Brickwork under suspended floor

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Barry_Convex
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Brickwork under suspended floor

Post by Barry_Convex » Thu Aug 10, 2017 9:18 pm

So, I have a suspended floor with only one air brick. This has caused damp rot of timbers. It's been repaired way back in history and needs doing again. I'll be adding 3 more air bricks to slow future issues.

I'd like advise on improving the state of the brickwork beneath floor level though. It's dropping quite badly due partly to powering mortar but also in part due to a line of rotten timber within the mortar line (in photo).

So, why is there a line of rotten timber in the mortar?

And what's the best approach to repair the brick work?

Ta very much.
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Re: Brickwork under suspended floor

Post by Barry_Convex » Thu Aug 10, 2017 9:21 pm

Barry_Convex wrote:So, I have a suspended floor with only one air brick. This has caused damp rot of timbers. It's been repaired way back in history and needs doing again. I'll be adding 3 more air bricks to slow future issues.

I'd like advise on improving the state of the brickwork beneath floor level though. It's dropping quite badly due partly to powering mortar but also in part due to a line of rotten timber within the mortar line (in photo).

So, why is there a line of rotten timber in the mortar?

And what's the best approach to repair the brick work?

Ta very much.
Erm, don't seem to be able to attach the photo...


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Re: Brickwork under suspended floor

Post by Barry_Convex » Thu Aug 10, 2017 9:22 pm

Barry_Convex wrote:So, I have a suspended floor with only one air brick. This has caused damp rot of timbers. It's been repaired way back in history and needs doing again. I'll be adding 3 more air bricks to slow future issues.

I'd like advise on improving the state of the brickwork beneath floor level though. It's dropping quite badly due partly to powering mortar but also in part due to a line of rotten timber within the mortar line (in photo).

So, why is there a line of rotten timber in the mortar?

And what's the best approach to repair the brick work?

Ta very much.
Here's the photo
DSC_0803.JPG
DSC_0803.JPG (84.68 KiB) Viewed 1320 times
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ayjay
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Re: Brickwork under suspended floor

Post by ayjay » Thu Aug 10, 2017 9:45 pm

Barry_Convex wrote: So, why is there a line of rotten timber in the mortar?
In your pic it looks like it used to be the plate that the joists are sitting on.
One day it will all be firewood.
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Re: Brickwork under suspended floor

Post by davyp1 » Fri Aug 11, 2017 7:58 am

You are correct in that you need at least three more air-bricks to help create 'underfloor cross-ventilation.

I agree with ayjay that the rotten timber is indeed the Wallplate of the supporting sleeper wall.
In addition it is obvious that the sleeper wall has not been constructed with any 'pigeon holes' to permit cross ventilation.
Also, the wall plate has rotted because the sleeper wall does not appear to have a DPC in it's construction.

You will need to strip back the flooring and joists, then replace the sleeper walls and wall-plates to include both pigeon-holes (for cross-ventilation) and a DPC which is tied in with the DPC present in your external walls.
I also think it would be prudent when the sleeper walls are stripped out, to check the integrity of the sleeper-wall foundations.

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Re: Brickwork under suspended floor

Post by Barry_Convex » Fri Aug 11, 2017 8:11 am

Sounds serious...

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Re: Brickwork under suspended floor

Post by Barry_Convex » Fri Aug 11, 2017 8:24 am

I'm kinda surprised that timber was used there, but then again the joists are there too.

The kitchen has been concreted in so there did used to be cross ventilation, but no channels were put in the concrete to retain this. So yes, this will definitely be addressed but it will have to be side and front vents.

The floor and joists are already mostly stripped so going one step further is no bother. The joists have already had work done on them including a central beam which will hold them in place if I take the rotten ends off.

So what would be the sequence of events?
Remove any loose bricks, preferably down to where I can find the exterior DPC?
Then rebuild on a layer of slate or simple modern membrane? Creating saddles for joists and holes for vents as I go?

Will I need to support the wall in any way or only do small sections at a time?

I'll dig out a wider photo too.

Thanks

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Re: Brickwork under suspended floor

Post by Barry_Convex » Fri Aug 11, 2017 8:26 am

Wider view Image

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Re: Brickwork under suspended floor

Post by davyp1 » Fri Aug 11, 2017 2:06 pm

Seeing the 'bigger picture' my assumption that the first photo was of a 'sleeper wall' was incorrect!
I realise now that it is of an exterior wall, also that the wallplate (the rotten timber) will have to be removed.
I would also stipulate that you do not replace this timber in the exterior walls; but you do introduce a DPC under the joists.
What is the joist span in that room? I also wonder if their is a sleeper wall ?
I will comment further after your responce.

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Re: Brickwork under suspended floor

Post by wes56 » Fri Aug 11, 2017 5:20 pm

can you post photos of whats now existing and of the outsideof the wall. cut all rotten ends off and pull out alltherotten plate in the wall.all of it
you can cut pockets in the bricks for the joist tailsto bare on, or you can build a short wall below the joists. cap the new bolt-ons with dpc material,no wood should touch any bricks.
Replace short sections of brickworkif you go that roote. let it dry then replace the next section.
bedead carefull under the door threshold or you can give yourself a big hedake.
use a span table to work out the joist spans. level all joits two ways. the old repair sistering stuff was done well wrong
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Re: Brickwork under suspended floor

Post by Barry_Convex » Sat Aug 12, 2017 9:12 am

I'm away for the week so can't take any new photos right now.

There is no sleeper wall, the joists go into a central spine wall which separates the two ground floor rooms - the other one having been concreted in. But a beam has been propped beneath the middle of the joists which, although bodged, is firming the floor up well, considering the loose ends.

The span is around 3.5m

Exterior is pebble dashed with the bottom 1 foot rough rendered proud by half an inch to create a skirt. So the exterior bricks aren't visible.

1. I'm happy to redo the sleeper /central beam properly since it seems to be serving a purpose. Slabs, slate, bricks and mortar to create 3 columns?

2. Yeah, I'll redo the sistering - what's recommended : an equal width bolted on one side or half width bolted on both sides?

3. Is there any point using blue bricks here or how do I introduce a DPC into the wall. (as well as using DPM on the Joist ends)?

Any further advise VERY much appreciated.

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Re: Brickwork under suspended floor

Post by Barry_Convex » Sat Aug 19, 2017 9:23 am

Any further advise on the DPC in the brickwork?
Slate layer?
Engineering bricks?
Polythene?

Ta!

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Re: Brickwork under suspended floor

Post by Barry_Convex » Sun Sep 03, 2017 7:46 pm

Barry_Convex wrote:Any further advise on the DPC in the brickwork?
Slate layer?
Engineering bricks?
Polythene?

Ta!

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Sooo, I've gone the route of replacing the saddle with engineering bricks...Image

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Re: Brickwork under suspended floor

Post by Barry_Convex » Wed Sep 06, 2017 10:03 pm

Tadah! Finally, sorted.
Woodworm treated, sistered and bricked back up with engineering bricks and 3 period cast iron air bricks.

Now for the rest of the house... Image

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