additional work before the mastic is applied. Its not unusual to find that the builders/earlier repairers mortared an off-cut of matching brick into place and held this in place temporarily with wooden wedges while the mortar sets before applying the mastic.

Don't be concerned by the overall depth of the gaps. Its normal for these to extend to almost the full depth of the window casement.

If you can get the photos loaded the other contributors or I would be happy to provide any additional advice and alternative approaches.

Cheers,
Cubist

 

[vickymess]

Thanks so much for your reply, Cubist. Hopefully the pictures have posted properly now.

 

[Cubist]

Hello again Vicky,

Thanks for the photos; very enlightening but also very puzzling.

Normally, window and door frames are installed from outside the property and their outer face is set roughly 50mm below the exterior face of the brickwork. This window frame is, for some extraordinary reason, seated on the inner brickwork that forms the interior wall but has not been positioned to meet or even remotely close the gap to the inner face of the exterior brickwork. I cannot think of a valid reason why a builder would do this so I'm thinking that the entire window frame has been replaced at some time in the past. Either the replacement frame was too large for the opening in the exterior brickwork and could not be installed from outside or the installer set the location on the basis of the inner wall rather than the external as he should. Are there similar properties nearby that have similarly position windows? If there are they could provide some clues to confirm/deny that hypothesis.

The right thing to do, I think, would be to re-position or perhaps replace the windowframe but that would likely be a very expensive and certainly difficult and time consuming task. With autumn approaching it is vital this issue is addressed soon and with this on mind I would suggest: -

1. The gap between the outer brickwork and the window frame is too large to allow the use of trowel mastic alone.
2. The gap was probably previously filled with a fillet of perished mortar which in all likelihood had been held in place by the paint.
3. A stainless steel wire mesh - the chicken wire available from garden centres - can be rolled, crushed and shaped so that it can be pressed into the gap to act as an armature/skeleton.
4. Mortar or trowel mastic can then be pressed into the mesh to fill the gap and bring the surface face to the desired height.
5. If mortar is used rather than trowel mastic; once the mortar has set a bead of mastic should be run around the seams between the brickwork, mortar and window frame.
6. And of course, paint when dry.

Sorry but this is the best I can come up with. Maybe some of the other members here will have a better idea for you but please reach out if you need any clarification with the above.

Cheers,
Cubist

 

[Stevers]

We had this problem in our previous house in Yeovil. It was an early example of cavity wall construction (1913 and first in a street of similar houses) using the unholy combination of black japanned wall ties and an ash mortar. The result was that on the exposed west elevation, the ties had corroded away, and the outer skin had moved away from the inner skin. Once galvanised wall ties had been fitted to stabilise the wall (the traditional way four bricks at a time), I cut some wooden trim pieces that I fastened to the sash box to close the gap to manageable proportions that could readily be filled with mastic. The extra trim pieces, that needed to be tapered in my case, were treated with preservative and everything primed all round before fitting.

 

[stuart45]

Looks like recessed jambs, which were sometimes used to protect the frame, and inner reveal from driving rain. I think it's a reg in Scotland.

 

[stuart45]

Cubist's idea of mesh seems as good of any simple method. On site a combination of old cement bags and yesterday's Sun would be used.
Probably the neatest method if you could find some matching bricks would be to cut out the half bats. Fix some 6inch DPC up the frame and return the brickwork against the DPC using 3/4 bats and 1/4 closers. Or just use closers.
Another way is to use DPC as before, but mortar up pieces of slate and stick them against the brickwork . Probably need 2 or 3 courses half bonded.

 

[Cubist]

Not sure I'm the author of that idea. I seem to recall that it was either Clifford or Ivor that added the stainless steel spin in preference to the galvanised wire I had used until then.

As an aside; finding the odd scrunched up cement or plaster bag in some otherwise vacant cavity was always a source of annoyance and not least because the local mouse population had been at it for nesting materials. Never found a copy of the Sun though, maybe the builders I indirectly encountered were more discerning but that may be stretching credulity a little far.

 

[stuart45]

I used to work with a chippie who read the Guardian at tea break. Looked quite funny when he seated next to one of the labourers reading the Beano.

 

[malcolm]

The window being wider than the face brickwork is normal for sash windows. The windows were fitted from the inside where the brick opening was half a brick wider than the outside facing in order to hide the sash boxes.

Originally the gap between the window and outer face would have been 5mm to 10mm. The gap in the photo is far too large. I'm going to guess someone has refitted the window badly, probably when they rebuilt the arch above. The ideal solution would be figure out how they secured the window, remove it, clean up the opening and make it how it should be, then fit the window properly.

Failing that just fill up the gap. It's an awkward gap - too big to just shove lime mortar in. I think I would fill it with lime mortar then shove a piece of slate down the middle. Leave it 20mm shy of the surface and finish it with lime mortar.

Avoid anything waterproof against wood like DPC membrane or modern paints. Wood is permeable and sometimes absorbs water and sometimes lets it out. When it tries to let water out to a waterproof membrane the water gets trapped and rots the wood.

 

[stuart45]

One of the main problems with windows sitting in a recessed jambs or check reveal is that it is often up against damp brickwork for long periods.
You often find some rot the timber here. A DPC does protect the timber against this, so it's seen a a better solution. On modern check reveal, the DPC goes inbetween the frame and brickwork.
If it's a cavity wall, and the inner skin is returned, the DPC should go between the skins and behind the frame.

 

[malcolm]

Modern houses will have the outer bricks built with cement so the bricks will be soaking wet. It's no problem as the bricks are modern and designed to be wet and modern houses won't last long. I can see a DPC helping to protect the wood. In an older house built in lime the walls should be dry and a DPC would be a bad idea as it would stop water ending up in the wrong place from drying to the lime.

 

[stuart45]

Later houses built in lime still had vertical DPC's. Having worked on quite a few older houses with this kind of brickwork, I've seen rot in the frames caused by this. The DPC put in when the frames were repaired and put back in wasn't seen as an issue. A box frame should be able to breathe OK, even if there is a DPC on one side. Just because a wall is built in lime doesn't guarantee it will be dry. If there's been a issue with the frame getting damp it was a standard thing for the chippies to use a vertical DPC in front of the frame.
Taken from a 1902 textbook.

 

[vickymess]

Wow. Thank you everyone for your replies, this is really useful and interesting information. I wonder if someone could tell me what a DPC is . Also, what are 'bats' and 'closers'?

 

[Cubist]

Hi Vicky,
DPC - Damp Proof Course; usually a layer of of water impermeable material laid horizontally between two courses of bricks near ground level to inhibit/prevent rising damp from the ground. These are sometimes installed vertically between cavity walls to prevent penetration of driven rain.
A 'bat' is a brick that is cut to a needed depth, say half or even a quarter, that is then used to complete or close a gap of an irregular depth - or width if installed vertically - during construction of a wall.and are often found near window and door opening in the brickwork. These are also sometimes referred to as a 'closer' but specially cut or pre-shaped bricks are also used for this purpose.

Welcome to the 'brickies' tech speak lingua franca. Don't worry, you'll get used to it - it can take a long time, but we have lots of nerds here who will help.

Cheers,
Cubist

 

[stuart45]

Well explained by Cubist.
Vicky, if you look at the diagram for the square reveal it shows 3 slates for a DPC, which is a possibility for you. Easiest method is to butter up a slate and push it against one side of the opening. Do the same on the other.
Then butter up both sides in the opening. Cut a slate in half and butter up both sides and place inbetween the other 2, Carry on like this up the jamb, using full slates in the centre now.
Worth fixing a few cut nails across the cavity to make sure the slates don't slip down a bit, or a bit of slate across the cavity.
If you have a Victorian cavity, it must be one of the early ones. They didn't have any DPC's to begin with. Are you in Hampshire? Portsmouth had loads of them built from1860 on.
Saying all this, I still like the method mentioned by Cubist.