Hi, we are converting the loft in our late 19th century semi detached house and will be putting beams into the party wall to support the new floor. We spoke to the neighbour to get party wall consent but he is concerned that the lime mortar in the wall has become friable due to its age and that the beams will damage the wall. Neither our architect or structural engineer mentioned this and I haven't heard of it happening before in loft conversions. Is his worry a valid one - does anyone know of this happening?
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Will party wall mortar support loft conversion beams?
- Thread starter Jo R
- Start date
andrew gayton
Member
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- 527
with a suitable padstone bearer for either end of the beam, it should be ok provided the walling is generally sound.................. what is the substrate? brick.............rubble..................timber??
andrew gayton
Member
- Messages
- 527
sorry! 'substrate' what the walling is made from under the plaster covering/s..................
andrew gayton
Member
- Messages
- 527
ok................. assumint that the bearing beam is a steel section where you will either sit the new joists on or sit them within a channel, you will need a min of 100mm bearing on a concrete pad stone or engineering bricks bedded on a drypack mortar. easy-peasey. if however there is concern about the friable nature of the walling, the immediate areas can be reinforced with helif*x etc etc. that make sense?
andrew gayton
Member
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- 527
sorry, sp..... 'assuming'
Thankyou.. you've made it very clear. I can look into the reinforcement.
I may speak to the structural engineer again as I need to know if the mortar really is crumbling or if it is just my neighbour being overly cautious. I had the impression that mortar only crumbled on outside walls - I take it it breaks down in interior walls too?
I may speak to the structural engineer again as I need to know if the mortar really is crumbling or if it is just my neighbour being overly cautious. I had the impression that mortar only crumbled on outside walls - I take it it breaks down in interior walls too?
andrew gayton
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define 'crumbly' i have known of people say mortar is crumbly because it comes out with a hammer and bolster.............
.................... as i said, 100mm bearing is the minimumm......... if you can achieve more, this will help a great deal.
.................... as i said, 100mm bearing is the minimumm......... if you can achieve more, this will help a great deal.
I haven't even been in the loft so far but I will check the mortar and report back. We have never had a house before in which we had to deal with mortar deterioration so I'm not entirely sure what our neighbour means by crumbly! The mortar seems solid enough on the outside of the houses, but I suppose this could have been re-pointed.
Thanks for the information on bearings, I will pass all this on to my partner, who will be able to make use of it!
Thanks for the information on bearings, I will pass all this on to my partner, who will be able to make use of it!
andrew gayton
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- 527
no problem!
chuckey
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- 883
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- wenslydale
have a look in your loft for purlins set into the party wall, if there is one there you can be assured of a good load bearing wall. If there are no purlins set into it, the wall may be of poor construction, broken bricks ,voids etc. It will still take a formidable load on it providing there are no side loads and the load is distributed on it (pad stone). Look at how and where the existing ceiling joists are fitted into the wall. If the joists are already are set into the wall, point this out to your neighbour, so de facto the wall is OK!
Frank
Frank
Stephen
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- 199
- Location
- Bishop's Stortford, Herts
Lime mortar is soft especiall compared t modern cement mortars, but as it ages it generally becomes stronger not weaker. It would be wrong to assume that lime mortar is weak or incapable of bearing loads simply because it is sot or the surfaces are 'crumbly'.
That said it can deteriorate if water has got in (roof leaks, etc) in the past. Further, sometimes the mortar originally used was poor anyway (especilly in a loft). I will be for your professional adviser to consider whether the lime mortar generally is capable of bearing te loads intended, but do not let anyone tell you that because it is lime it is inevitably weak.
Lime does not have the same compressive strength as cment mortar, but it ca still bear the normal loads of a house, etc. However, spot loads are not a good idea (i.e. a beam end). Therefore, some form of 'spreader' is required and the suggestion to create a padstone is fine, or you could bed a steel RSJ or channel in the wall instead (probably quicker and easier than creating a padstone in-situ). The beam end bedded into the wall will need to bear at the mid point of the padstone or steel bearer. This is fairly standard practice and would usually be necssary even in modern houses with cement mortar because spot loads such as a beam end for a loft conversion are not a good idea in any wall.
That said it can deteriorate if water has got in (roof leaks, etc) in the past. Further, sometimes the mortar originally used was poor anyway (especilly in a loft). I will be for your professional adviser to consider whether the lime mortar generally is capable of bearing te loads intended, but do not let anyone tell you that because it is lime it is inevitably weak.
Lime does not have the same compressive strength as cment mortar, but it ca still bear the normal loads of a house, etc. However, spot loads are not a good idea (i.e. a beam end). Therefore, some form of 'spreader' is required and the suggestion to create a padstone is fine, or you could bed a steel RSJ or channel in the wall instead (probably quicker and easier than creating a padstone in-situ). The beam end bedded into the wall will need to bear at the mid point of the padstone or steel bearer. This is fairly standard practice and would usually be necssary even in modern houses with cement mortar because spot loads such as a beam end for a loft conversion are not a good idea in any wall.
We checked the mortar and it doesn't appear to have deteriorated, though I'll check with the structural engineer to get a professional opinion for my neighbour. The beams in the loft are not currently set into the wall unfortunately Frank. We will be using padstones rather than bedding an RSJ into the wall but I'll mention this idea. Will also look for purlins. Thank you very much for all your advice!