Repairing Cement Mouldings

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houseman
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Repairing Cement Mouldings

Postby houseman » Sun Jan 01, 2012 6:13 pm

The exterior of our house has several decorative mouldings: under the eaves and around the windows and doors. Some of these have been damaged by earthquake and frost: some of it is just flaking of the top coat, but some goes deeper, and there is one window sill where a chunk the size of two fists has come adrift from the brick base.

Has anyone had experience of repairing such things? Would they consider it a suitable job for a DIY-er with some basic tools and experience? What would be involved?

Or is it best left to a Master to do the usual half- a*sed job at a rip-off price? (no disrespect to the only decent tradesman in the village!)

The more practical the reply the better, please.
Last edited by houseman on Sun Jan 01, 2012 6:55 pm, edited 1 time in total.

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Ontario
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Postby Ontario » Sun Jan 01, 2012 6:46 pm

Do you have a complete one you can take a mould from to replace any that aren't repairable?

I'd class it as a DIY job but have experience of renovating houses, i.e all childhood working on various family homes (and they said slave labour was dead).

One point I would make is you need to check the material of originals and repair with same ideally. Also make sure MOST IMPORTANT you take back to solid base.

I'm sure that somewhere online there will be information on repairing moldings that you will be able to adapt to suit your requirements.

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houseman
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Postby houseman » Sun Jan 01, 2012 7:01 pm

Thanks Ontario, I wouldn't have a clue how to make a mould from an existing moulding, other than suspecting it would invoilve wood shuttering.

I have looked online and as usual what comes up is a whole host of not very useful stories about individual jobs, firms selling patching products etc., tales of woe about things going wrong......

Enough to put me off, but I am still curious about the process and materials.
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Postby seathrift » Sun Jan 01, 2012 9:07 pm

The only way I can think of suitable for DIY is to use a very fine grout with a resin based hardener. This may enable you to get a thin enough finish that it can be trowelled in and then sanded to match the original. This would allow for feather edges that will save you digging out chunks of the original that would be necessary if you were to use traditional silver sand and cement. I Assume that you will then be painting the completed works, because colour match of concrete needs a well practiced expert.
If you're not bothered about exact matches then using glass fibre and a resin hardener would have much the same effect, but you would need ambient temperatures above 12°C for it to go off properly.

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Postby Ontario » Sun Jan 01, 2012 9:19 pm

You could use liquid latex to obtain a molding, build the thickness up in thin layers.

As this is a Bulgarian property we are talking about I would not just assume it to be concrete - fine details can be incorporated into mud plaster.

From a personal satisfaction point of view you might consider repairing one that is 'less visable' to see how you get on.

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Postby houseman » Sun Jan 01, 2012 11:12 pm

Thanks for those two suggestions. I'm pretty sure from the look and feel of the debris that it is just cement and sand, unless there's lime in it too.

Seathrift, you're right about sandy stuff being awkward to blend in: I tried on another less important job, and it just "wants" to build another layer. Wiping it carefully off where it invaded the existing moulding was the answer.

It will all be painted. BTW if "latex" is the Bulgarian word for vinyl based paint, what is the word for latex (as in the mould making)? Is it even available?
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Postby Moscow_Wolf » Mon Jan 02, 2012 9:31 am

If you cannot find a suitable way of repairing the existing ones and if they're purely decorative and have no supporting purpose, you may try making some replacement new ones yourself from a suitable piece of polystyrene, coating them with some mesh and then adding something like CM 11 (the same way that Bulgarians add insulation to the outside of houses here). You could then seal them with a suitable outdoor finish or paint.

You might even consider using 12 x 12 cm block-wood shaped with a jigsaw under the eaves and/or sterling board for around the windows, but it would help if you could stick a photograph of the mouldings in your gallery so we could can see their form and shape.

How old 'roughly' is your house? Perhaps the Meister that did those original mouldings is still around.

Sounds like an interesting challenge all the same.

Good luck.

mrmike

mouldings

Postby mrmike » Mon Jan 02, 2012 10:18 am

you could try forming a box around a complete mold cover the existing mold in tin foil form a box around it and fill the box with expanding foam from a can leave for 24 hours then take off the boxing and then you have a mold to work with that you could fill with sand and cement making sure you treat the inside of the mold

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Postby houseman » Mon Jan 02, 2012 10:26 am

Thanks MW. The pics will have to wait till our spring visit, not having taken any to date.

If I only had a router and lots of scaffolding there's a lot I could do, but time is limited to about 3 weeks at a stretch, and that's without all the other stuff that needs doing and organising.

The house is from 1957, so the Master will be retired by now, if not deceased, and I'm not sure I can cope with all the probable blind alleys and diversions involved in asking locals who did the job - assuming I can use the correct phrases to ask.

You know how it is.... :lol:

Thanks also MrMike: that would be a good way of fabricating a complete new moulding and I will bear it in mind if the job goes that way. At the moment it's more of a patch and fill exercise apart from one chunk. :)


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