Quality of Extension Workmanship

[newuser1]

Could someone please offer some advice.

I am having an extension and some of the joists have been installed and I am wanting to know if they look o.k? The builder seems to have used about 2 inch thick mortar to level the joists and I need to know if this is good practice.

He has also used old bricks below them put thick mortar again to raise the level but shouldn't the joists be resting on brick/blocks? Using just mortar underneath the joists, can this cause any issues with stability of joists/floor over time? is mortar strong enough to hold the joists/floor? The room is about 13foot wide and 18 foot long and he has used 7x3 joists.

Untitled

• newuser1
• 26 Apr 2013
• 1

Untitled

• newuser1
• 26 Apr 2013
• 1

Many thanks for your help

 

[tony1851]

Two inch mortar seems a bit thick but once its hardened, there wouldn't be a problem. Nothing wrong with putting old bricks between the joists; it's when they put nothing between that there should be concerns.

 

[newuser1]

thanks tony1851

As shown in the first pic, the 2 inch mortar continues all the way along the 18ft wall so I was worried maybe its not strong enough or over time it may get weaken and crumble due to its thickness.

Do you think also that where the joists are placed there should be something extra to support each joist maybe a pieces of slate/bricks or something or am I worried about nothing and its fine.

Spending 50 odd grand on an extension is a big deal for me and maybe I'm looking at very small imperfections and magnifying them too much but that's because my last builder did me over with some shoddy work so I get worried at the slightest now

 

[banjodeano]

To be honest newuser, i am with you on this one, although i am not a builder by trade, i would not be happy with the situation, it should be resting on solid brick, what if the mortar is not of the correct mix.?

 

[tony1851]

Yes, ideally the joists should be on some thinner material, such as slate, bedded in thinner mortar joints, but once the mortar has set, there shouldn't be a problem.
Is it actually a 2" thick solid bed of mortar, or are the joist-ends actually supported on hard material,and the builder perhaps run a strip of mortar over it to tidy it up?
If he had set the joists on pure mortar, it would have probably squeezed out before it set and the joists might have ended up un-even.

 

[noseall]

B.C. in Staffs would have issues with regular bricks being used along side more thermally efficient blocks.

They would insist you use lightweight coursing bricks or cut down aerated blocks and would not allow the use of regular bricks in this location.

The extra deep mortar is just lazy. I would not like it myself.

 

[newuser1]

Thank you all for your input

I haven't questioned the builder yet whether he has put something underneath to support each joist but I wanted to ask some expert advice here before I confront him.

The mortar that runs along the bottom of the old bricks is around 2" thick but some of the mortar underneath the joists seems slightly more than 2". Its all a question of whether the weight of the room above would cause an issue over time. I don't know whether mortar deteriorates in strength over time although other materials may also deteriorate but surely the bricks and blocks are much stronger than hardened mortar?

I had a quick chat with my architect but his knowledge is more theoretical than practical but he also suggested he support each joist with something underneath or if block/bricks are too high he should make cuts in the blocks/bricks to ensure the joists are resting on solid material.

I'll ask the builder and see what he has to say about this. No doubt he will say its not a problem as his not going to re-do something his done already unless I pay him extra of course.

 

[catlad]

You will probably find the joist are packed with something solid and he has just used a bit of cement to finish it off.

 

[AronSearle]

B.C. in Staffs would have issues with regular bricks being used along side more thermally efficient blocks.

I think this is an important point, and would agree.

 

[^woody^]

I had a quick chat with my architect but his knowledge is more theoretical than practical

It's neither by the sound of his answer, and his solution is nonsense

Standards wise, it breaches a few and goes against good practice in terms of building in masonry.

Plus, use of the thick joint and different bricks is a potential condensation causing issue when the work is complete and room used

In terms of quality, I can't think for the life of me why a tradesman would do that. He should have cut a block. It's plain lazy, and if that's indicative of his work, then what else is he doing badly?

But all said and done, it wont fail under normal circumstances

 

[tony1851]

No, it's not good practice but it's not worth bothering about.

The bulder wouldn't have just set the joists on 2" thick mortar because it would have squeezed out. There'll be more solid material underneath.

As regards the bricks between the joists; yes, it's lazy but condensation shouldn't be an issue. The temp. difference won't be that great because of the
cavity fil on the other side, and quite often it stays warm betwen the floor joists because of heating pipes.

There's no point now in getting the builder to re-do all this because he'll just save the extra expense somewhere else, but you do need to let him know that you are keeping an eye on things.

 

[^woody^]

The bulder wouldn't have just set the joists on 2" thick mortar because it would have squeezed out. There'll be more solid material underneath.

Unless he laid the bed, squared it off and left it a while, or over night to go off

As for the brick the temperature difference does not have to be that great, just a fraction of a degree. The fact is, there is a wall of one material, and a patch of a different material. That's all it takes and that is why there are various building standards. The cavity wall insulation makes no difference to the formation of condensation

If I was the OP I would give the builder the option of re-doing it properly, or making a deduction from the bill to reflect the OP's risk. If I was managing it, it would be re-done with no arguments

 

[tony1851]

The bulder wouldn't have just set the joists on 2" thick mortar because it would have squeezed out. There'll be more solid material underneath.

Unless he laid the bed, squared it off and left it a while, or over night to go off

In which case it will have hardened anyway. The load under each joist-end will not be that great. if its a 12ft span floor, load at each bearing would be
c. 1.5 kN, on a 100 x 50 bearing = 0.3N/m^2 = nothing.



With condensation, its about risk, and the risk in that position is negligible. Similar issues arise where you get dense concrete padstones or lintels, for example.

 

[^woody^]

loading too

As for condensation risk, that

 

[tony1851]

Woody, it's quarter-past eleven and past my bed time. Night-night.