Silly brickwork question.......

[JDLDIY]

I have a number of repairs to do to the exterior facing brickwork of my house. Most of them will involve replacing damaged bricks with new ones, or filling holes with new brickwork such as now. We have replaced the boiler, leaving a big hole in the wall. My question is, when installing bricks vertically, without completing a whole course during which time the mortar would presumably set a bit, should I mix the mortar differently from the start or wait a length of time before placing brick on brick?
I know this maybe a silly question, but I've not attempted brickwork before so ANY tips greatly received.
JD

 

[TexMex]

I'm not quite sure I know what you're asking. Are you concerned that, building the wall too high, too quickly, will result in the mortar on the bottom course being squished out?. If so, don't worry, it wont.

As for general tips:
Your mortar mix will depend what you have already. If you have a cement based mortar, don't forget to add plasticiser to the water before mixing. It really does make the job much easier and reduces the likelyhood of the mortar shrinking away from the bricks, as it sets.

You want the mixture to be fairly wet, but not runny. You should be able to mound it up into a heap, but be able to put a sheen on it, with a single wipe, of the back of your trowel.

Before you start laying the bricks, wet the existing wall, around the area to be filled, and allow to stand a few minutes. This will prevent the existing brickwork sucking the water out of your mortar too quickly (which leads to a poor bond between the new and old brickwork).

As you lay the bricks, use a CUTTING motion with your trowel to remove the excess mortar, that is squeezed out of the joints. DONT attempt to rub it off. This is probably the most pervasive mistake made by amatuers and makes a right mess of the brickwork.

Finisihing off the joints is another whole subject in itself. If your existing brickwork has been pointed as a separate job, you may find that the mix used for this is much stronger (say 1:3). If this is the case, rake out your joints to a depth of about an inch and brush the wall face off with a stiff broom, ready for repointing with the stronger mix.

Whatever you do to finish your joints, Don't forget to brush the front face of the wall, once you have finished. Use horizontal strokes with a broom. Do this at least 20 minutes after you have finished the jointing, but not much later. You'll definately see the difference. It takes all the ragged edges off the joints, and removes the small dots that have fallen onto the brickwork.

Good Luck.

BTW. If you are filling in a large area, you should also consider wall ties and insulation.

 

[JDLDIY]

Thanks for the advice TexMex. OK, this being the first time I have undertaken any masonry, I am still in the research phase! I have taken a few books out of the library to read, but I still have a few questions to ask.
On the grounds that a picture is better than a thousand words:

This is the hole where the boiler was. Interior leaf was filled by builders with blockwork, exterior leaf needs filling.

This is an internal hole to be filled, near to some recent building work.

1 Tools. I have just bought an 11inch broad heel brick trowel. It doesn't appear to be thicker on one side than the other (which I just read about) and it doesn't have one side straight and the other not. I just read that London pattern trowels are better suited to cavity wall work. Any recommendations here?

2 The existing, original mortar is a really grey colour, how can I best replicate that?

3 I want to repair the holes using whole bricks (I have some spare from building work already done). So, I anticipate cutting out the originals using a plugging chisel. Then building up in courses of new bricks until I reach the top of the hole. The last course then remains (whether just 1 brick or more). The thing is that presumably the strength of mortar joints rely on the fact that as the bricks are laid the mortar is compacted and ensures good adhesion to the bricks, leaving no spaces in the joints. How can I ensure that when inserting the last buttered brick and presumably not applying downward pressure?

4 More of a structural question really; how big as a guideline can a hole be before I need to worry about support work? The boiler hole will be 3 bricks wide at it's widest and 5 courses deep. Gut instinct tells me that won't be a problem, just checking.

I tell you what there is a business opportunity here. I've been looking out for some video instruction in bricklaying. As far as I can tell the most important thing to get to grips with is the whole physical technique of using the trowel, laying the bricks etc and I can find nothing. The right tuition in video format would be really useful, but the only video I found was absolute rubbish. Similarly the only good book I could find on the subject, designed fro DIYers, is written by an American and from what the inside cover says I don't think he's ever built a brick house, just loads of chimneys and fireplaces!

 

[TexMex]

As far as trowells are concerned, I'd usually recommend, whatever you're used to. My normal choice is a Northern pattern, (Like a London, just a bit broader), but I sometimes use a Candian pattern for thicker walls and on really thick walls, I get the labourer to dump the mortar on with a shovel, then I spread it with the trowell. Since you're not used to anything in particular, what you've got is probably as good as any.

That mortar does look a bit strong. Examine the mortar in the edge of the exposed broken brickwork. Does it look the same colour right through the thickness of the outer skin. If so, I'd go for a 1:4 mix (cement to Building Sand). If the main body of the wall is lighter in colour, I'd go for a 1:6 mix to lay the bricks, rake out the joints, then point up with a 1:3 mix.

Since you have the obstacle of the soil pipe, I'd be inclined to break the bond and go for quater bond instead. To do this you would remove the bottom two bricks, the top two bricks, the half bricks on each side of the opening, and then, with an angle grinder, cut the other four bricks back to 3/4 length (looks like the silicone is marking where to cut).

Your new brickwork would then be alternating courses of 2 full bricks followed by 3 half bats. (See my crude emulation below). When cutting the 3/4 length bricks, note that the gap you need for three half bats and their joints will be about 350mm.

When cutting the half bats, just cut the bricks across the middle, then lay with the cut edge into the wall (ie. the original end of the brick will be exposed on the face of the wall). Make sure that you have a clear gap between the outer and inner skin. If the half bats come out too close for comfort, chop a bit more off them. Don't worry if they aren't quite the full thickness of the outer skin, you can easily get away with them being 30mm too short, without any worries.

Once you lay the bricks, don't attempt to cut off the mortar that squidges out on the cavity side. Like as not, you'll drop it down the cavity (where it can pile up and cause a breach just above the DPC). I know it looks like a runny nose just waiting for a tissue, but if you Just leave it hanging, it will do no harm.

When laying the joint for the top course, don't overdo it. When laying the a brick for the top course, fill the frog and put another joint on top of it. Make this joint just about 20mm tall and only along the cavity side edge. As you push it into place, it will naturally get spread out across the top of the brick. Put your trowell against the top of the brick to catch the excess that gets pushed off of it (This will probably be most of it ). To press it down into position you may find it handy to poke a cold chissel through the top joint to act as a lever. Just accept that you will have to fill the top joint by forcing the mortar in afterwards.

I've just noticed that the mortar on the inner skin looks the same as the outside. Chances are it's about a 1:4 mix. Don't forget the plasticiser. The fairy liquid bodge is no good unless you are using a mixer (I take it you're not).

The jointing is run of the mill rubbed joints. Find any plastic or metal item with about the right cross section to rub them with. I find the oval cross section of those stanley screwdrivers good for small areas. For thin joints you use it with the narrow edge into the joint, For thicker joints you use the broader side. In between sized joints, use it a somewher inbetween. (No good for large areas as they quickly become rather scratched). By rubbing narrow joints deeper, it disguises the difference in joint thicknesses.

If you take more than, say, an hour to lay the bricks, rub the joints that you've done so far (vertical joints followed by horizontals). About 20 minutes after the rubbing, brush with a broom, (using horizontal strokes).

Just one minor point on the inner skin, instead of rubbing the joints, leave them raked out (about half an inch should do). This will act as a key for your render/plaster.

Structural supports? No I don't think so. You could, of course, save all this trouble by just fitting a cat flap.

 

[JDLDIY]

Since you have the obstacle of the soil pipe, I'd be inclined to break the bond and go for quater bond instead. To do this you would remove the bottom two bricks, the top two bricks, the half bricks on each side of the opening, and then, with an angle grinder, cut the other four bricks back to 3/4 length (looks like the silicone is marking where to cut).

I'll certainly consider that TexMex, but I'm fairly keen to use full bricks so that it doesn't look as if the wall has been patched up. The soil pipe actually stands far enough away from the wall to gain access to do the work, but that doesn't show up in these pics.

That mortar does look a bit strong. Examine the mortar in the edge of the exposed broken brickwork. Does it look the same colour right through the thickness of the outer skin. If so, I'd go for a 1:4 mix (cement to Building Sand). If the main body of the wall is lighter in colour, I'd go for a 1:6 mix to lay the bricks, rake out the joints, then point up with a 1:3 mix.

Lost you a bit here I'm afraid. Yes the mortar looks the same colour all the way through, I don't think that the brickwork has ever been repointed or worked on at all. Do I take it that the more cement used, the lighter the mortar colour, or the other way around? What would be the advantage to using 1:6 mix but then pointing in 1:3 as opposed to just using 1:3 for the whole job?

Next question - wall ties. If I inspect the areas concerned and find that I really need to fix one or two wall ties, how is that done bearing in mind that 1 leaf of the wall is already in place and which type of wall tie do I go for?

Cheers again

JD

 

[TexMex]

but I'm fairly keen to use full bricks so that it doesn't look as if the wall has been patched up. The soil pipe actually stands far enough away from the wall to gain access to do the work, but that doesn't show up in these pics.

Go for it, by all means, but it is not just the preparation that will be harder. You may find putting the bricks into half brick toothings (and getting them level) trickier than you imagine.

Lost you a bit here I'm afraid. Yes the mortar looks the same colour all the way through, I don't think that the brickwork has ever been repointed or worked on at all. Do I take it that the more cement used, the lighter the mortar colour, or the other way around? What would be the advantage to using 1:6 mix but then pointing in 1:3 as opposed to just using 1:3 for the whole job?

Mortar (for bricklaying), should be consistent with the type of brick being laid. A mix as strong as 1:3 (above the DPC), would only be used for engineering type bricks. It's use with softer brick types would be contra-indicated (as they say on ER ). Using this mix with sand faced commons could lead to errosion of the bricks, in due course.

A 1:3 mix for pointing, however, is routinely used. Irrespective of the type of brick.

Bearing these points in mind, my reasoning was as follows:

The joints in the picture look like a strong mix (stronger than say 1:5). If, the joints that I can see in the picture are the actual mortar used to lay the bricks, it is unlikely to be stronger than 1:4 mix. In this case you may as well use the same.

If, however, what I am seeing is mortar used to repoint the wall, I am probably looking at a 1:3 mix. To reproduce the same on your wall, you would want to point it up, with a 1:3 mix. In this scenario, I have no way of knowing what bricklaying mortar has been used, but since the joints are going to be protected by the pointing, the exact mix would not be too important. I simply chose 1:6 for it's better performance in terms of water diffusion. All academic now anyhow.

Wall ties are usually placed at 900mm (4 brick lengths) intervals horizontally, every 6th course. So the maximum number that you would want in your small area would be one. If you really want to put one in, you could use a timber frame tie. These come in many designs but here's one example. You'd just use a screw (zinc plated) and rawplug to attach it to the blockwork.

 

[JDLDIY]

Mortar (for bricklaying), should be consistent with the type of brick being laid. A mix as strong as 1:3 (above the DPC), would only be used for engineering type bricks. It's use with softer brick types would be contra-indicated (as they say on ER ). Using this mix with sand faced commons could lead to errosion of the bricks, in due course.

Wow, I never knew that! What would you refer to the face bricks shown in the photos above as - are they "sand faced commons"? What actually causes the errosion of the bricks?

Another silly question - does the increased percentage of cement mean that the mortar sets harder in the long run or makes little difference?

JD

 

[JerryD]

It's impossible to tell the strength of the mortar mix on your house without analysis. The colour is not a reliable measure. Our local builders merchant sell two types of building sand, one is pale and the other is orangey. Mix two batches using the same amount of cement and the pale sand mortar looks ten times stronger than the orange sand mortar.

I'll bet the mortar used on your house was standard 6:1 sand/cement/plasticiser.

If you use very strong mortar the brick may erode over time as the mortar becomes harder than the bricks. Freeze/thaw attack and general weathering will attack the weakest part of the wall, which in this case would be the bricks (strong mortar + weak bricks). It is much cheaper to repoint a wall after 50 years than to re-brick it!


.....and yes, a stronger mix will become harder

 

[JDLDIY]

I just bought some WINTAMIX by FEB, the instructions don't really help too much with the proportions, they say 5L per 100Kg cement. I'm only doing small jobs, how much should I add as a proportion to the water added?

 

[TexMex]

5L per 100Kg cement. I'm only doing small jobs, how much should I add as a proportion to the water added?

About a half pint per gallon should be about right. In extreme cold (Lower than 4 below Zero Centigrade) you should increase the dosage, to a pint per gallon. You should also increase the dose if your sand is excessively wet. (as you won't be adding so much water).

 

[mildmanneredjanitor]

(See my crude emulation below).

As in Top Secret/Back to the future???

 

[TexMex]

As in Top Secret/Back to the future???

Sorry MMJ, lost me there but I did a search on www.google.com for "crude emulation below" to see if any referrances to Top Secret or Back to the Future came up, and guess what?

This post came out top of the list Imagine that! With all the websites, in all the world, one of my quotes comes out top of the list

 

[mildmanneredjanitor]

Sorry MMJ, lost me there but I did a search on www.google.com for "crude emulation below" to see if any referrances to Top Secret or Back to the Future came up, and guess what?

This post came out top of the list Imagine that! With all the websites, in all the world, one of my quotes comes out top of the list

Don't let it go to your head!

In Back To The Future, when Doc Brown is describing to Marty the plan how to return to the future in the Delorean, he uses an intricate model of the town of Hill Valley and says 'Please excuse the crudity of the model'

And in the Film Top Secret, as Nigel (The resistance leader) starts scratching an attack plan in the earth with a stick, as he proceeds, models of the chateau, animals and railway pan into the picture!

Just very funny moments... To me anyhoo!

 

[TexMex]

In Back To The Future, when Doc Brown is describing to Marty the plan how to return to the future in the Delorean, he uses an intricate model of the town of Hill Valley and says 'Please excuse the crudity of the model'

Ah, yes, I remember it well. The model car flying off the table in flames was even better though.

I don't think I've seen the film "Top Secret". Sounds like it could be my sort of thing though. I'll have to see if it's available on video.

 

[mildmanneredjanitor]

Linky

From the makers of airplane etc. But this is their finest work!

'What's the damn hurry! Why are we always in such a rush!'